Acetals I. cyclohexylidenation of glycerolyl flavazoles and the galactosyl derivative of the D-erythro analogue

Cyclohexylidenation of 3-[D and L-threo-glycerol-1-yl]-phenylflavazole gave in both cases 2 products, alpha-terminal and alpha-threo- cyclohexylidene rings which afforded the corresponding monoacetyl derivatives upon acetylation. Similarly 3-[D-erythro- glycerol-1-yl]-1-phenylflavazole gave 2,3-O-cyclohexylidene derivative, which formed an acetate upon acetylation. While 3-[1-O-[beta-D-galactopyranosyl]-D-erythro- glycerol-1-yl]-1-phenylflavazole gave the corresponding 3',4',2,3-di-O- cyclohexylidene derivative, whose acetylation and oxidation were studied

Reaction of 6-aryl-5-cyano-2-hydrazine-3,4-dihydro-pyrimidin-4-one with mono and dicarbonyl compounds

The reaction of 5-cyano-2-hydrazino-6-[p-methoxyphenyl]- 3,4-dihydropyrimidin-4-one [I] with formic acid gave the triazolo [1,5-a] pyrimidinone derivative III. Its reaction with triethyl orthoformate gave the triazolo [4,3-a] pyrimidinone derivative V. Reaction of N-methylpyrimidinone derivative VI with formic acid gave the formylhydrazino derivative VII, while its reaction with triethyl orthoformate gave VIII where cyclization took place on N-1. Treatment of I with acetaldehyde formed the hydrazone XIII, which was cyclized to the triazolo [1,5-a] pyrimidinone XIV. Diazotization of I gave the azide derivative XVIII, which on boiling in Ac2O gave the tetrazolo [1,5-a] pyrimidinone XIX. Reaction of I with carbon disulfide in pyridine or in acetonitrile gave the two isomeric triazolopyrimidinones [1,5-a] and [4,3-a], XXIII and XXIV, respectively. Condensation of I with different chalcones gave the pyrazolinyl pyrimidine derivatives XXVI-XXVIII

Mechanism and absolute configuration of benzylidene derivatives of some acyclic C-Nucleosides

The mechanism of formation of benzylidene derivatives was deduced from the mode of the condition of benzylidenation as well as from their assigned structures. The absolute configuration has been assigned to the various isomeric forms for each diastereoisomer. The protection of hydroxyl groups in a polyhydroxymolecule can be achieved by various ways, e.g. by acylation and/or acetalization. The latter protecting groups possess the advantage, in most cases, of being stable towards, alkaline conditions but could be successively cleaved under acidic conditions, whereas, the acylated products possesses a reverse character. Acetalization may promise the direct protection of two hydroxyl groups out of three or more existing in the same molecule. Perprotection of the hydroxyl groups can be easily accomplished without much problems, whereas their partial protection needs much care and it is very important in organic synthesis