JP2006282577A - Novel photosensitizer for photodynamic therapy of cancer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel compound and a medicine for photodynamic therapy of a cancer containing the same as a photosensitizer. <P>SOLUTION: The novel compound is methyl 5-acetamide-4-oxo-5-hexenoate represented by formula (IX) synthesized by adding methyl 5-azide-4-oxo-hexanoate and NaReO<SB>4</SB>and CF<SB>3</SB>SO<SB>2</SB>H as catalysts into a mixed solution of acetic anhydride and carbon tetrachloride and refluxing the mixture. The photosensitizer comprises the compound. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel compound, a process for producing the same, and a medicament for cancer photodynamic therapy comprising the compound or a pharmaceutically acceptable salt thereof as a photosensitizer.

  There are various methods for treating cancer, such as surgery, radiation therapy, and chemotherapy, and a preferred method is selected according to the nature of the cancer to be treated, the site in the body, and the like. However, many of the methods such as radiation therapy and chemotherapy are known to have severe side effects, mainly because these methods have relatively indiscriminate cytotoxicity. Therefore, photodynamic therapy (hereinafter referred to as PDT), which is a treatment method that is more selective for diseased tissue, greatly reduces the above disadvantages compared to many other cancer treatment methods. It can be done.

  The PDT principle of Gunn is that the combination of visible light and photosensitizer is both harmless per se, but if both and oxygen are present at the same time, the photosensitizer is photoexcited to a photoexcited triplet state. Based on the phenomenon of producing deadly cytotoxic substances that inactivate cancer cells. And this method of applying photosensitizer, oxygen and light simultaneously is that the diseased tissue selectively takes up the photosensitizer compared to normal tissue (about twice), and the light irradiation is the diseased tissue Due to the dual selectivity to cancer tissue obtained by limiting the activation of photosensitizers in normal tissues exclusively, only the diseased tissue is exposed to cytotoxic substances, Allows selective destruction of tumors while keeping normal tissue intact.

A photosensitizer is a compound that absorbs light of a specific wavelength and converts it into useful energy. Particularly in PDT, photosensitizers are characterized by being selectively accumulated in diseased tissues and producing cytotoxic substances. The mechanism of action of photosensitizers in PDT has been elucidated in detail. By photoirradiation, the photosensitizer is first excited from the ground state (S0) to the first excited state (S1), and further converted to the triplet state (T1) via an intermolecular cross-link. The long-lasting triplet state also allows interaction of the excited photosensitizer with surrounding molecules and generation of cytotoxic species between the PDT. Specifically, the excited photosensitizer ultimately leads to tumor cell destruction in PDT via either of the following two types of reactions (Non-patent Document 1):
1) Generation of highly reactive free radicals and radical ions by removal of hydrogen atoms or electron transfer with either biological solvents or other photosensitizers. This reacts with the oxygen molecules to produce reactive oxygen species such as superoxide anions, causing biological damage by oxygen to the cells; and 2) energy transfer between the ground state oxygen molecules and the first Singlet oxygen which is oxygen in an excited state is generated. This highly reactive zwitterionic species reacts with many biological substrates to cause oxidative damage, leading to cell death.

｛式中、R₁とR₂は、‐CH(OH)CH₃又は‐CH=CH₂であり、そして、ｎは、０〜６の整数である。｝
により表される、フォトフリン（登録商標）などのヘマトポルフィリン誘導体である。ヘマトポルフィリンは、エーテル結合を持つ２０種類以上の混合物からなり、ヘム色素と同様、光増感剤において重要と考えられる以下の式（II）：

