Anthranils, reduced

Anthranils are readily cleaved by nitrous acid, presumably by attack of water on (V- nitroso cations. The first product that can be observed is the nitrosohydroxylamino compound (179), which becomes reduced to the diazonium salt (180) (67AHC(8)277). 

These formulae explain the scission products of the two alkaloids and the conversion of evodiamine into rutaecarpine, and were accepted by Asahina. A partial synthesis of rutaecarpine was effected by Asahina, Irie and Ohta, who prepared the o-nitrobenzoyl derivative of 3-)3-amino-ethylindole-2-carboxylic acid, and reduced this to the corresponding amine (partial formula I), which on warming with phosphorus oxychloride in carbon tetrachloride solution furnished rutaecarpine. This synthesis was completed in 1928 by the same authors by the preparation of 3-)S-amino-ethylindole-2-carboxylic acid by the action of alcoholic potassium hydroxide on 2-keto-2 3 4 5-tetrahydro-3-carboline. An equally simple synthesis was effected almost simultaneously by Asahina, Manske and Robinson, who condensed methyl anthranilate with 2-keto-2 3 4 5-tetrahydro-3-carboline (for notation, see p. 492) by the use of phosphorus trichloride (see partial formulae II). Ohta has also synthesised rutaecarpine by heating a mixture of 2-keto-2 3 4 5-tetrahydrocarboline with isatoic anhydride at 195° for 20 minutes. 

Nucleophilic aromatic substitution of the anthranilic acid derivatives, 72, on ortho-bromonitrobenzene affords the diphenyl-amine, 73. The ester is then saponified and the nitro group reduced to the amine (74). Cyclization of the resulting amino acid by heat affords the lactam (75). Alkylation on the amide nitrogen with 2-dimethylaminoethyl chloride by means of sodium amide affords dibenzepine (76). ... 

Anthranilic acid, or o-amidobenzoic acid, C H (NH2)(COOH),. is the-acid constituent of the ester found in neroli, petit-grain, jasmin, and mandarin oils. It is a solid crystalline substance melting at 145°. It is prepared artificially, and then converted into synthetic methyl anthranilate.. To prepare anthranilic acid, o-nitrobenzaldehyde is reduced by tin and hydrochloric acid to anthranil,... 

To reduce conjugative first-pass metabolism and increase the oral bioavailability of P-estradiol, estradiol-3-salicylate, and P-estradiol-3-anthranilate, ester prodrugs were synthesized and their oral bioavailabilities in dogs were evaluated... 

Replacement of the phenyl group of anthranilic acid by a cycloalkene represents another strategy to obtain intellectual property. This endeavor resulted in three consecutive patent applications [73-75] and a publication [76]. The advantages of tetrahydro anthranilic acid as a surrogate for anthranilic acid include reduced CYP2C8 and 2C9 inhibition and improved oral exposure in mice (analogs 25 vs. 12). Ultimately, a pre-clinical candidate, MK-6892 (26), was selected from this series due to its... 

Reduction of anthranilic acid (5) to o-aminobenzylalcohol (6). The expensive LiAlH4 can be used as reducing agent for valuable fine chemicals, e.g. pharmaceuticals [31]. 

Commercially, methyl anthranilate (trade name ReJeX-iT AG-36) is used to repel red-winged blackbirds, Agdaiusphoeniceus, from feeding on rice seed (Avery etal, 1995). This species avoidedmethiocarb-poisoned apples additional chemical (methyl anthranilate) and visual (calcium carbonate) cues enhanced the avoidance response. This way the amount of the toxin methiocarb could be reduced and yet still be equally effective and at lower cost (Mason, 1989). Canada geese (Branta canadensis) also feed less on grass treated with methyl anthranilate (Cummings etal, 1995). 

Reduction of aromatic carboxylic acids to alcohols can be achieved by hydrides and complex hydrides, e.g. lithium aluminum hydride 968], sodium aluminum hydride [55] and sodium bis 2-methoxyethoxy)aluminum hydride [544, 969, 970], and with borane (diborane) [976] prepared from sodium borohydride and boron trifluoride etherate [971, 977] or aluminum chloride [755, 975] in diglyme. Sodium borohydride alone does not reduce free carboxylic acids. Anthranilic acid was reduced to the corresponding alcohol by electroreduction in sulfuric acid at 20-30° in 69-78% yield [979],... 

