AU657549C - Michellamines useful as antiviral agents, composition and method of treatment - Google Patents

Description

MICHELLAMINES USEFUL AS ANTIVIRAL AGENTS,

COMPOSITION AND METHOD OF TREATMENT

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to compounds which exhibit antiviral activity, methods for isolating the compounds from plants, and methods for using the compounds. More specifically, the present invention relates to: isolation and identification of new chemical compounds; and compositions containing the same. The compounds of the present invention exhibit advantageous pharmacological, toxicological and antiviral properties, such as, for example, inhibition of the cytopathic effects of the human immunodeficiency virus (HIV), which is implicated as a causative agent of AIDS (Acquired Immune Deficiency Syndrome).

Description of Related Art

AZT is now the only commercially available, known clinically active agent currently used widely in the therapy of AIDS. While extremely useful in antiviral therapy, AZT is limited in its use due to its toxicity and an insufficient therapeutic index to make it adequate for therapy. Thus, new classes of antiviral agents to be used alone or in combination with AZT and other agents are needed urgently for effective antiviral therapy against HIV. It is also especially important to have new agents which have antiviral activity against HIV-1 as well as HIV-2. SUMMARY OF THE INVENTION

The present invention is directed to a compound having the formula:

or

in substantially pure form (hereinafter "michellamines"); or a pharmacologically acceptable salt thereof.

The present invention is also directed to derivatives of the michellamines having the formula:

wherein R¹ and R⁶ are the same or different and are each C₁-C₆ alkyl, R¹¹CO-, or R¹¹SO₂- wherein R¹¹ is C₁-C₆ alkyl or aryl;

R², R³, R⁴, R⁷, R⁸ and R⁹ are the same or different and are each C₁-C₆ alkyl, R¹¹CO-, R¹¹SO₂- wherein R¹¹ is defined above;

R⁵ and R¹⁰ are C₂-C₆ alkyl,

wherein R₁₂ is C₁-C₆ alkyl or R¹³CO- or

R¹³SO₂-, wherein R¹³ is C₁-C₆ alkyl or aryl;

and wherein the ring H position at 1', 3', 7', 4 and 7 can be substituted with a halogen, nitro, amino, hydroxyl, thiol or cyano group; or a pharmacologically acceptable salt thereof;

The present invention is also directed to a method of isolating the michellamines of Figure 1 from Ancistrocladus abbreviatus which comprises the steps of:

(a) extracting dried plant material with an organic solvent to obtain a crude extract;

(b) acid-base partitioning said crude extract to obtain a crude organic base fraction; (c) subjecting said crude organic base fraction to centrifugal partition chromatography; and

(d) isolating said michellamines with an amino-bonded phase HPLC column.

Another aspect of the invention is directed to a method of the interconversion of either of michellamines A or B into a mixture of michellamines A, B and C, which comprises:

(a) dissolving either of michellamines A or B in an organic solvent; and

(b) reacting said michellamines A or B with a base. A further aspect of the invention is directed to an antiviral composition which comprises an antiviral effective amount of at least one michellamine A, B or C, and a pharmacologically acceptable carrier.

.Another aspect of the invention is directed to an antiviral composition which comprises an antiviral effective amount of at least one compound according to the michellamine derivatives described, supra, and a pharmaceutically acceptable carrier.

Either of the antiviral compositions can further include an antiviral effective amount of AZT and/or other known antiviral agents.

The present invention is also directed to a method of treating a viral infection which comprises administering to a patient in need thereof, an antiviral effective amount of at least one compound of michellamines A, B or C; and to a method of treating a viral infection which comprises administering to a patient in need thereof, an antirival effective amount of at least one of the michellamines A, B or C derivatives.

The method of the present invention also comprises co- administering an antiviral effective amount of AZT and/or other known antiviral agents; together with at least one of michellamine A, B or C, or derivatives thereof.

The compounds described herein have not been reported heretofore in the literature, nor have methods for isolation of same from any source been described, nor have any antiviral or other biological activities been reported for same, nor have methods of preparation and medical use of compositions of same been presented heretofore.

Further scope of the applicability of the present invention will become apparent from the detailed description and drawings provided below. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated further in the accompanying drawings wherein:

Figure l illustrates the structures of michellamines A, B and C. The ring-position numbering scheme is shown only for michellamine A, but is the same for michellamines B and C.

Figures 2 A-D, show anti-HIV-1 activity of michellamine A (free base). Figures 2A, 2B and 2C, show the effects of a range of concentrations of michellamine A upon uninfected CEM-SS cells (o) and upon CEM-SS cells infected with HIV-1 (●), as determined after 6 days in culture; Fig. 2A depicts the relative numbers of viable CEM-SS cells, as assessed by the BCECF assay; Fig. 2B depicts the relative DNA content of the respective cultures; Fig. 2C depicts the relative numbers of viable CEM-SS cells, as assessed by the XTT assay. Fig. 2D shows the effects of a range of concentrations of michellamine A upon indices of infectious virus or viral replication; these indices include viral reverse transcriptase activity (▲) , production of viral core protein p24 (♦) and syncytium-forming units (■). In Figs. 2A, 2B and 2C, the data points are represented as the percent of the uninfected, non-drug treated control values. In Fig. 2D the data points are represented as the percent infected, non-drug treated control values.

Figures 3 A-D, show anti-HIV-1 activity of michellamine A (HBr salt). Figures 3A, 3B and 3C show the effects of a range of concentrations of michellamine A (HBr salt) upon uninfected CEM-SS cells (o) and upon CEM-SS cells infected with HIV-1 (e), as determined after 6 days in culture; Fig. 3A depicts the relative numbers of viable CEM-SS cells, as assessed by the BCECF assay; Fig. 3B depicts the relative DNA content of the respective cultures; Fig. 3C depicts the relative numbers of viable CEM-SS cells, as assessed by the XTT assay. Fig. 3D shows the effects of a range of concentrations of michellamine A (HBr salt) upon indices of infectious virus or viral replication; these indices include viral reverse transcriptase activity (▲) , production of viral core protein p24 (♦) and syncytium-forming units (■). In the Figs. 3A, 3B and 3C the data points are represented as the percent of the uninfected, non-drug treated control values. In Fig. 3D, the data points are represented as the percent infected, non-drug treated control values.

Figures 4 A-D show the anti HIV-1 activity of michellamine B (free base). Figs. 4A, 4B and 4C, show the effects upon a range of concentrations of michellamine B upon uninfected CEM-SS cells (o) and upon CEM-SS cells infected with HIV-1 (#) as determined after 6 days in culture; Fig. 4A depicts the relative numbers of viable CEM-SS cells, as assessed by the BCECF assay; Fig. 4B depicts the relative DNA content of the respective cultures; Fig. 4C depicts the relative numbers of viable CEM-SS cells, as assessed by the XTT assay. Fig. 4D shows the effects of a range of concentrations of michellamine B upon indices of infectious virus or viral replication; these indices include viral reverse transcriptase activity (▲), production of viral core protein p24 (♦) and syncytium-forming units (■). In Figures 4A, 4B and 4C, the data points are represented as the percent of the uninfected, non-drug treated control values. In Fig. 4D the data points are represented as the percent of infected, non-drug treated control values.