により表されるポルフィリン環を有している。ポルフィリン及びヘムはどちらもすべてのエネルギー産生細胞において合成され、ヘムタンパク質の補欠分子団に含まれる。後述する他の光増感剤である５−アミノレブリン酸（ALA）を介して合成されるヘムは、呼吸によって酸素を取り込んでラジカルを形成し、これによってDNAが切断されて細胞死をもたらすと考えられる。しかしながら、ヘマトポルフィリン誘導体には、可視領域の中でも比較的波長の短いところに極大吸収があり、組織透過性の良い長波長領域には吸収がないこと、及び腫瘍への選択性が低いという2つの欠点があり、その効果は限定的なものである（非特許文献２）。 Many of conventionally used photosensitizers were synthesized by treating hematoporphyrin with an acid, which has the following formula (I):

{Wherein R ₁ and R ₂ are —CH (OH) CH ₃ or —CH═CH ₂ , and n is an integer of 0-6. }
A hematoporphyrin derivative such as Photofurin (registered trademark) represented by: Hematoporphyrin is a mixture of 20 or more types having an ether bond, and, like heme dyes, the following formula (II) considered to be important in a photosensitizer:

It has the porphyrin ring represented by these. Both porphyrins and heme are synthesized in all energy producing cells and are included in the prosthetic group of heme proteins. Heme synthesized via 5-aminolevulinic acid (ALA), another photosensitizer described below, is thought to take oxygen and form radicals by respiration, thereby cleaving DNA and causing cell death. It is done. However, hematoporphyrin derivatives have a maximum absorption at a relatively short wavelength in the visible region, no absorption in a long wavelength region with good tissue permeability, and low selectivity for tumors. There are drawbacks and the effects are limited (Non-Patent Document 2).

により表されるメチレンブルーがある。しかしながら、この化合物は低毒性であるという利点を有する一方、細胞内酵素によって普遍的に還元されて光増感剤としての活性を失ってしまうことから、そのインビボにおける光増感剤としての使用は限定的なものである（非特許文献１）。 In addition to the hematoporphyrin derivative, photosensitizers recently used in clinical practice are widely used as colorants in biological assays and have the following formula (III):

There is methylene blue represented by However, while this compound has the advantage of low toxicity, since it is universally reduced by intracellular enzymes and loses its activity as a photosensitizer, its use as a photosensitizer in vivo is not possible. Limited (Non-Patent Document 1).

により表される５−アセタミド−４−オキソ−５−ヘキセン酸を抗生物質のスクリーニングにおいて見出した。そして、ストレプトミセス属放線菌が生産するこの化合物が、ジャイレース活性の阻害を介して染色体分配を阻害する抗菌活性を有することを明らかにした（非特許文献３）。さらに該化合物は、以下の式（V）：

により表される抗癌抗生物質プリモカルシン（非特許文献４）の公知の類縁体であり（非特許文献５）且つポルフィリンの前駆体であって従来の光増感剤の一つである、以下の式（VI）：

により表される、ALAと構造が類似していることから、ポルフィリン合成系に作用して細胞の光感受性を増大させることが期待された。しかしながら、光増感剤としてのALAは、低分子であり、極性を有することから、多くの皮膚症状に対する局所的PDT、表在性基底細胞癌などにも使用可能であると考えられる一方、局所剤として使用した場合、あまり皮膚の奥深くまでは浸透しないという問題も有する（非特許文献１）。 In the previous study we named the following formula (IV):

The 5-acetamido-4-oxo-5-hexenoic acid represented by was found in antibiotic screening. And it was clarified that this compound produced by Streptomyces genus actinomycetes has antibacterial activity that inhibits chromosome partitioning through inhibition of gyrase activity (Non-patent Document 3). Further, the compound has the following formula (V):

Is a known analog of the anticancer antibiotic primocalcin (Non-Patent Document 4) represented by the formula (Non-Patent Document 5) and a precursor of porphyrin and one of the conventional photosensitizers, Formula (VI):

Since the structure is similar to that of ALA, it was expected to increase the photosensitivity of cells by acting on the porphyrin synthesis system. However, since ALA as a photosensitizer is a small molecule and has polarity, it can be used for local PDT, superficial basal cell carcinoma, etc. When used as an agent, it also has a problem that it does not penetrate deeply into the skin (Non-Patent Document 1).