A high yielding synthesis of anthranil from 2-nitrobenZaldehyde makes use of zinc and allyl bromide as the reducing agent. The method has also been used for the preparation of 3-substituted anthranils from 2-nitrophenyl ketones <99H(51)1921>. A solid phase synthesis of 3-aminobenzisoxazoles 15 is based on the displacement of fluoride from 2-fluorobenzonitriles by the Kaiser oxime resin and subsequent hydrolysis of the C=N bond <99JOC4547>. A synthesis of 3-(2-dialkylaminoethyl)benzisoxazoles from oximes of 2-hydroxyphenyl ketones has also been described <99H(51)2139>. ... 

Most of the nonsteroidal anti-inflammatory drugs (NSAIDs) are carboxylic acids. Aspirin (8.69) (acetylsalicylic acid, ASA) has been used since the turn of the last century to reduce pain and fever, but the parent compound, salicylic acid, has been known and used since antiquity, owing to its common occurrence as a glycoside in willow bark. Acetylation merely decreases its irritating effect. Among the numerous other salicylates known and used, flufenisal (8.70) has a longer duration of activity and fewer side effects than aspirin. Mefenamic acid (8.71) and flufenamic acid (8.72) are derivatives of anthranilic acid, while ibuprofen (8.73) and naproxen (8.74) are derivatives of phenylacetic and naphthylacetic acids, respectively. 

The first step in one synthesis of the antipsychotic dmg clozapine (37-5) involves UUman coupling of anthranUic acid (37-1) with 2,4-dichloronitrobenzene (30-1) to give the substituted anthranilate (37-2). The carboxyl group is then converted to the A-methylpiperazinamide (37-3) via a suitably activated intermediate as, for example, the imidazohde obtained by reaction with carbonyidiimidazole (CDl). The nitro group is then reduced to amine (37-4) by means of catalytic hydrogenation. Intramolecular Schiff base formation catalyzed by toluenesulfonic acid then completes the synthesis of clozapine (37-5) [38]. 

The yellow crystalline azaberbinone (388) has been prepared by several, closely related methods. Dehydrogenation of betaine 378 (Section III,E,2) with dichlorodicyanoquinone gives compound 388 directly. Alternatively, this compound (388) has been prepared in three ways from 6 -nitropapaverine (385) (Scheme 15) (i) Treatment of compound 385 with triethyl phosphite gives a low yield of betaine 388 directly (ii) compound 385 in methanolic KOH at reflux temperature gives the anthranil 386 which rearranges to the betaine 388 in hot triethyl phosphite and (iii) iodine oxidation of 6 -nitro-papaverine (385) generates the A-oxide 387 which is reduced to the betaine 388 by sodium bisulfite. The chemistry of compound 388 remains unexplored. 

A mixture of 500 g of methyl anthranilate and 438 g of 2,5-dimethoxytetrahydrofuran in 670 ml of glacial acetic acid is heated at reflux temperature for 1.5 hours. The acetic acid is then evaporated under reduced pressure and the residue is distilled to yield methyl 2-(lH-pyrrol-l-yl)benzoate, b.p. 109°C/0.1 mm Hg. 

Dilution has a significant effect in reducing the rate of the reaction, and the formation of Schiffbases is slowed down, although not entirely stopped once the compound has been diluted in alcohol. Methyl anthranilate occurs naturally in many essential oils together with aldehydes such as citral without forming Schiffbases owing to the low concentration of both materials. 

The above procedure is derived from the work of Atkinson and Lawler 6 but employs a more suitable reducing agent than that7 previously used to convert diazotized anthranilic acid to diphenic acid. The product can be resolved into its optically active forms,6 which are stable to racemization. 

These compounds form the largest group of reduced derivatives of anthranils. They are also referable to 3,4-disubstituted isoxazoles, and are prepared and react as such. 

Arylanthranils (205) have been obtained from 2-aroylbenzamides by Hofmann degradation and subsequent oxidation, using two moles of sodium hypobromite besides (205), some brominated product was isolated. The anthranil (205) could be reduced (Zn/CaCl2)tothe amino-ketone (206), which with nitrous acid gave some 205, as well as the diazonium salt.345... 

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