O. S. El’tsov

Synthesis of A-Pentacyclic Triterpene α,β-Alkenenitriles

A-seco-triterpenoids with a methylketone group were synthesized from epimeric 3-hydroxy-3-methyl-1-cyano-2,3-seco-triterpenoids of the lupane and 19β,28-epoxy-18αH-oleanane types, which were formed by a Grignard reaction. The resulting methylketones underwent under base-catalysis conditions an intramolecular cyclization to form A-pentacyclic β-substituted alkenenitriles. The synthesized compounds included 3-methyl-1-cyano-19β,28-epoxy-2,3-seco-2-nor-18αH-olean-3-one and methyl 3-methyl-1-cyano-2-norlup-1(3),20(29)-dien-28-oate, which inhibited in vitro reproduction of human immunodeficiency virus type 1.

Synthesis of 1,3,4,6-tetraoxo compounds

The two-step method of synthesis of 1,3,4,6-tetraoxocompounds with different terminal substituents is developed. By condensation of alkyl methyl ketones with dimethyl oxalate new 1,6-dialkyl-substituted 1,3,4,6-tetraoxohexanes are obtained. The esters of 3,4,6-trioxoalkanoic acids are synthesized by the condensation reaction of alkyl acetates with dialkyl oxalates and alkyl methyl ketones. By the reaction of ethyl acetate with diethyl oxalate and methyl acetate the mixed diester of 3,4-dioxo-1,6-hexanedioic (ketipic) acid has been first prepared. Specific structural features of the synthesized compounds are discussed basing on the data of the IR, NMR, and XRD diffraction (XRD) analysis.

Method of synthesis and structure of (5E)-5-(2-alkoxy-2-oxoethylidene)-4-hydroxy-2,2-dimethyl-1-(4-methylphenyl)-2,5-dihydro-1H-pyrrole-3-carboxylates

A procedure has been developed for the synthesis of dialkyl (5E)-5-(2-alkoxy-2-oxoethylidene)-4-hydroxy-2,2-dimethyl-1-(4-methylphenyl)-2,5-dihydro-1H-pyrrole-3-carboxylates by three-component condensation of dialkyl 3,4-dihydroxyhexa-2,4-dienedioate with acetone and p-toluidine. The structure of the products is discussed on the basis of the IR, 1H NMR, and X-ray diffraction data.

Synthesis, photochemical and luminescent properties of (E)-2-(2-hydroxyarylethylene)-3-phenylquinazolin-4(3H)-ones

Photoinduced transformations of 2-styrylquinazolinones in solutions were studied using absorption and NMR spectroscopy methods. A possibility of control of the photochemical isomerization rate of quinazolinone 2-(hydroxyaryl)ethenyl derivatives by changing the pH of the medium was demonstrated. The bases and the solvent nature also affect the luminescence intensity of solutions of these compounds in the wavelength range of 550—650 nm. The differences in the steric organization of the ortho-hydroxystyryldiazinone system in crystals and in solutions related to the turn of the aryl group were found. Their influence on the competing processes of luminescence and photochemical transformation of the ethylene fragment were shown. The fact of reversible photo/thermal E-Z-isomerization was established for (E)-2-(2-hydroxystyryl)-3-phenylquinazolin-4(3H)-one.

Reactions of Malonothioamide Derivatives with Azides

The reactions of primary and tertiary malonothioamides with aryl and sulfonyl azides can take place in three directions, depending on the nature of the thioamides and azides. Ethoxycarbonylthioacetamide reacts with aryl azides with the formation of ethyl 5-amino-1-aryl-1,2,3-triazole-4-carboxylates. In reaction with aryl azides tertiary thioamides of cyanoacetic acid form 5-amino-1-aryl-1,2,3-triazole-4-carbothioamides, and in reaction with tosyl azide they form 5-amino-4-carboxamidino-1,2,3-thia-diazoles. Hypothetical mechanisms for the transformations are discussed.