Figures 5 A-D, show anti-HIV-1 activity of michellamine B (HBr salt). Figs. 5A, 5B and 5C, show the effects of a range of concentrations of michellamine B (HBr salt) upon uninfected CEM-SS cells (o) and upon CEM-SS cells infected with HIV-1 (●), as determined after 6 days in culture; Fig. 5A depicts the relative numbers of viable CEM-SS cells, as assessed by the BCECF assay; Fig. 5B depicts the relative DNA content of the respective cultures; Fig. 5C depicts the relative numbers of viable CEM-SS cells, as assessed by the XTT assay. Fig. 5D shows the effects of a range of concentrations of michellamine B (HBr salt) upon indices of infectious virus or viral replication; these indices include viral reverse transcriptase activity (▲), production of viral core protein p24 (♦) and syncytium-forming units (■). In Figs. 5A, 5B and 5C the data points are represented as the percent of the uninfected, non-drug treated control values. In Fig. 5D, the data points are represented as the percent of infected, non-drug treated control values.

Figures 6A and 6B, show anti-HIV-2 activity of michellamine A (free base and HBr salt). Fig. 6A shows the effects of a range of concentrations of michellamine A (free base) upon uninfected MT-2 cells (o) and upon MT-2 cells infected with HIV-2 (●) as determined using the XTT assay after 6 days in culture. The open bars show the corresponding supernatant reverse transcriptase activities. Fig. 6B shows the effects of a range of michellamine A (HBr salt) concentrations upon uninfected MT-2 cells (o) and upon MT-2 cells infected with HIV-2 (●) as determined using the XTT assay after 6 days in culture. The open bars show the corresponding reverse transcriptase activities. In both graphs, all data points are represented graphically as the percent of their respective controls. Figures 7A and 7B show anti HIV-2 activity of michellamine B (free base and HBr salt) . Fig. 7A shows the effects of a range of concentrations of michellamine B (free base) upon uninfected MT-2 cells (o) and upon MT-2 cells infected with HIV-2 (●) as determined using the XTT assay after 6 days in culture. The open bars show the corresponding supernatant reverse transcriptase activities. Fig. 7B shows the effects of a range of michellamine B (HBr salt) concentrations upon uninfected MT-2 cells (o) and upon MT-2 cells infected with HIV-2 (●) as determined using the XTT assay after 6 days in culture. The open bars show the corresponding supernatant reverse transcriptase activities. In both graphs, all data points are represented graphically as the percent of their respective controls.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Examples of pharmacologically acceptable salts include HBr, HCl, oxalate, citrate, tartrate salt and the like.

By C₁-C₆ alkyl is meant straight or branched chain C₁-C₆ alkyl groups. Examples include, but are not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tertiary-butyl, n-pentyl, iso-pentyl and n-hexyl.

By aryl is meant an organic radical derived from an aromatic hydrocarbon. An example of an aryl group is phenyl.

By aliphatic is meant organic radical derived from an open hydrocarbon chain. Examples of aliphatic radicals include alkanes, alkenes and alkynes. Specific examples of aliphatic radicals which can be used in the present invention include, but are not limited to, C₁-C₆ alkyl radicals, straight or branched.

Of the viral infections that can be treated, examples include, but are not limited to, Type C and Type D retroviruses, HTLV-1, HTLV-2, HIV-1, HIV-2, feline leukemia virus, simian immunodeficiency virus, murine leukemia virus, bovine leukemia virus, equine infections, anemia virus, avian sarcoma viruses, such as rous sarcoma virus and the like, hepatitis type A, B, non A/non B, herpes viruses type 1 and 2, cytomegaloviruses, influenza viruses, arboviruses, varicella viruses, measles, mumps and rubella viruses.

Ancistrocladus abbreviatus. (Airy Shaw), from which an extract was obtained, is one of approximately 20 species of plants from the family Ancistrocladaceae. A detailed description of the plant can be found in: "A Dictionary of Flowering Plants and Ferns" [Willis, J.C.: Shaw, A.K. (ed.), Cambridge University Press, Cambridge, England, 1973, p. 61.]. The genus is found principally in Asia, Malaysia and West Africa. The plant material for the present study was collected on March 25, 1987, in Southwest Province, Korup National Park, Cameroon by the Missouri Botanical Garden. The plant was collected at an altitude of 60 meters, at a location of latitude 5.03'S and longitude 8.83°E.

Isolation of the Michellamines from Extracts of the Plant Genus Ancistrocladus

A variety of methods can be used to isolate the michellamines. Among these methods are extraction, solvent-solvent partitioning, centrifugal partition chromatography, gel permeation chromatography and HPLC with a variety of bonded phases. The isolation of the compounds can be monitored by UV, TLC and anti-HIV bioassay.

Overall Isolation Procedure for Michellamines from .Ancistrocladus abbreviatus

This procedure is of a scale to accommodate an initial starting amount of approximately 1/2 kilogram of the air- dried plant material consisting of leaves, stems and twigs. This plant material is first ground up and extracted with 1:1 MeOH:CH₂Cl₂ followed by a second extraction with methanol. These initial crude organic extracts typically amount to a total of approximately 8-10% of the mass of the original crude extract. This second extract then is dissolved in 5% aqueous HC1 and extracted with CHCl₃. The aqueous layer is then made basic with concentrated NH₄OH to a pH of 10-11; it is then extracted with 4:1 CHCl₃:MeOH and then with 1:1 MeOH:CHCl₃ to give a total of about 0.5-1.0g of basic extract after removal of the solvent. The extract is then dissolved in the lower phase of a 5:5:3

(CHCl₃:MeOH:0.5% aqueous HBr) biphasic solvent system and placed on a Sanki CPC operating in the descending mode.

The effluent is monitored at 270 nm. The final peak to come off in descending mode contains the HBr salts of both michellamine A and B plus a trace of C. After removal of the solvent, this mixture typically comprises a total mass of about 200-300 mg. The mixture is further separated with amino bonded phase HPLC using (43:7) [CHCl₃:MeOH

0.075%(NH₄)₂CO₃] as the solvent. Using this general procedure, the overall yield of michellamines from crude organic extract is about 0.5-2% for michellamine A and 2- 10% for michellamine B. Michellamine C is isolated in trace amounts following the same procedure.

EXAMPLE 1

The leaves and stems of dried Ancistrocladus abbreviatus (449g) were ground in a Wiley mill and extracted with 1:1 MeOH-CH₂Cl₂ in a Kimax percolator. The ground material was allowed to steep in the solvent overnight. The solvent was removed by filtration and evaporated at reduced pressure to give 36.62 g of crude organic extract.