  Therefore, development of a novel photosensitizer that overcomes these drawbacks is required.

により表されるそのエチルエステル（５−アセタミド−４−オキソ−５−ヘキセン酸エチルエステル）は、従来技術であるプリモカルシン合成反応の中間体としてすでに合成された公知の化合物である。その方法は、以下の式（VIII）：

により表される化合物を出発物質として使用し、いくつかの反応を経て５−アセタミド−４−オキソ−５−ヘキセン酸エチルエステルを中間体として得ることを含むものであった。得られた上記エチルエステルをアンモニア処理して得られるのが、プリモカルシンである（非特許文献５）。 Among the analogs of 5-acetamido-4-oxo-5-hexenoic acid, a compound known as described above, the following formula (VII):

The ethyl ester represented by the formula (5-acetamido-4-oxo-5-hexenoic acid ethyl ester) is a known compound that has already been synthesized as an intermediate of the prior art primocalcin synthesis reaction. The method comprises the following formula (VIII):

Using as a starting material and through several reactions to obtain 5-acetamido-4-oxo-5-hexenoic acid ethyl ester as an intermediate. Primocalcin is obtained by treating the obtained ethyl ester with ammonia (Non-patent Document 5).

  The compound of the present invention, which is a methyl ester corresponding to the ethyl ester, 5-acetamido-4-oxo-5-hexenoic acid methyl ester is a novel compound, and is also described in Non-Patent Document 5 describing the ethyl ester. Therefore, the synthesis method of the methyl ester is not known. Furthermore, applying the above reaction to the synthesis of 5-acetamido-4-oxo-5-hexenoic acid methyl ester was expected to reduce the selectivity and yield of the reaction. In addition, the description relating to the above method has some unclear points such as not including a synthesis method of the starting material.

Sharman, W., et al., DDT Vol. 4, No. 11 November (1999) 507-517 Ichiro Okura, “Photodynamic Therapy Using Porphyrins” Living Body Polymers, edited by the Society of Polymer Science, p.133-145 Awa Yuuki, Iwai Hakutaka, Nagai Kazuo, Wachi Masaaki, (2002) Isolation of natural product-derived Gyrase inhibitor, Proceedings of the 25th Annual Meeting of the Molecular Biology Society of Japan, p.562 (antibiotic 5-Acetamido- Separation and structure determination of 4-oxo-5-hexanoic acid) II. J. Antibiotics, Ser. A, 15, 77-79 (Anti-cancer antibiotic primocarcin (5-Acetamido-4-oxo-5-hexenoic acid-related compounds) and their properties) Bowman, R. E., Closier, M. D., and Islip P.J. (1965) The Synthesis of primocarcin and analogues. J. Chem. Soc., 470-473. (Synthesis of Primocarcin and its analogs) Carmichael, J., DeGraff, W.G., Gazgar, A.F., Minna, J.D., and Mitchell, J.B.Evaluation of a tetrazolium-based semiautomated colorimetric assay: assessment of chemosensitivity testing.Cancer Res., 47, 936-942, 1987

  An object of the present invention is to provide a novel compound for a photosensitizer or a pharmaceutically acceptable salt thereof in place of a hematoporphyrin derivative, a method for producing the compound, and a medicament for cancer photodynamic therapy containing the compound or salt. Is to provide.