Reaction of 1,3,4,6-tetraketones with p-toluidine and benzaldehyde

Reactions of 1,6-diphenylhexane-1,3,4,6-tetraone, octane-2,4,5,7-tetra-one, and decane-3,5,6,8-tetraone with a mixture of p-toluidine and benzaldehyde afforded, respectively, 2-[4-benzoyl-3-hydroxy-1-(4-methylphenyl)-5-phenyl-1H-pyrrol-2-yl]-1-phenylethanone, (1E)-1-[4-acetyl-3-hydroxy-1-(4-methylphenyl)-5-phenyl-1,5-dihydro-2H-pyrrol-2-ylidene]propan-2-one, and 2-hydroxy-1-(4-methylphenyl)-2-(2-oxobutyl)-4-propanoyl-5-phenyl-1,2-dihydro-3H-pyrrol-3-one.

Synthesis of Vinyl-Containing Lupane- and a-Secolupane-Type Triterpene Esters

Vinyl-containing lupane- and oleanane-type C-3 and C-28 esters were synthesized from betulin and A-secotriterpene alcohols. The reaction of 2,3-secolupane alcohol 5 with vinylacetic acid produced ester 8 and a recyclization product, methyl 2β,3β-dihydroxylup-20(29)-en-28-oate (13), which was formed quantitatively in the reaction of 5 with maleic acid.

Direct Modification of Quercetin by 6-Nitroazolo[1,5-a]Pyrimidines

Quercetin is the most well-known flavonoid and is widely distributed in the plant world. It possesses a broad spectrum of biological activity including anti-allergic, antiulcer, cardiovascular, and antipyretic [1]. Furthermore, quercetin itself and its derivatives are effective against HIV [2], SARS [3], HCV [4], and several other dangerous viruses because flavonoids inhibit key enzymatic systems [5–7]. Recently, the number of publications on its transformation has increased sharply. According to Reaxys, 870 compounds based on quercetin were synthesized from 1888 to the present. About 361 articles were published. The number of new compounds since 2002 is 749 (described in 202 publications). However, the types of reactions that have been used are exceedingly limited and represented mainly by acylation [6, 8–10], alkylation [7], glycosylation [11], and aminoalkylation [8] despite the significant volume of work on quercetin transformations. Also, the introduction of nitrogen heterocycles, i.e., structural analogs of natural purines, is a highly acclaimed method for increasing the biological activity of natural compounds. This broad class of compounds also comprises 1,2,4-triazolo[1,5-a]pyrimidines, which exhibit high antiviral activity [12–14]. Herein we report the addition to quercetin of 6-nitroazolo[1,5-a]pyrimidines as structural analogs of natural purines. We showed previously [15] that 6-nitroazolo[1,5-a]pyrimidines activated by a nitro group react with resorcinol and phloroglucinol to give products from stable addition at the heterocycle 7-position. We found during the work that quercetin (2) reacted with 6-nitroazolo[1,5-a]pyrimidines 1a–d in refluxing AcOH–EtOH (1:1) in 4 h to form stable adducts (course of reaction monitored by TLC using CHCl3–MeOH, 9:1) as racemates. The two-center phloroglucinol moiety in 2 creates the possibility of forming two regioisomeric products at C-6 and C-8 .

Synthesis and structure of 2,2′-(2-hydroxy-2H-1,4-benzoxazin-2-yl-3-ylidene)diacetic acid esters

Dialkyl 3,4-dioxohexanedioates react with 2-aminophenols to give (2′Z)-2,2′-(2-hydroxy-2H-1,4-benzoxazin-2-yl-3-ylidene)diacetic acid esters. The product structure is discussed on the basis of the IR and 1H NMR spectral data.

Features of the reaction of 3,4-dihydroxy-6-oxo-2,4-alkadienoic acid esters with acetone and p -toluidine

Three-component reactions of 3,4-dihydroxy-6-oxo-2,4-alkadienoic acids with acetone and p-toluidine were studied; their specific feature was the formation of the regioisomeric esters of 4-hydroxy-2,2-dimethyl-1-(4-methylphenyl)-5-(2-oxoalkyliden)-2,5-dihydro-1H-pyrrole-3-carboxylic acids and [4-alkanoyl-3-hydroxy-5,5-dimethyl-1-(4-methylphenyl)-1,5-dihydro-2H-pyrrol-2-ylidene]acetic acid. Structure of the synthesized compounds was discussed based on the data of IR and 1H NMR spectroscopy and X-ray diffraction analysis.