A portion (2.107 g) of this extract was suspended/dissolved in 330 ml of 5% aqueous HCl and extracted with four 100 ml aliquots of CHCl₃. The extracts were combined and the solvent removed at reduced pressure to give 0.657g of extract. A primary anti-HIV assay was performed according to the procedure set forth in Weislow, 0. , et al.: J. Natl. Cancer Inst. 81:557-586, 1989, and the material was found to be inactive.

The remaining aqueous layer was treated with concentrated NH₄OH until the pH of the solution was between 10 and 11. The basic aqueous phase was extracted with five 100 ml aliquots of 4:1 CHCl₃:MeOH. The extracts were combined and the solvent removed at reduced pressure to give 0.3195g of extract. An anti-HIV assay was run according to the procedure set forth in Weislow et al., supra, and the material was found to be active.

The remaining aqueous layer was extracted further with three 100 ml aliquots of 1:1 MeOH:CHCl₃. The extracts were combined and the solvent removed at reduced pressure to give 0.2534g of extract, and which was again tested according to the same assay (Weislow, supra) and the material was found to be active.

NMR and TLC analyses of the two extracts indicated that both samples contained the same compounds. An aliquot of extract from the 4:1 CHCl₃:MeOH procedure (264.1 mg) was dissolved in a small amount of the lower phase of a 5:5:3 MeOH-CHCl₃-0.5% aqueous HBr biphasic system. This sample was injected into a Sanki centrifugal partition chromatograph (CPC) operating in the descending mode with 12 analytical cartridges (400 rpm, 3.0 ml/min). The effluent was monitored at 270 nm using a Linear UV/Vis 200 monitor. Eight fractions were collected (A-H) while the instrument was operating in the descending mode and a ninth fraction collected (I) when the instrument operation was reversed to the ascending mode. Fractions A, C, E and F were inactive in the anti-HIV assay, supra. Fractions B (14.4 mg), D (9.0 mg) and I (31.8 mg) showed relatively little activity in the anti-HIV assay, supra. The majority of the anti-HIV activity was found in fractions G (72.7 mg) and H (45.4 mg).

Fraction H (45.4 mg) was dissolved in 500 μl of CHCl₃-MeOH (43:7) and injected onto a Waters Delta Prep HPLC using a Rainin Dynamax NH₂ column (21.4 mm x 250 mm equipped with a guard column). The sample was eluted with CHCl₃- MeOH/0.075% (NH₄)₂CO₃ (43:7) at a flow rate of 13 ml/min and monitored at 260 nm. Six fractions were collected and tested for HIV-inhibitory activity. Fractions 1 (retention time = 10 min., 1.1 mg), 2 (retention time = 19 min., 4.3 mg), 4 (retention time = 26 min., 4.6 mg) and fraction 5 (retention time = 31.5 min., 1.0 mg) were found to be inactive. Fraction 3, proved to be michellamine A (retention time = 22 min., 10 mg); fraction 6 proved to be michellamine B (retention time = 36 min., 14.4 mg). Their chemical and spectral characteristics are set forth herein below.

Fraction G was treated in a similar manner, except that it was dissolved in 1.5 ml of solvent and placed on the column in three 500 μl injections. From this sample, 5.0 mg of michellamine A and 39.5 mg of michellamine B were obtained. 3.0 mg of an inactive, unidentified compound were also collected.

The sample isolated from the MeOH-CHCl₃ (1:1) extract described above (251 mg) was placed on the Sanki CPC under the same conditions as the 4:1 extract. In this case, seven fractions were collected while the instrument was operated in the descending mode (A-G) and one fraction collected during the ascending mode (H).

Fractions A, B, C, D and H were inactive in the anti-HIV assay while E, F, and G were all active. Preparative HPLC of Fraction E (72.4 mg) under the identical conditions as above afforded 0.8 mg of michellamine A, 44.5 mg of michellamine B and 6.3 mg of an inactive tetrahydroisoquinoline compound. Fraction F (18.8 mg) afforded 2.8 mg of michellamine A and 8.1 mg of michellamine B along with two minor inactive compounds (< 2 mg). Fraction G (18.2 mg) afforded 10.1 mg of michellamine A and 2.1 mg of an unknown inactive substance. A third, minor compound, michellamine C, was isolated on one occasion as a shoulder on the michellamine B chromatographic peak. It has not been encountered in subsequent, more rapidly processed material.

The overall yield of the active fractions from starting crude extract was 1.4% michellamine A and 5.0% michellamine B. Chemical Structures of Michellamines A, B, and C

An in vitro anti-HIV screening assay, according to the procedure set forth in Weislow, 0. et al., supra, initially disclosed AIDS-antiviral activity in the CH₃OH-CH₂Cl₂ (1:1) extracts of Ancistrocladus abbreviatus. Prelminary fractionation established that the active constituents were basic alkaloids. The crude alkaloid fraction, obtained by acid-base partitioning, was subjected to centrifugal partition chromatography (CHCl₃-CH₂OH-0.5% HBr/H₂O, 5:5:3); elution with the lower phase gave four fractions. Fraction 4 yielded two active compounds, related as atropisomers to which were given the names michellamines A and B (Figure 1), upon HPLC on an amino-bonded phase semi-preparative column [CHCl₃-0.075% (NH₄)₂CO₃/CH₃OH, 43:7].

Mass spectral analyses, via plasma desorption mass spectrometry (²⁵²Cf PDMS) , demonstrated that the two compounds had identical molecular weights (m/z 756). The molecular formula was established as C₄₆H₄₈N₂O₈ by accurate-mass, fast atom bombardment mass spectrometry.

The family Ancistrocladaceae is well known as a source of naphthalene-tetrahydroisoquinoline alkaloids [Bringmann G.: The Naphthyl Isoquinoline Alkaloids, in The Alkaloids, Vol. 29, A. Brossi, ed., Academic Press, New York, 1986, pp. 141-184; Ruangrungsi N, et al: J Nat Prod, 48: 529-534, 1989, and references cited therein]. The mass spectral data and the complex NMR spectra of the isolated compounds suggested that these antiviral compounds were dimeric relatives of the known Ancistrocladaceae alkaloids.

The NMR data for michellamine A are provided in Table

1.

TABLE 1. NMR DATA FOR MICHELLAMINE A Carbon # δ (# attached H) ¹H δ Multiplicity) J (Hz)

1 49.5 (1) 4.64 q 6.5

3 45.2 (1) 3.54 ddq 11.8,4.3,6.5

4 33.1 (2) (e)2.69 dd 18.6,4.3; (a)2.05 dd

18.6,11.8

4a 133.1 (0)

5 120.3 (0)

6 156.9 (0)

7 102.0 (1) 6.40 (s)

8 155.4 (0)

8a 113.1 (0)

1' 119.1 (1) 6.75 (s)

2' 137.6 (0)

3' 108.0 (0) 6.84 (s)

4' 158.1 (0)

4a' 115.2 (0)

5' 152.2 (0)

6' 119.0 (0)

7« 134.8 (1) 7.30 (s)

8' 124.1 (0)

8a' 136.6 (0)

OMe 57.1 (3) 4.10 (s)

Me-3 19.4 (3) 1.16 q 6.5

Me-1 18.4 (3) 1.57 q 6.5

Me-2' 22.1 (3) 2.33 (S)

¹³C (125 MHz) and ¹H (500 MHz) NMR spectra of the HBr salt were recorded in d₄-methanol. # attached H determined from DEPT experiments.