により表される化合物である５‐アセタミド‐４‐オキソ‐５‐ヘキセン酸メチルエステル、又は薬学的に許容可能なその塩が提供される。 According to the invention, the following formula (IX):

5-Acetamide-4-oxo-5-hexenoic acid methyl ester, or a pharmaceutically acceptable salt thereof, is provided as a compound represented by:

により表される５−アジド−４−オキソ−ヘキサン酸メチルエステル並びに触媒としてのNaReO₄及びCF₃SO₂Hを、無水酢酸及び四塩化炭素の混合溶液中に加えて還流すること；
を含む、前記方法が提供される。 According to the present invention, there is provided a process for producing the novel compound 5-acetamido-4-oxo-5-hexenoic acid methyl ester, comprising the following steps:
The following formula (X):

Adding 5-azido-4-oxo-hexanoic acid methyl ester represented by the formula: NaReO ₄ and CF ₃ SO ₂ H as catalysts in a mixed solution of acetic anhydride and carbon tetrachloride;
Wherein said method is provided.

  Further, according to the present invention, there is provided a medicament for cancer photodynamic therapy comprising 5-acetamido-4-oxo-5-hexenoic acid methyl ester or a pharmaceutically acceptable salt thereof as a photosensitizer.

  In the process of synthesizing 5-acetamido-4-oxo-5-hexenoic acid found in antibiotic screening, the present inventors synthesized a novel compound 5-acetamido-4-oxo-5-hexenoic acid methyl ester. succeeded in.

  The synthesized 5-acetamido-4-oxo-5-hexenoic acid methyl ester showed a higher photosensitivity increasing effect than the conventional photosensitizer ALA.

Explanation of Terms In this specification, the terms “cancer photodynamic therapy” and “PDT” are used interchangeably, and both of them are used to administer a photosensitizer to a cancer patient and perform laser light irradiation to treat the tumor. It means a method of necrosis (Non-Patent Document 1).

  As used herein, the term “photosensitizer” means a compound that absorbs light of a specific wavelength and converts it into useful energy.

により表されるアジ化ケトン（５−アジド−４−オキソ−ヘキサン酸メチルエステル）を合成する。 The present inventors have succeeded in synthesizing the above novel compound 5-acetamido-4-oxo-5-hexenoic acid methyl ester in the process of synthesizing 5-acetamido-4-oxo-5-hexenoic acid (see FIG. 1). ). In that method, 4-pentynylcarboxylic acid is first used as a starting material, and the following formula (X), which is an intermediate of synthesis by a conventional method:

The azide ketone represented by the formula (5-azido-4-oxo-hexanoic acid methyl ester) is synthesized.

により表される５−アミノ−４−オキソ−５−ヘキセン酸メチルエステルを合成し、これからさらに以下の式（IV）：

により表されるカルボン酸アミド（５−アセタミド−４−オキソ−５−ヘキセン酸）を得ようと試みた。しかし、合成された５−アミノ−４−オキソ−５−ヘキセン酸メチルエステルは非常に不安定であり、該合成反応の中間体として使用することは不可能であった。 Initially, as a next step, the inventors added sodium ethoxide in ethanol to the azide ketone of the above formula (X) to convert the azide group of the azide ketone to an amino group, and 5th and 6th positions. By forming a double bond between the carbons of the following formula (XI):

5-amino-4-oxo-5-hexenoic acid methyl ester represented by the following formula (IV):

An attempt was made to obtain a carboxylic acid amide represented by the formula (5-acetamido-4-oxo-5-hexenoic acid). However, the synthesized 5-amino-4-oxo-5-hexenoic acid methyl ester was very unstable and could not be used as an intermediate in the synthesis reaction.

  Therefore, the present inventors carried out reduction and acetylation simultaneously on the azide group in the azide ketone of the above formula (X), whereby the amide (5-acetamido- 4-oxo-5-hexenoic acid methyl ester) was devised, and the resulting amide was used to successfully synthesize a carboxylic acid amide of formula (IV) (see FIG. 1).

