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2-Aryl- and 2-furyl-4-carboxy-1,3-thiazolidines were synthesized. Their spectral properties were studied, and conformational analysis was performed. It was shown that they exist in solution as an equilibrium of neutral and zwitter-ion forms. The influence of the nature of substitutents and of their location in a benzene ring of thiazolidines as ligands of rhodium complexes on acetophenone hydrosilylation with diphenylsilane was examined. Thiazolidines containing donor substituents in the para-position of the benzene ring were found to be the most effective; maximal asymmetrical induction (55% ee) was reached in the presence of 2-(4-methoxyphenyl)-4-carboxy-1,3-thiazolidine.

5-Fluoro-4-hydroxy-2-methoxypyrimidine exists in a solution as two oxo tautomers with the conjugated and isolated double bonds in the ring. The latter tautomer has a zwitterionic structure, and it dominates in water and trifluoroethanol. 5-Fluoro-4-hydroxy-2-methoxypyrimidine in acidic medium gives rise to an equilibrium mixture of two protonated forms at a ratio of about ∼1:1. The zwitterionic structure of 4-hydroxypyrimidines is stabilized if the solvent is capable for specific solvation via hydrogen bonding.

Methylation of 5,7-dihydro-4H-pyrano[2,3-d:6,5-d']dipyrimidine-4,6(3H)-dione and its 5-phenyl analog with dimethyl sulfate in the presence of LiOH in aqueous solution gives rise to the corresponding 3,7-dimethyl derivatives. The same isomers are formed by methylation of 5-phenyl-5,7-dihydro-4H-pyrano[2,3-d:6,5-d']dipyrimidine-4,6(3H)-dione with methyl iodide in the presence of K2CO3 in N,N-dimethylacetamide. However, with ethyl bromide, propyl iodide, or butyl bromide instead of methyl iodide, mixtures of 3,7- and 1,7-dialkyl-5-phenyl-5,7-dihydro-4H-pyrano[2,3-d:6,5-d']dipyrimidine-4,6-diones were obtained.

The reaction of 2,4,6-tris(trimethylsiloxy)pyrimidine with 2-oxabutane-1,4-diyl diacetate in methylene chloride in methylene chloride in the presence of SnCl4 proceeds regioselectively to form 1-[(2-acetoxyethoxy)methyl]barbituric acid. The latter is readily deacetylated to a free acyclic analog of N-ribosides of barbituric acid. 1-[(2-Acetoxy- and 2-hydroxyethoxy)methyl]barbituric acids easily react with aromatic and heterocyclic aldehydes in water and organic solvents, forming 5-ylidenebarbituric acids. The structure of the products was proved by 1H NMR and UV spectroscopy. Certain of the products exhibit a moderate antimicrobial and antiviral activity.

13C NMR spectroscopy was used to study the stereoselectivity of glycosylation of phenols with the α and β anomers of penta-O-acetyl-D-glucopyranose, penta-O-trifluoroacetyl-D-glucopyranose, and 2,3,4,6-tetra-O-acetyl-1-O-trifluoroacetyl-D-glucopyranose in the presence of boron trifluoride etherate at varied temperature, time, and catalyst amount. The boron trifluoride etherate-catalyzed reaction of penta-O-acetyl-β-D-glucopyranose and 2,3,4,6-tetra-O-acetyl-1-O-trifluoroacetyl-β-D-glucopyranose with phenols occurs with a high stereocontrol to give, depending on conditions, predominantly 1,2-cis- or 1,2-trans-arylglycosides. This reaction can be used for preparative synthesis of the α- and β-anomeric forms of glycosides of a wide range of phenols.

Peaks of molecular ions that generally have the maximum intensity are observed in the mass spectra of most of the investigated 5- and 6-substituted uracils and 5-substituted orotic acids and their deutero analogs and methylated derivatives. The principal pathway of the fragmentation of the molecular ions is retrodiene fragmentation with the formation of [O=C(4)C(5)R5C(6)R(6)N(1)R1]+ (F1) ions. The stabilities of the latter depend on the nature and position of the substituents attached to the C(5) and C(6) atoms. The fragmentation of the F1 ions can be realized via four principal pathways (B-E) with the detachment of N-CR6 (B), O=C=CR5 (C), CO (D), and R6 (E) fragments. The most general pathway for the fragmentation of 5-substituted uracils is pathway C, whereas the most general pathway for 6-substituted uracils is pathway E. In the spectra of 5-substituted orotic acids the intensities of the molecular-ion peaks are high (∼100%) only in the case of electron-donor R5 and decrease sharply with an increase in the electron-acceptor strength of the substituent. The principal pathways of fragmentation of the molecular ions are decarboxylation (F) and retrodiene fragmentation (A), the contribution of which is appreciably smaller. The M-CO2 ions formed after decarboxylation undergo fragmentation via a scheme similar to that observed for 5-substituted uracils.

5-Arylazo and 5-arylideneamino-2,4,6-triaminopyrimidines and their 6-hydroxy analogs were obtained by azo coupling of 2,4,6-triamino- and 2,4-diamino-6-hydroxypyrimidines with aryldiazonium salts, and also by the reaction of benzaldehydes with 2,4,5,6-tetraamino- and 2,4,5-triamino-6-hydroxypyrimidines, respectively. According to spectral data, in solvents with different polarity, these compounds exist preferentially in the triamino- or diaminohydroxy form. The main paths of the mass spectrometric fragmentation of the compounds studied have been determined.

The reaction of 2, 4, 5-triamino-6-hydroxypyrimidine with phosphorus pentasulfide in quinoline has yielded 2, 4, 5-triamino-6-mercaptopyrimidine. 8-Hydroxymethyl derivatives of guanine and thioguanine have been synthesized by the acylation of 2, 4, 5-triamino-6-hydroxypyrimidine and the corresponding 6-mercapto compound with glycolic acid or ethyl glycolate, with subsequent treatment of the resulting 5-hydroxyacetylamino derivatives with aqueous alkali.

The synthesis of β-(8-guanyl)propionic acid and its chloride, methyl ester, bis(2′-hydroxyethyl)amide, and bis(2′-chloroethyl)amide has been effected. The latter readily rearranges under certain conditions into 2′-chloroethylaminoethyl β-(8-guanyl)propionate.

Condensation of 5,6-diaminouracil with ethyl cyanoacetate yields xanthine-8-acetonitrile which is hydrolyzed by alkalis to xanthine-8-acetic acid. Also synthesized were its ethyl ester, acid chloride, and bis(2′-hydroxyethyl)amide.