Other spectral data and other characteristics for michellamine A are as follows: MP=220°C (dec);[α]_D = -10.5°, [α]₃₆₅ = +65.7° (C=0.38, MeOH) ; FAB-MS: m/z 757.342 (MH+, calc'd for C₄₆H₄₉N₂O₈ 757.3487); λ_max (MeOH) 230 nm (log e=4.4), 262(4.1), 287(3.8), 312(3.8), 331(3.8), 344(3.8); v_max (neat) 3380, 1617, 1584 cm^-1.

The NMR data for michellamine B are provided in Table

2.

TABLE 2. NMR DATA FOR MICHELLAMINE B

Carbon # δ (# attached H) ¹H δ (Multiplicity) J (Hz)

1 49.6, 49.3 (1) 4.44, 4.26 q 6.5

3 45.3, 45.2 (1) 3.27, 3.21 ddq 11.4,4.5,6.5

4 33.9 , 33. 1 (2 ) (eR)2.49 dd 17.5,4.5; (aR)1.86 dd

17.5,11.0

(aS)2.22 dd 17.5,11.0; (eS)2.08 dd 17.5,4.5

4a 133.1, 133.0 (0)

5 120.0, 120.2 (0)

6 156.90, 156.88 (0)

7 102.0, 102.1 (1) 6.34 2H (s)

8 155.54, 155.51 (0)

8a 113.0, 113.2 (0)

1' 119.2, 119.2 (1) 6.77, 6.86 (s)

2 ' 137.60, 137.56 (0)

3' 108.12, 108.11 (1) 6.84, 6.82 (s)

4' 158.0, 158.1 (0)

4a' 115.22, 115.17 (0)

5' 152.2, 153.3 (0)

6' 119.0, 119.1 (0)

7' 136.7, 136.5 (1) 7.28, 7.24 (s)

8' 124.12, 124.10 (0)

8a' 135.2, 134.7 (0)

OMe 57.04, 57.05 (3) 4 . 08 , 4.09 ( S )

Me-3 19.3, 19.3 (3) 1 .05 , 1 . 01 q 6. . 5

Me-1 18.42, 18.40 (3) 1 .52 , 1. 48 q 6. .5

Me-2' 22.1, 22.2 (3) 2.36,2.31 (s)

¹³C (125 MHz) and ¹H (500 MHz) NMR spectra were recorded in d₄-methanol. ¹³C chemical shifts are reported as the HBr salt. ¹H chemical shifts are reported for the free base. The designations (eS,aS) and (aR,eR) refer to the methylene signals on the isoquinoline systems with the 'S' and 'R' stereochemistry at the 5-8' ring juncture; "a" and "e" refer to axial and equatorial. # attached H were determined from DEPT experiments. Other spectral data and other characteristics for michellamine B areas follows: MP=230°C (dec); [α]_D = -14.8°, [α]₃₆₅ = -23.4° (c=0.74, MeOH); FAB-MS; m/z 757.350 (MH+, calc'd for C₄₆H₄₉N₂O₈ 757.3487); UV and IR were identical to those reported for michellamine A.

The presence of only 23 resonances in the ¹³C-NMR spectrum of michellamine A indicated that the two naphthalene-isoquinoline components were equivalent. The structure and relative stereochemistry of the tetrahydroisoquinoline subunit could be discerned readily from ¹H-¹H coupling constant analysis and difference nOe experiments. The H-3 proton served as a linchpin in the analysis (the ring-numbering scheme follows the same scheme as in the Bringmann reference cited above). A pseudoaxial position on the ring was evident from its couplings to the H-4 protons (11.8, 4.3 Hz); a moderate to strong nOe response to the methyl group attached to C-1 established the 1,3 diaxial relationship between the two and therefore the trans relationship between the methyl groups attached to C-1 and C-3. The composition of one ring in the naphthalene system was established through HMQC, HMBC and difference nOe experiments as a pair of meta-disposed protons, with an intervening methyl group and a flanking methoxyl. The remaining ring had a single proton, one hydroxyl group and linkages to two other aryl systems. HMBC and HMQC data suggested a 1,3 relationship of the proton and hydroxyl substituents. The complete substitution of that ring and the relative stereochemistry and conformation of the naphthalene/tetrahydroisoquinoline connection were secured from difference nOe data. Each of the benzylic methylene protons (C-4) of the tetrahydroisoquinoline system exhibited an nOe relationship to different naphthalene protons, H-4e to H-7' and H-4a to H-1'. Thus, the tetrahydroisoquinoline was linked to the naphthalene by a bond from C-5 to C-8'. The naphthalenes, therefore, had to be connected at C-6'. In contrast, the ¹³C-NMR spectrum of michellamine B was comprised of 46 signals. A similar series of NMR experiments provided the same gross structure found for michellamine A. The differences between the two compounds lay in the relative configuration of the ring connections. In michellamine B the C-4 methylene signals appeared as four discreet resonances, and each produced an nOe enhancement of an aromatic proton signal upon irradiation. In one set, the relationships were the same as those in 1: H-4e and H-7', H-4a and H-1'. The relationships were reversed in the other half of the molecule: H-4e and H-1', H-4a and H-7'. As before, the assignments of the protons in the tetrahydroisoquinoline system were established clearly from coupling constants and the nOe data.

A trace amount of a third atropisomer, to which we gave the trivial name michellamine C (Figure 1), also has been encountered. The NMR data for michellamine C are provided in Table 3.

TABLE 3. NMR DATA FOR MICHELLAMINE C

Carbon # ¹H δ (Multiplicity)

1 4.33 q

3 3 .25 m

4 2. 17 , 2.00

7 6.22

1 ' 6.75

3 ' 6.78

7 ' 7. 14

OMe 3.98

Me-3 0.95

Me-1 1.42

Me-2 ' 2.25

NMR spectra were recorded in d₄-methanol. 1H chemical shifts are reported for the free base. Michellamine C appears to have the opposite configuration from michellamine A about the C-5/C-8' bond at both sites in the molecule. Variable temperature NMR experiments failed to show evidence of spontaneous interconversion.

Molecular modeling calculations determined the barrier to rotation about the C-5/C-8' bond in the michellamines to be 81 KJ/mole; in contrast, the calculated barrier for rotation about the C-6'/C-6' bond (51 KJ/mole) was within the range for available thermal energy to enable rotation past the barrier [Still WC, et al: Macromodel. V 2.5, Dept. of Chemistry, Columbia University, NY].