  As described above, the novel compound 5-acetamido-4-oxo-5-hexenoic acid methyl ester of the present invention was obtained as a synthetic intermediate of 5-acetamido-4-oxo-5-hexenoic acid. As already mentioned, it was expected that it would not be suitable to synthesize it in the same way as the corresponding ethyl ester by the prior art. On the other hand, the method of the present invention is completely different from the above-described prior art in starting materials and reaction steps, and the target methyl ester can be synthesized in a high yield by an easy reaction. It was. In addition, various α-carbonyl compounds are synthesized through further hydrogenation of the 6-position carbon of araremycin (5-acetamido-4-oxo-5-hexenoic acid) synthesized from the above methyl ester. The above steps can be widely applied in the production process of α-carbonyl compounds.

According to a preferred embodiment of the present invention, the solvent used in the above step together with acetic anhydride which is a solvent and a source of acetyl groups is a halogenated solvent, preferably chloroform, methylene chloride or carbon tetrachloride. More preferably, carbon tetrachloride is used. In the method of the present invention, methyl 5-azido-4-oxo-hexanoate was obtained by using NaReO ₄ as a catalyst instead of NaOEt in EtOH usually used for the conversion reaction from azide ketone to amide. Succeeded in synthesizing 5-acetamido-4-oxo-5-hexenoic acid methyl ester from the ester. The amount of NaReO ₄ is 0.005 to 0.03 equivalents, more preferably 0.013 eq.

  In order for the obtained 5-acetamido-4-oxo-5-hexenoic acid methyl ester to have a photosensitivity increasing effect in cells, the acetyl moiety in the acetamide group introduced by the synthesis step described above in an aqueous solution was used. The above synthesis method, which requires the stabilization of the compound and the generation of radicals in the cell by the methylene moiety, can efficiently introduce these moieties that give the compound characteristics as an effective photosensitizer, It is useful for. In addition, in order to be efficiently taken up into cells, it is also necessary to be a fat-soluble compound having a high cell membrane permeability, and the methyl ester of the present invention is also excellent in this respect.

  Furthermore, derivatives thereof including 5-acetamido-4-oxo-5-hexenoic acid can be synthesized from the above methyl ester by a conventional method. The above novel synthesis method of methyl 5-acetamido-4-oxo-5-hexenoate and its derivatives has made it possible to stably supply these new lead compounds for the development of new photosensitizers.

  In addition, experiments using Hela cells revealed that 5-acetamido-4-oxo-5-hexenoic acid methyl ester exhibits superior photosensitivity compared to the conventional photosensitizer ALA. . The effect of photosensitizer on cancer cell viability (photosensitivity) shown by contacting cancer cell with photosensitizer in vitro and irradiating with light (or laser) is the same as photosensitizer It has already been proved that there is a positive correlation between the growth inhibitory effect on solid tumors in mice in vivo (Non-patent Document 2). Therefore, the methyl ester is expected as a lead compound for developing a new photosensitizer. Further, 5-acetamide-4-oxo-5-hexenoic acid (araremycin), which is a structural analog, has antibacterial activity, but the methyl ester of the present invention also exhibits antibacterial activity.

  Unless otherwise noted, the reactants used in the following examples were obtained commercially.

Example 1 Synthesis of 5-acetamido-4-oxo-5-hexenoic acid via 5-acetamido-4-oxo-5-hexenoic acid methyl ester as an intermediate The following steps were performed according to the synthetic scheme shown in FIG. By carrying out the synthesis, 5-acetamido-4-oxo-5-hexenoic acid was synthesized through the use of 5-acetamido-4-oxo-5-hexenoic acid methyl ester as an intermediate (see FIG. 1).
1) Synthesis of lactone (tetrahydro-2-ethylidene-5-furanone represented by the formula (XIII) in FIG. 1)
In a flask containing PDCl ₂ (PhCN) ₂ (54 mg, 0.14 mmol), MeCN (25 mL), Et ₃ N (0.060 mL, 0.43 mmol), and carboxylic acid (represented by the formula (XII) in FIG. 1). 4-pentynylcarboxylic acid) (0.16 g, 14.3 mmol) was added in this order and heated to reflux for 5 hours. The solvent was distilled off under reduced pressure, and the crude product was subjected to silica gel chromatography (silica gel 60 manufactured by Merck & Co., Inc.) to obtain 1.36 g of a lactone of the formula (XIII) (yield 85%): ¹ H NMR δ 1.68 (dt, J = 7.2 Hz, 3H), 2.54-2.70 (m, 2H), 2.76-2.86 (m, 2H), 4.62 (tq, J = 1.5, 7 Hz, 1H)

