JPH0788342B2 - 3-Nitro-2,4,6-trihydroxybenzamide and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel 3-nitro-2,4,6-trihydroxybenzamide and a method for producing the same.

[Background of the Invention]

Grangenol contained in the eucalyptus trunk is known to have germination and photosynthesis inhibitory activity. It is also known that when the side chain-alkyl group of Grangenol becomes long, the photosynthesis inhibitory activity becomes large, and conversely when it becomes short, the germination inhibitory activity becomes large. The present inventor previously synthesized a compound in which a nitro group was introduced instead of the formyl group of grangenol, and found that this compound has the same physiological activity as grangenol.

[Problems to be Solved by the Invention]

An object of the present invention is to provide a novel 3-nitro-2,4,6-trihydroxybenzamide having a physiological activity equivalent to or higher than that of the above-mentioned conventional compounds and a method for producing the same.

[Means for Solving the Problems]

 The novel compound of the present invention is represented by the following general formula (I).

(In the formula, R ¹ represents an alkyl group or a cycloalkyl group, and R ² represents a hydrogen atom or a lower alkyl group.) The above compound can be represented by, for example, the following general formula (II): (In the formula, R ² represents a hydrogen atom or a lower alkyl group.) The compound represented by the general formula (II
I): A compound represented by the following formula (IV): R ¹ NCO (IV) (wherein R ¹ represents an alkyl group or a cycloalkyl group) To be done.

Examples of the R ¹ group of the isocyanate R ¹ NCO used in the present invention include methyl, ethyl, n-propyl, n-butyl,
n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-
Examples thereof include tridecyl, n-pentadecyl, n-octadecyl, cyclohexyl and the like.

Next, a method for synthesizing the compound of the present invention will be described.

First, as a nitrating agent for phloroglucinol (II) (R ² = H), 35-40% nitric acid aqueous solution is preferable.

Also, as the reaction solvent, the aqueous nitric acid solution is preferable, but in order to avoid dinitration, a higher yield can be obtained by mixing the following inert organic solvent. The solvent that can be used is dichloromethane, a mixture of dichloromethane and pentane (3: 1
~ 8: 1), dichloroethane and the like.

A reaction temperature of 10 ° C to 30 ° C and a reaction time of 1 day to 3 days are suitable.

Obtained nitro compound (III) and isocyanate (IV)
The reaction with is preferably carried out in a nitrobenzene solvent using aluminum chloride as a catalyst. Reaction temperature is 60-70
It is suitable that the reaction temperature is half a day to one day and one night.

Biological activity test A method as described below for the germination inhibitory activity GI ₅₀ (50% germination inhibitory concentration) and photosynthetic electron transfer inhibitory activity PI ₅₀ (negative value of the 50% photosynthetic electron transport inhibitory concentration) of the compound of the present invention It was measured at.

The activity values of each substance are shown in Table 1.

1) Germination inhibition test (using cress seeds) A petri dish (inner diameter 5 cm) lined with filter paper is used as a container. If the frequency of experiments is high, use disposable plastic Petri dishes. First, the test compound is dissolved in ethyl alcohol at a predetermined concentration. A predetermined amount of alcohol solution is uniformly soaked in a filter paper in a Petri dish, and then the alcohol is removed by air drying and a vacuum desiccator. 1 ml of distilled water is added to the Petri dish thus supplied with the test sample. Highly reliable results can be obtained by setting the concentration of the substance in 5 to 7 steps within the range of 1 to 500 ppm and performing duplicate tests for each concentration. Twenty-five healthy cress seeds are uniformly sown on a Petri dish containing the test sample aqueous solution. As a control, several Petri dishes prepared only with distilled water are prepared and seeded in the same manner. After a few minutes, the seeds swell and are enveloped by the jelly-like substance, so that they are firmly fixed on the filter paper. After seeding, seal each Petri dish with a lid that clearly indicates the sample name and concentration. Put these in a humid box
Place in the dark at 25 ° C. As a simpler method, about 10 Petri dishes may be put together and wrapped completely in aluminum foil and stored at a temperature of 25 ° C.

After 40 hours, the number of radicles growing by 1 mm or more is counted, and the percentage of the germination number in the control plot is calculated. This value is subtracted from 100 to obtain the germination inhibition rate. Under these conditions, 1 ppm concentration of ABA (abscisic acid) completely suppresses germination.