The michellamines are unique molecules in several regards. They are the first dimeric alkaloids of this class to be discovered. None of the known "monomeric" alkaloids have the C-5/C-8' linkage between the two ring systems. Further, they are the most polar compounds in the class, containing more free phenols per monomeric unit than any of the known compounds. The proposed absolute stereochemistry depicted in Figure 1 is based upon literature precedent [Bringmann G., supra, ref. cited above].

EXAMPLE 2. Preparation of HBr Salts of Michellamines

A solution of michellamine B in MeOH was treated dropwise with 9M HBr (2.2 mole equivalents) . After addition was complete, the solvents were evaporated, providing the HBr salt. Other salts of the michellamines have been prepared in a similar manner.

EXAMPLE 3. Method for Interconversion of Michellamines

To a solution of michellamine A (1 mg in 1 ml MeOH-d₄) was added 0.5 ml of 0.5 M NaOD/D₂O· ¹H-NMR analysis indicated a slow conversion of michellamine A to a mixture of michellamines A, B and C (~ 3:3:1) over a period of 7 days. Likewise, michellamine B was converted to the same mixture under identical conditions. HPLC analyses confirmed these results. EXAMPLE 4. Preparation of Michellamine derivatives

Using standard organic chemical methodology, a number of structural modifications of the michellamines can be made for purposes of preparing derivatives of the michellamines which express antiviral activity.

Depending on the stoichiometric amount of the particular reactant, the michellamines can be substituted at one, some or all of the respective positions. For example, when one of the michellamines A, B or C is reacted with a certain amount of CH₃COCl, acetate can be substituted at one, some or all of R², R³, R⁴, R⁷, R⁸ and R⁹. Likewise, when one of the michellamines A, B or C is reacted with a certain amount of benzene sulfonyl chloride, one or both of R¹ and R⁶ can form benzene sulfonamide derivatives.

Examples of these include, but are not limited to:

1. Preparation of ester, sulfonate ester and ether derivatives at one or more of the six phenolic hydroxyl positions in the michellamines (C-5', C-6, C-8).

For preparation of esters or sulfonate ester, michellamine A or B is reacted with an acid halide (RCOX or RS0₂X, where X = Cl, Br or I and R is an Ci-Cg aliphatic or an aromatic radical) in anhydrous pyridine or triethylamine.

Alternatively, michellamine A or B is reacted with an acid (RCO₂H or RSO₃H wherein R is an aliphatic or aromatic radical) and dicyclohexylcarbodiimide in triethylamine to prepare the ester or sulfonate ester.

For preparation of ethers, michellamine A or B is reacted with an alkyl halide (RX, where X = Cl, Br or I and R is an C₁-C₆ aliphatic or aromatic radical) in anhydrous acetone with anhydrous potassium carbonate.

As examples:

2. Removal of the methyl ether group at C-4' to provide a phenolic hydroxyl functionally and/or conversion of that moiety to an ester, sulfonate or other ether.

For cleavage of the methyl ether and conversion to phenolic hydroxyl, michellamine A or B is reacted with BBr₃ or BX₃● (CH₃)₂S in CH₂Cl₂ (where X = F, Cl or Br). The resulting phenol can be converted to esters, sulfonate esters or ethers as described above (in 1).

For example:

3. Preparation of amide or sulfonamide derivatives at one or both amine sites in the michellamines.

For preparation of amide or sulfonamide derivatives, the same procedures described above (in 1) apply. In either case (1 or 3), an appropriate functional group protection strategy (blocking/deblocking of selected groups) is applied.

For example:

4. Conversion of the secondary amine functionality to a tertiary amine or tetraalkyl quaternary ammonium salt.

For preparation of tertiary amines or tetraalkyl ammonium salts, michellamine A or B is reacted with one or two equivalents of alkyl halide (RX, where X = Cl, Br or I and R is an C₁-C₆ aliphatic radical) in anhydrous aprotic solvent. Alternatively, michellamine A or B is reacted with an aldehyde and the resulting product reduced with

NaBH₄.

For example:

5. Substitution of one or more of the hydrogen substituents on the aryl systems (C-7, C-1', C-3', C-7') by halogen, nitro, araino, hydroxyl, thiol, or cyano groups.

For preparation of bromine substituted derivatives, michellamine A or B is reacted with Br₂ in H₂O. For preparation of other substituted derivatives, michellamine A or B is treated with HNO₃/HOAc to provide nitro-substituted (-NO₂) derivatives. In turn, the nitro derivative can be reduced to the amino derivative. The amino-derivative is the point of origin of the chloro, iodo, cyano, thiol and hydroxyl substitution via well known and practiced diazonium substitution reactions.

For example:

EXAMPLE 5. Antiviral Activity of the Michellamines

A battery of interrelated assays on individual wells from 96-well microtiter plates were performed to show antiviral activity. Measurements of cellular viability, in the presence and absence of the compounds in uninfected and virus-infected cells, by an adaptation of the procedure set forth in Weislow, O., et al. J. Natl. Cancer Inst. 81: 577- 586, 1989, as well as by an adaptation of a method using the fluorescent probe 2'-7'-biscarboxyethyl-5(6)- carboxyfluorescein acetoxymethyl ester (BCECF) as set forth in Rink, T.J., et al. J. Cell Biol. 95: 189-196, 1982 were performed and as described herein below. BCECF is a nonfluorescent molecule which readily enters viable cells where it is hydrolyzed by cellular esterases to a fluorescent molecule. Total cellular DNA content was measured with the dye, 2-diamidino-phenylindole (DAPI), which fluoresces when intercalated at A-T specific sites in chromatin, according to the procedure set forth in McCaffrey, T.A., et al., In Vitro Cell. Develop. Biol. 24: 247-252, 1988. These dyes are used in combination with Particle Concentration Fluorescent Immunoassay technology (PCFIA), specifically the Screen Machine™ available from Baxter Healthcare Corporation (Mundelein, IL). The Screen Machine is a semiautomated fluorescent plate reader capable of adding reagents and/or wash buffers to filter-bottomed, 96-well plates with the subsequent evacuation of fluid and concentration of fluorescently-stained cells on the cellulose acetate filter. Fluorescence is detected via epifluorescence.

Also concurrent with the above, confirmatory assays of p24 antigen production, reverse transcriptase activity and synthesis of infectious virions were performed. These and other details of our procedures and results are described in further detail as follows.