2) Synthesis of bromoketone (5-bromo-4-oxohexanoic acid methyl ester represented by formula (IVX) in FIG. 1) Lactone (850 mg, 7.58 mmol) of formula (XIII) was dissolved in CCl ₄ (10 mL). After cooling to 0 ° C., a solution of Br ₂ (0.39 mL, 7.57 mmol) in CCl ₄ (2 mL) was added dropwise thereto. After 30 minutes, it was concentrated and a small amount of MeOH (10 mL) and Et ₃ N were added. The mixture was stirred at room temperature for 1 hour and concentrated. The crude product thus synthesized was subjected to silica gel chromatography to obtain 1.20 g of bromoketone of formula (IVX) (yield 71%): ¹ H NMR δ1.77 (d, J = 7 Hz, 3H), 2.49- 2.78 (m, 2H), 2.91 (ddd, J = 18, 7.5, 6Hz, 1H), 3.14 (ddd J = 18, 6.5, 6Hz, 1H), 3.69 (s, 3H), 4.49 (q, J = 7Hz , 1H); ¹³ C NMR δ20.2, 28.4, 33.6, 47.5, 52.0, 172.8, 202.9.

3) Synthesis of azide ketone (5-azido-4-oxo-hexanoic acid methyl ester represented by formula (X)) Bromoketone of formula (IVX) (1.20 g, 5.38 mmol) was dissolved in DMF (5 mL). To this, NaN ₃ (699 mg, 10.8 mmol) was added. After stirring at room temperature for 1 hour, water was added. The product was extracted 3 times with Et ₂ O. The extract was dried over MgSO ₄ and concentrated. The crude product was subjected to silica gel chromatography to obtain 976 mg of azide ketone of formula (X) (yield 98%): ¹ H NMR δ1.41 (d, J = 7 Hz, 3H), 2.56-2.62 (m , 2H), 2.77-2.83 (m, 2H), 3.63 (s, 3H), 3.97 (q, J = 7 Hz, 1H); ¹³ C NMR δ 15.8, 27.6, 33.7, 51.9, 63.2, 172.6, 205.8.

4) Synthesis of amide (5-acetamido-4-oxo-5-hexenoic acid methyl ester represented by formula (IX))
In a mixed solution of Ac ₂ O (0.5 mL) and CCl ₄ (0.5 mL), NaReO ₄ (1 mg, 0.0037 mmol), CF ₃ SO ₃ H
(0.001 mL, 0.011 mmol) and an azide ketone of formula (X) (50 mg, 0.27 mmol) were added and heated to reflux for 10 hours. The solution was concentrated under reduced pressure and the crude product was subjected to silica gel chromatography to obtain 34 mg of the amide of formula (IX) (yield 63%): ¹ H NMR δ2.12 (s, 3H), 2.68 (t , J = 6.5Hz, 2H) 3.11 (t, J = 6.5Hz, 2H), 3.70 (s, 3H), 5.84 (t, J = 1Hz, 1H), 6.93 (d, J = 1Hz, 1H), 7.99 (br s, 1H); ¹³ C NMR δ 24.8, 28.1, 30.8, 52.0, 109.5, 137.7, 169.0, 172.7, 194.9.
5) Synthesis of carboxylic acid amide (5-acetamido-4-oxo-5-hexenoic acid represented by formula (IV)) In a mixed solvent of ice-cooled MeOH (1.1 mL) and H ₂ O (1.1 mL) The amide of formula (IX) (180 mg, 0.904 mmol) and 1N lithium hydroxide (1.2 mL) were added. The solution was stirred for 30 minutes at the same temperature, after which the solution was made weakly acidic by adding 10% tartaric acid. The product was extracted 3 times with ethyl acetate and the extract was dried over MgSO ₄ and concentrated. Finally, the crude product was subjected to silica gel chromatography to obtain 6148 mg of carboxylic acid amide of formula (IV) (yield 88%): ¹ H NMR (in (CD ₃ ) ₂ SO) δ2.02 (s, 3H), 2.46-2.51 (m, 2H), 2.96 (t, J = 6Hz, 2H), 5.79 (s, 1H), 6.46 (s, 1H), 9.10 (br s, 1H), 12.15 (bs s, 1H); ¹³ C NMR (in CD ₃ OD) δ 24.0, 28.9, 32.2, 110.6, 140.1, 172.0, 176.0, 196.6.