2) Photosynthetic electron transfer (PET) inhibition test (using spinach chloroplast) Preparation of chloroplast 100 g of spinach leaves excluding the stem portion are thoroughly washed with water, and then thoroughly rinsed with deionized water. Preparation buffer (0.4M sucrose, 5mM MgCl ₂ , 10mM Na)
Cl, 50 mM Tricine, pH 7.8) 300 ml and add about 20
After crushing for 2 seconds, it is filtered with a gauze layered on 8 layers. The filtrate is centrifuged at 6000 xg for 10 minutes in a cooling centrifuge, the supernatant is discarded, and the precipitated portion is suspended in 100 ml of buffer solution. At this time, it is possible to perform well without damaging the chloroplast by suspending the precipitated portion by loosening it with a soft tip such as a paintbrush. Then, the mixture is centrifuged at 600 × g for 2 minutes, the precipitate formed is removed, and the supernatant is used again to repeat centrifugation at 6000 × g for 10 minutes. After the operation is completed, the suspension is suspended in an appropriate amount of buffer solution to measure the chlorophyll a concentration, then put in a plastic tube, frozen and stored in liquid nitrogen, and used for the experiment. Take 1 ml from the prepared chloroplast, add 20 ml of 80% acetone water, stir well and centrifuge at 3000 xg for 10 minutes to extract chlorophyll. 649nm and 6 after extraction
The absorption luminosity at 65 nm (A ₆₄₉ , A ₆₆₅ ) was measured, and the chlorophyll concentration was determined by the following formula.

Chlorophyll (μg / ml) = 11.63 A ₆₆₅ -2.39 A ₆₄₉ PET inhibitory activity measurement For the measurement, a UV absorption measuring instrument was improved and a measuring instrument that was capable of irradiating the cuppet with light was used. The light intensity was used as the measurement condition, and the measurement was performed at room temperature. The chloroplast concentration was 0.5 μg / ml. Chloroplast easily deactivates at room temperature, so thaw it and store it in ice-cooled solution. 20 mM methylamine, 50 μM DCPIP for measurement sample solution
((Dichlorophenolindophenol) buffer (50
What was prepared using mM HEPES, 10 mM-NaCl, pH 7.0) was used, and the test compound was dissolved in ethanol and added to the measurement sample solution containing chloroplast. At that time, adjust the concentration so that the ethanol concentration is within 1.5%. Note that some compounds may require a certain incubation time before the PET inhibitory activity is expressed. After the incubation, place the cuvette on the measurement optical path and irradiate it with light.
Photoreduction of P is observed. The PET inhibitory activity of the compound was calculated by comparing the reduction amount per unit time.

〔Example〕

Synthesis of nitro compound (III) In a 500 ml reaction flask, phloroglucinol (II) (R ²
= H) 10 g, 40% nitric acid aqueous solution 200 ml, dichloromethane 200 m
Add l and stir at room temperature for 2 days.

The obtained reaction product is poured into 300 ml of ice water in a 2 liter beaker, and calcium carbonate is added to adjust the pH to 2-3.

This was extracted three times with about 2 liters of dichloromethane, dehydrated and concentrated, and then crystallized as (III) (reddish brown) as almost a single substance.
Was quantitatively obtained.

Compound (I) is stirred in nitrobenzene 200ml reaction flask _{(R = n-C 4 H} 9) Synthesis 500 ml. Add 15 g of well-ground aluminum chloride powder to this, and continue stirring until it is sufficiently dissolved (about 30
Min), after which 5 g of (II) is added and stirring is continued for about 30 minutes. All of these operations are performed in a hood at room temperature.

After that, 6 g (2 equivalents) of n-butyl isocyanate (C ₄ H ₉ NCO) is added, and the reaction is carried out at 60 to 70 ° C. overnight.

The reaction solution is poured into 200 ml of ice water and extracted with about 500 ml of dichloromethane.

The dichloromethane fraction obtained was treated with an aqueous solution of IN caustic soda 50
When 0 ml is distributed, the target product is distributed in the caustic soda aqueous solution fraction.

This aqueous layer is adjusted to pH 2-3 with hydrochloric acid, extracted with dichloromethane, dehydrated and concentrated.

When extracted with hot hexane and recrystallized from this, (III) was obtained as almost pure crystals. Yield about 60%.

For other R ¹ NCO, the target compound was obtained in a yield of 50 to 70% in the same manner. The results are shown in the following table together with the results of the bioactivity test.

[Effects of the Invention] The compound of the present invention has excellent germination inhibitory activity and photosynthetic electron transfer inhibitory activity, and is therefore useful as a herbicide.

Further, according to the method of the present invention, the target compound can be obtained in good yield.

Claims (2)

[Claims] 1. A 3-nitro- represented by the following general formula (I):
2,4,6-Trihydroxybenzamide. (In the formula, R ¹ represents an alkyl group or a cycloalkyl group, and R ² represents a hydrogen atom or a lower alkyl group.) 2. The following general formula (II): (In the formula, R ² represents a hydrogen atom or a lower alkyl group.) The compound represented by the general formula (II
I): The compound represented by the formula (IV): R ¹ NCO (IV) (wherein R ¹ represents an alkyl group or a cycloalkyl group) is reacted with the compound represented by the formula (IV): With general formula (I): (In the formula, R ¹ and R ² are the same as above.) A method for producing 3-nitro-2,4,6-trihydroxybenzamide.