Cells and virus. The human lymphocytic target cell lines, CEM-SS and MT-2, used in the antiviral assays were maintained in RPMI 1640 medium (Gibco, Grand Island, NY) without phenol red and supplemented with 5% fetal bovine serum (FBS) (Gibco), 2 mM L-glutamine and 50 μg/ml gentamicin (Gibco) (complete medium). Exponentially-growing CEM-SS or MT-2 cells were pelleted and resuspended at a concentration of 2.0 x 10⁵ cells/ml in complete medium. For the HIV-1 studies, the Haitian variant of HIV, HTLV-III_RF (3.54 x 10⁶ syncytium-forming units/ml, was used. For the HIV-2 studies, the NIH-DZ strain (2.8xl0⁵ syncytium-forming units/ml) was used. Frozen virus stock solutions were thawed immediately before use and resuspended in complete medium to yield 1.2 x 10⁵ SFU/ml.

Reagents. The tetrazolium reagent, XTT, was obtained from the Drug Synthesis and Chemistry Branch, Developmental Therapeutics Program, Division of Cancer Treatment, National Cancer Institute. Biscarboxyethyl-5(6)-carboxy- fluorescein. acetoxymethyl ester (BCECF) was purchased from Molecular Probes, Inc. (Eugene, OR) and dissolved immediately before use in DMSO (1 mg/ml). A working solution of 2 μg/ml was prepared in Dulbecco's phosphate-buffered saline (PBS) (Gibco). 4',6-diamidino-2-phenylindole (DAPI) was purchased from Sigma Chemical Co. (St. Louis, MO). Stock solutions of DAPI were prepared at 100 μg/ml in distilled water by sonication, passed through a 0.45 μm filter and stored at -20°C. Working solutions of DAPI were prepared at 10μg/ml in PBS containing 0.5% nonidet P-40 (NP-40) (Sigma). XTT was prepared at a concentration of 1 mg/ml in serum-free RPMI 1640. Phenazine methosulfate (PMS) (Sigma) was prepared at 0.153 mg/ml in PBS and stored at -20°C. Immediately before use, XTT was dissolved at 37ºC and PMS was added to yield a final concentration of 20 μM.

Protocol for Definitive Anti-HIV Evaluations. The appropriate amounts of the pure compounds for anti-HIV evaluations were dissolved in 100% dimethylsulfoxide (DMSO) then diluted in complete medium to the desired initial concentration (and with final DMSO content not exceeding 1%). Then, all serial dilutions of the michellamines A, B and C, reagent additions and plate-to-plate transfers were carried out using an automated Biomek 1000 Workstation (Beckman Instruments, Palo Alto, CA). Each compound was diluted initially in complete medium and added to a single column of a 96-well microtiter plate (dilution plate). The Biomek was used to perform eight serial dilutions of each drug and to transfer a 100 μl aliquot of each dilution to the test plate. Uninfected CEM-SS or MT-2 cells were plated at a density of 1 x 10⁴ cells in 50 μl of complete medium. Diluted HIV-1 or HIV-2 virus was then added to appropriate wells in a volume of 50 μl to yield a multiplicity of infection of 0.6. Appropriate cell, virus and drug controls were used with the final volume in each well being 200 μl. Uninfected, untreated cell controls and untreated virus infected cell controls were placed on both sides of the 96-well test plates; drug blanks were placed along the top and bottom of the plates. Cells that received test compounds were included in quadruplicate, virus-infected wells and duplicate, uninfected wells. Plates were incubated at 37°C in an atmosphere containing 5% CO₂ for 6 days. Subsequently, aliquots of cell-free supernatant were removed from each well using the Biomek, and analyzed for reverse transcriptase activity, p24 antigen production and synthesis of infectious virions (see further below). A 25 μl sample of .002% (w/v) Fluoricon reference particles (590/620 nm) (Baxter Healthcare Corp.) was added to each well of the test plate to be used as an internal standard for fluorescence assays. The Biomek was used to disperse evenly the contents of each well of the test plate and transfer 50 μl aliquots to each of two new microtiter plates. These plates subsequently were used to measure either cellular viability using BCECF or total DNA content using DAPI.

XTT Assay. As an estimate of cellular viability, the metabolic reduction of the tetrazolium salt, XTT, to the soluble, colored formazan was carried out by adding 50 μl of the XTT/PMS solution to each well of the original test plate and incubating for 4 hrs at 37°C. After incubation the plates were covered with adhesive plate sealers (Dynatech, Alexandria, VA), shaken and optical densities determined using a V-max photometer (Molecular Devices, Inc., Menlo Park, CA) at a test wavelength of 450 nm.

BCECF Assay. Cellular viability also was measured using BCECF. Freshly prepared BCECF solution (25 μl) was added to each well of the microtiter plate, and the plates incubated at 37"C for 30 min. Subsequently, 25 μl of a 2% solution of paraformaldehyde was added to each well and incubated a further 30 min to inactivate the virus. The contents of each well were mixed and a 75 μl aliquot was then transferred to a filter-bottomed, 96-well plate (Baxter Healthcare Corp.). The plate was placed in the Screen Machine programmed to execute the following protocol: (1) add 20 μl of 0.25% w/v suspension of 3.2 μm polystyrene beads (Baxter Healthcare Corp.) in PBS as a filtration support matrix; (2) filter away the liquid phase using a vacuum pressure of 15 mm Hg for l£ min; (3) wash the cell-bead cake in each well with PBS using a vacuum pressure of 20 mm Hg for 1 min; (4) read fluorescence of each well (signal channel = excitation at 485 nm, emission at 535 nm and reference channel = excitation at 590 nm, emission at 620 nm).

DAPI Assay. Total DNA content of each well was determined by the following modifications to the method described by McCaffrey [McCaffrey, T.A., et al. In Vitro Cell. Develop. Biol. 24: 247-252, 1988]. The contents of each well were fixed by adding 25 μl of a 2% paraformaldehyde solution and incubating the plate at 37 °C for 30 min. 25 μl of the DAPI/NP-40 solution was added to each well and incubated for 2 hrs. The contents of each well were mixed and a 75 μl aliquot was transferred to a filter-bottomed 96-well plate (Baxter Healthcare Corp.). The DAPI plate was placed in the Screen Machine and processed by the same protocol as the BCECF plate above with the signal channel set at an excitation of 400 nm and an emission of 450 nm.

p24 Assay. The production of the HIV-1 internal core p24 antigen was measured using a p24 antigen-capture assay (Coulter Immunology, Hialeah, FL). Supernatants from test plates were diluted 1:100 in 10% triton X-100 and stored frozen at -20ºC until needed. Two hundred microliter aliquots of triton X-treated samples were added to microtiter wells previously coated with a murine monoclonal anti-HIV-1 p24 antigen. The plate was sealed and incubated at 37°C for 1 hr. Plate washings were carried out using an automated Denley Wellwash 4 (Coulter Immunology) plate washer. After washing and blotting dry the plate, 200 μl of a biotinylated human monoclonal anti-HIV-1 p24 was added to appropriate wells, and the plates reincubated for 1 hr at 37'C. After additional washing, 200 μl of a streptavidin-horseradish peroxidase solution was added and the plate incubated for 30 min at 37*C. A tetramethylbenzene solution was added to each well and incubated at room temperature for 30 min. Following incubation, an acidic stopping reagent was added to each well and the absorbance read at 450 nm within 30 min using a Vmax photometer (Molecular Devices). The concentration of p24 was determined by comparison with a standard curve of known p24 concentrations.