Example 2 Increased photosensitivity by 5-aminolevulinic acid and 5-acetamido-4-oxo-5-hexenoic acid methyl ester Human uterine cancer cell Hela cells were seeded in a 35 mm petri dish at 2 × 10 ^{4. -4} M, 10 ^-5 M concentrations of 5-acetamido-4-oxo-5-hexenoic acid methyl ester alone and in the presence of 10 ^-3 M ALA were contacted in the dark for 1 hour before washing. . The cells after this treatment were further divided into a group irradiated with light and a group maintained in the dark (3 cases per group). Light irradiation 500W halogen lamp (Toshiba, 425WN-EH) irradiating light of at least 500nm, the light intensity was 28 J / cm ^2. 24 hours after irradiation, cell viability was determined by the MTT method (Non-patent Document 6) (see FIG. 2). By light irradiation, ^10-4 molar concentrations of 5-acetamido-4-oxo-5-hexenoic acid methyl ester alone after treatment of cell viability decreased by about 30%, about the after irradiation with 10 ^-3 molar Compared to 5-aminolevulinic acid, which shows 90% cell viability, it showed a marked increase in cytotoxicity due to light irradiation. In addition, even when 10-4 molar concentration of 5-acetamido-4-oxo-5-hexenoic acid methyl ester is used in combination with 10-3 molar concentration of 5-aminolevulinic acid, compared with the case where it is placed in the dark by light irradiation. The cell viability was significantly reduced. This confirmed that photosensitivity of 5-acetamido-4-oxo-5-hexenoic acid methyl ester to cells was increased.

FIG. 1 is a scheme showing a method for synthesizing 5-acetamido-4-oxo-5-hexenoic acid via 5-acetamido-4-oxo-5-hexenoic acid methyl ester as an intermediate. FIG. 2 shows the increase in photosensitivity of Hela cells by 5-aminolevulinic acid and 5-acetamido-4-oxo-5-hexenoic acid methyl ester when exposed to light after exposure to the drug and in the dark. 2 is a bar graph showing by comparing cell viability of cells.

Claims (3)

The following formula (IX):

5-Acetamide-4-oxo-5-hexenoic acid methyl ester, or a pharmaceutically acceptable salt thereof, which is a compound represented by: A method of synthesizing 5-acetamido-4-oxo-5-hexenoic acid methyl ester according to claim 1, comprising the following steps:
The following formula (X):

Adding 5-azido-4-oxo-hexanoic acid methyl ester represented by the following formula and NaReO ₄ and CF ₃ SO ₂ H as catalysts in a mixed solution of acetic anhydride and carbon tetrachloride, and refluxing:
Said method.   A medicament for the treatment of cancer photodynamics comprising the 5-acetamido-4-oxo-5-hexenoic acid methyl ester according to claim 1 or a pharmaceutically acceptable salt thereof as a photosensitizer.

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