Synthesis of saccharomimetic fucopyranosyl -substituted urethanes and ureas from glycopyranosyl nitromethanes and cyanides

Part I . Mechanistic intermediates were discovered in the Henry condensations of partially and non-protected pyranoses with a free anomeric hemiacetal function with nitromethane in various solvents for the syntheses of C-glycopyranosides in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)/molecular sieves catalyst system. Part II . Syntheses of glycosyl cyanides were optimized with a new catalyst system. Mechanism of cyanation with trimethylsilyl cyanide (TMS-CN) in the presence of the mild and recyclable Lewis acid HgBr 2 in nitromethane were proposed for the syntheses of 1,2-trans per- O -acetylated C-glycopyranosyl cyanides. Part III . Tri-O-acetyl-β-L-fucopyranosyl cyanide and Pd-H 2 , in presence of BOC-anhydride, gave N-BOC-mono- and -di-(2,3,4-tri-O-acetyl-β-L-fucopyranosylmethyl)-amines, which allow for the syntheses of small cluster oligosaccharide mimetics of fucopyranosylomethyl-substituted ureas. From di-(2,3,4-tri-O-acetyl-β-L-fucopyranosylmethyl) amine was also prepared a carbamoyl chloride as potentially useful synthon for preparation of more complex C-glycosidic conjugates.