Svncvtium Assay. The synσytium assay described by Nara [Nara, P.L., et al., AIDS Res. Hum. Retroviruses 3: 283-302, 1987] was used for quantitation of infectious virus. Supernatants from test plates were examined in CEM-SS cell monolayers at multiple dilutions to obtain countable numbers syncytia (50-200 per well) in 2-4 days.

Reverse Transcriptase Assay. A 30 μl aliquot of supernatant was added to 30 μl of a virus disruption buffer containing 50 mM Tris pH 7.8, 0.15 mg/ml dithiothreitol (DTT) and 0.1% triton X-100. A 10 μl sample of lysed virus was added to 30 μl of a cocktail containing 2 μl of 1 M Tris, pH 7.8, 1 μl of 3 M KCl, 5 μl of 3 mg/ml DTT, 5 μl of 0.1 M magnesium acetate, 10 μl of Poly(rA)●p(dT)₁₀ (2 units/ml) (Pharmacia, Piscataway, NJ), 6.5 μl of distilled H₂O, 0.5 μl of 10% Triton X-100 and 10 μl of [³H]dTTP (16.56 Ci/mmol) (Amersham Corp., Arlington Heights, IL). Samples were incubated for 30 min at 37"C, harvested onto DE81 ion exchange paper and allowed to absorb for 15 min. Sample pads first were rinsed six times with 5% Na₂HPO₄, then twice with distilled H₂O. Pads were dried and counted in a liquid scintillation counter. Samples were counted in triplicate.

Linearity of Assay Endpoint to Cell Number. Exponentially-growing CEM-SS cells were harvested, washed and plated in 96-well microtiter wells at varying cell concentrations. Following the cell inoculation, the cells were treated with either XTT, BCECF or DAPI according to the above protocols. The fluorescence assays, using BCECF and DAPI showed excellent linearity over a wide range of cell concentrations. Reproducible results could be obtained from both assays with cell numbers below 1000 cells/assay. The colorimetric XTT assay also showed good linearity but with a higher detection limit of 5,000-10,000 cells/assay.

Antiviral Aetivity of the Michellamines Figures 2 and 3 illustrate the antiviral activity of michellamine A, as the free base or the HBr salt, respectively. Figures 4 and 5 illustrate the antiviral activity of michellamine B, as the free base or the HBr salt, respectively. Both compounds gave very similar activity profiles.

Figs. 2A and 2C, 3A and 3C, 4A and 4C, and 5A and 5C describe the relative numbers of viable human CEM-SS lymphoblastoid target cells, either uninfected (o) or infected (●) with the HIV-1 virus, remaining in the culture wells 6 days after introduction of a range of concentrations of michellamines in the form of their free bases or their HBr salts. The results are represented as the percent of the appropriate uninfected, non-drug treated controls. At michellamine concentrations between approximately 20 to 200 μM, both the BCECF and the XTT viability assays showed essentially complete protection of the target cells from the killing effects of the virus. There was little or no direct cytotoxicity of the michellamines to the target cells with drug concentrations below approximately 100 μM. The results of the DNA assay (Figs. 2B, 3B, 4B and 5B) were consistent with the viability assays; i.e., provided further indication of the antiviral activity of the michellamines; the DNA measurements as expected, paralleled the cell numbers present.

Figures 2D, 3D, 4D and 5D show indices of viral replication in cultures of human CEM-SS lymphoblastoid target cells infected with HIV-1 and assayed 6 days after introduction of various concentrations of michellamines in the form of their free bases or HBr salts. The results are represented as the percent of the appropriate HIV-infected, non-drug treated controls. At michellamine concentrations within the same range giving essentially complete cytoprotection (see above), there was a dramatic, essentially complete inhibition of p24 viral core antigen production (▲) and viral reverse transcriptase activity (■), which are indicators of viral replication; there was a similarly complete inhibition of SFU, further indicating a loss of infectious virus.

In vitro cytoprotective effects such as the above are known to predict for antiviral activity in humans. For example, AZT similarly was selected initially for evaluation in human patients on the basis of its in vitro cytoprotective effects against the AIDS virus in cultured human lymphoblastoid cell lines [Yarchoan, R., et al. Lancet 1; 575-580, 1986].

Figure 6 describes the relative numbers of viable human lymphoblastoid MT-2 cells, either uninfected (o) or infected with the HIV-2 virus (●), remaining in the culture wells 6 days after introduction of a range of concentrations of michellamine A in the form of its free base (Fig. 6A) or in the form of its HBr salt (Fig. 6B). Figure 7 describes the relative numbers of viable human lymphoblastoid MT-2 cells, either uninfected (o) or infected with HIV-2 (●), remaining in the culture wells 6 days after introduction of a range of concentrations of michellamine B in the form of its free base (Fig. 6A) or its HBr salt (Fig. 6B). The results are represented both in figure 6 and in figure 7 as the percent of the appropriate controls. Both michellamines A and B, either as their free bases or as their HBr salts, showed antiviral effects (Figures 6, 7) against HIV-2. However, michellamine B consistently was more potent than michellamine A against HIV-2. With concentrations of michellamine B typically between 30-100 μM, essentially complete protection was obtained against the killing effects of HIV-2 upon MT-2 cells. In contrast, with concentrations of michellamine A as high as 250 μM there was only partial protection (20-40%) of the MT-2 cells against HIV-2.

As described above the michellamines inhibit at least two types of HIV retrovirus. As one skilled in the art will appreciate, the michellamines and compositions thereof will likely inhibit other retroviruses and other pathogenic viruses.

EXAMPLE 6. Pharmaceutical Compositions

The compounds of the present invention may be made into pharmaceutical compositions by combination with appropriate, pharmaceutically acceptable carriers or diluents, and may be formulated into preparations in solid, semi-solid, liquid or gaseous forms such as tablets, capsules, powders, granules, ointments, solutions, suppositories, injections, inhalants, and aerosols in the usual ways for their respective route of administration.

The compounds can be used singularly alone, in combination with each other, or can be used in combination with other antiviral agents. When patients infected with HIV-1 and/or HIV-2 are being treated, at least one compound of the present invention can be co-administered with AZT. The following methods and excipients are merely exemplary and are in no way limiting.

In pharmaceutical dosage forms, the compounds of the present invention may be used in the form of their pharmaceutically acceptable salts, and also may be used alone or in appropriate association, as well as in combination with other pharmaceutically active compounds.

In the case of oral preparations, the compounds of the present invention may be used alone or in combination with appropriate additives to make tablets, powders, granules or capsules, e.g., with conventional additives such as lactose, mannitol, corn starch or potato starch; with binders such as crystalline cellulose, cellulose derivatives, acacia, corn starch or gelatins; with disintegrators such as corn starch, potato starch or sodium carboxymethylcellulose; with lubricants such as talc or magnesium stearate; and if desired, with diluents, buffering agents, moistening agents, preservatives and flavoring agents.

