Synthesis of sugar-derived isoselenocyanates, selenoureas, and selenazoles

Aryl, alkyl, and sugar-derived isoselenocyanates were prepared by a one-pot procedure starting from the corresponding formamides, using triphosgene as a dehydrating agent, triethylamine, and black selenium powder. The preparation of sugar selenoureas by coupling of O-protected sugar-derived isoselenocyanates with different amines, and by coupling of unprotected glycopyranosyl amines with phenyl isoselenocyanate was also accomplished. The synthesis of a glucopyranos-2-yl-selenazole starting from O-protected 2-amino-2-deoxy-d-glucose by coupling with benzoyl isoselenocyanate, Se-alkylation with phenacyl bromide, and acid-catalyzed dehydration is also reported. Unprotected N-(β-d-glucopyranosyl)-N′-phenylselenourea was transformed into a 1,2-trans-fused bicyclic isourea upon treatment with aqueous hydrogen peroxide; the same isourea was prepared by a one-pot three-step procedure from β-d-glycopyranosylamine by thiophosgenation, coupling with aniline, and HgO-mediated desulfurization.