A new synthesis of nitroketene aminals

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, p. 2660, November, 1990.     

Competitive formation of 4-aminoisoxazoles and 5-aminooxazoles in the cyclization reactions of O-alkylated hydroxyimino nitriles

Base-catalyzed cyclization of O-alkylated α-hydroxyimino nitriles gave mixtures of 4-aminoisoxazoles and 5-aminooxazoles, their ratio depending on the substituent structures and the reaction conditions. The formation mechanism of 5-aminooxazoles in this reaction is discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1773–1780, October, 2006.     

Synthesis of α-functional nitro compounds by the nitration of activated carbonyl compounds in a two-phase system

2-Nitro-1,3-dicarbonyl and -nitromonocarbonyl compounds were synthesized in the yields varying from moderate (30 %) to nearly quantitative by the nitration of -dicarbonyl compounds in a two-phase system: sulfuric/nitric acid mixture-chloroform at - 10÷10 °C. The use of phase transfer conditions made it possible to avoid the formation of furoxans as by-products and to simplify the isolation of products. This method is quite common for preparing various -functional nitro compounds including those containing a CF₃-group. Key words: nitration, -functional nitro compounds.Translated fromIzvestiya Akademn Nauk. Seriya Khimicheskaya, No. 1, pp. 76–79, January, 1994.     

DETECTION OF DNA-PSORALEN PHOTOADDUCTS in situ

Abstract— An immunological method, with the use of specific immune serum, has been developed for detection of 8-methoxypsoralen (8-MOP) photoadducts to DNA, formed in situ in cell nuclei, after combined treatment with 8MOP and UV-A irradiation (Zarçbska et al. , 1978). Lymphocytes fixed on slides or in suspension, and cryostat sections of different mammalian tissues, served as antigenic substrate, after treatment with 8-MOP and UV-A in vitro. Specific fluorescence in these substrates was detected in the nuclei after treatment with 30 ˜ 140 kJ/m² UV-A in the presence of 0.1-0.3 μg/cm² 8-MOP. PHA-stimulated-lymphocytes appeared to be the most sensitive substrate.
However, hairless mice treated with high doses of UV-A in vivo , 70 ˜ 360 kJ/m² did not reveal a specific fluorescence of epidermal nuclei, unless a high local concentration of 8-MOP was attained.
The apparent discrepancy in the level of photoadduct detection between the in vitro and in vivo treated specimens was explained by the low number of DNA-8-MOP-photoadducts formed in vivo under these experimental conditions. The relevance of these findings to the role of DNA-8-MOP-photoadducts formed during PUVA photochemotherapy is discussed.     

Investigation of the regioselectivity of alkylation of 3-nitropyridin-2(1H)-ones

Alkylation of 3-nitropyridin-2(1H)-ones in the presence of bases affords N-alkylated products and sometimes O-alkylated products. The yields and relative amounts of N- and O-alkylated products depend substantially on the size of the substituent at the C(6) atom of pyridone.     

Synthesis of 4-aminoisoxazole-3-carboxamides using base-promoted nitrosation of N-substituted cyanoacetamides

The reactions of N-substituted cyanoacetamides with EtONO in the presence of an equimolar amount of EtONa afforded the corresponding sodium salts of hydroxyimino derivatives in 70—95% yields. The latter were transformed into 4-amino-5-(4-bromobenzoyl)isoxazole-3-carboxamides in 30—57% yields using the known method.     

ON QUOTIENTS OF BRAID GROUPS

ABSTRACT.

Let G be the group ?[t, t ^?1] x ?. By studying the action of the braid group B_n on the set Gⁿ , we obtain representations of B_n into a wreath product of the symmetric group and the general linear group over ?[t, t ^?1]. This in particular recovers the Burau representation of the braid group. Furthermore, some quotients of the braid group are obtained by using the representations found.     

Synthesis of heterocyclic systems with carbohydrate fragment

The reactions of levoglucosenone with amides of several -nitrocarboxylic acids and acetoacetic acid result in tetra hydropyridones fused with a carbohydrate fragment. In the case of acetoacetic acid amides, mixtures of keto and enol tautomers were obtained. The stereochemistry of cyclization is discussed in detail.For Communication 1, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 409–414, February, 1996.     

Ethyl 2-nitroacetoacetate as a new synthetic equivalent of ethoxycarbonylnitrile oxide

It was shown that ethyl 2-nitroacetoacetate is a synthetic precursor of ethoxycarbonylnitrile oxide as well as of isoxazole- and isoxazoline-3-carboxylic acids and their esters. The elimination of acetic acid from ethyl 2-nitroacetoacetate occurs in a mixture of acetic acid and acetic anhydride in the presence of strong mineral acids,e.g., H₂SO₄, at room temperature and gives isoxazolines in yields of up to 85–91 %.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 103–105, January, 1994.