The compounds of the present invention may be formulated into preparations for injections by dissolving, suspending or emulsifying them in an aqueous or nonaqueous solvent, such as vegetable or other similar oils, synthetic aliphatic acid glycerides, esters of higher aliphatic acids or propylene glycol; and if desired, with conventional additives such as solubilizers, isotonic agents, suspending agents, emulsifying agents, stabilizers and preservatives.

The compounds of the present invention can be utilized in aerosol formulation to be administered via inhalation. The compounds of the present invention can be formulated into pressurized acceptable propellants such as dichlorodifluoromethane, propane, nitrogen and the like.

Furthermore, the compounds of the present invention may be made into suppositories by mixing with a variety of bases such as emulsifying bases or water-soluble bases. The compounds of the present invention can be administered rectally via a suppository. The suppository can include vehicles such as cocoa butter, carbowaxes and polyethylene glycols, which melt at body temperature, yet are solidified at room temperature.

Unit dosage forms for oral or rectal administration such as syrups, elixirs, and suspensions may be provided wherein each dosage unit, e.g., teaspoonful, tablespoonful, tablet or suppository contains a predetermined amount of the composition containing compounds of the present invention; similarly, unit dosage forms for injection or intravenous administration may comprise a michellamine composition as a solution in sterile water, normal saline or other pharmaceutically acceptably carrier.

The term "unit dosage form" as used herein refers to physically discrete units suitable as unitary dosages for human and animal subjects, each unit containing a predetermined quantity of compounds of the present invention calculated in an amount sufficient to produce the desired effect in association with a pharmaceutically acceptable, diluent, carrier or vehicle. The specifications for the novel unit dosage forms of the present invention depend on the particular compound employed and the effect to be achieved, and the pharmacodynamics associated with each compound in the host.

The pharmaceutically acceptable excipients, for example vehicles, adjuvants, carriers or diluents, are readily available to the public.

One skilled in the art can determine easily the appropriate method of administration for the exact formulation of the composition being used. Any necessary adjustments in dose can be made readily to meet the nature or severity of the infection and adjusted accordingly by the skilled practitioner.

EXAMPLE 7. Use of Compositions Containing Compounds of the Present Invention for Treating Viral Infections

The present invention relates further to a method of treating viral infections comprising the administration of an antiviral effective amount of the composition of the present invention. .Antiviral effective amount is defined as that amount of compound required to be administered to an individual patient to achieve an antiviral effective blood and/or tissue level to inhibit the virus. The antiviral effective blood level might be chosen, for example, to inhibit a virus in a screening assay. An example of such an amount would be 20-200μM, e.g., see from Figures 2-7. Alternatively, the antiviral effective blood level can also be defined as that concentration which inhibits markers (e.g., p24) of the virus in the patient's blood, or which renders the patient asymptomatic to the particular viral infection. Since a fixed antiviral effective blood level is used as the preferred endpoint for dosing, the actual dose and schedule for drug administration for each patient will vary depending upon interindividual differences in pharmacokinetics, drug disposition and metabolism. Moreover, the dose may vary when the compounds are used prophylactically or when used in combination with other drugs.

Such dosage amounts can be readily ascertained without undue burden and experimentation by those skilled in the art.

As an example of an antiviral effective amount, the dosage for humans can range from about between 0.01 mg/kg body weight to 200 mg/kg body weight.

While the foregoing invention has been described in some detail for purposes of clarity and understanding, it will be appreciated by one skilled in the art from a reading of this disclosure that various changes in form and detail can be made without departing from the true scope of the invention.

Claims

WHAT IS CLAIMED;

1. A compound having the formula:

or

in substantially pure form; or a pharmacologically acceptable salt thereof.

2. A compound having the formula:

wherein R¹ and R⁶ are the same or different and are each C₁-C₆ alkyl, R¹¹CO-, or R¹¹SO₂- wherein R¹¹ is C₁-C₆ alkyl or aryl;

R², R³, R⁴, R⁷, R⁸ and R⁹ are the same or different and are each C₁-C₆ alkyl, R¹¹CO-, R¹¹SO₂- wherein R¹¹ is defined above;

R⁵ and R¹⁰ are C₂-C₆ alkyl

wherein R₁₂ is C₁-C₆ alkyl or R¹³CO- or R¹³SO₂-, wherein R¹³ is C₁-C₆ alkyl or aryl;

and wherein the ring H position at 1', 3', 7', 4 and 7 can be substituted with a halogen, nitro, amino, hydroxyl, thiol or cyano group; or a pharmacologically acceptable salt thereof;

3. A method of isolating a compound having the formula:

or

from .Ancistrocladus abbreviatus which comprises the steps of:

(a) extracting dried plant material with an organic solvent to obtain a crude extract;

(b) acid-base partitioning said crude extract to obtain a crude organic base fraction;

(c) subjecting said crude organic base fraction to centrifugal partition chromatography; and

(d) isolating said michellamines with an amino-bonded phase HPLC column.

4. A method of interconverting michellamines A or B into a mixture of michellamines A, B and C, which comprises:

(a) dissolving michellamines A or B in an organic solvent; and

(b) reacting said michellamines A or B with a base.

5. The method according to Claim 4, wherein said base is sodium hydroxide.

6. The method according to Claim 4, wherein said organic solvent is methanol.

7. An antiviral composition which comprises an antiviral effective amount of at least one compound according to Claim 1; and a pharmacologically acceptable carrier.

8. An antiviral composition which comprises an antiviral effective amount of at least one compound according to Claim 2; and a pharmaceutically acceptable carrier.

9. The composition according to Claim 7, further comprising an antiviral effective amount of AZT or other known effective antiviral agent.

10. The composition according to Claim 8, further comprising an antiviral effective amount of AZT or other known effective antiviral agent.

11. Use of a compound according to claim 1 for the treatment of a viral infection wherein an antiviral effective amount of the compound is administered to a patient in need thereof.

12. The method according to Claim 11, which further comprises co-administering an antiviral effective amount of AZT.

13. The method according to Claim 11, wherein said virus is a retrovirus.

14. The method according to Claim 13, wherein said retrovirus is a human immunodeficiency virus.

15. The method of Claim 14, wherein said human immunodeficiency virus is selected from the group consisting of HIV-1 and HIV-2.

16. Use of a compound according to claim 2 for the treatment of a viral infection wherein an antirival effective amount of the compound is administered to a patient in need thereof.

17. Use according to Claim 16, wherein an antiviral effective amount of AZT is co-administered.

18. Use according to Claim 16, wherein said virus is a retrovirus.

19. Use according to Claim 18, wherein said retrovirus is a human immunodeficiency virus.

20. Use according to Claim 19, wherein said human immunodeficiency virus is selected from the group consisting of HIV-1 and HIV-2.