ON THE USE OF (4S,5S)-2-PHENYL-4,5-DIMETHYL-4-FORMYL-4,5-DIHYDRO-OXAZOLE IN THE SYNTHESIS OF N-PROTECTED 2,3,4,6-TETRADEOXY-4-C-METHYL-4-AMINO-L-HEXOSE DERIVATIVES

The (4S, 5S)-2-phenyl-4,5-dimethyl-4-formyl-4,5-dihydro-oxazole (4), via the alpha, beta-unsaturated ester 5 and re-face addition of nitrogen and sulfur nucleophiles, gave eventually the ribo-imidazolino hexose 15 and the methyl alpha and beta-2,3,4-6-tetradeoxy-4-C-methyl-4-trifluoroacetamido-3-thia-L-ribo-hexopyranoside (16). Addition via the adduct 17 afforded the arabino-3,4-diamino derivative 20 and the ribo isomer 20a, the 3-fluoro-L-ribo product 22, the 2,3-unsaturated L-hexose 21 and the erythro-2,3,4,6-tetradeoxy compound 23. The conformational feature, in solution, of the reported L-hexoses is also discussed on the basis of their H-1 NMR data.