Behaviour of some 1-C-acceptor-substituted glycals under azidohydroxylation conditions.

Azidohydroxylation of 1-carbamoyl, 1-methoxycarbonyl and 1-cyano substituted d-lyxo and d-arabino configured O-peracylated glycals was studied and the reaction conditions were optimized. Under these conditions (3 equiv. NaN3/2 equiv. PIFA/0.3 equiv. TEMPO/50 equiv. H2O/dry DCM/0 °C/Ar) the expected 3-azido-3-deoxy ulopyranosonic acid derivatives were isolated in good yield with α-d-galacto configuration exclusively from the reaction of the 1-carbamoyl and 1-methoxycarbonyl substituted d-lyxo configured O-peracetylated glycals, while the transformation of the 1-cyano derivative gave a 2,3-vicinal diazide in low yield. The 1-carbamoyl d-arabino configured O-perbenzoylated glycal gave a mixture of α-d-gluco and α-d-manno configured azidohydroxylated products with d-gluco preference. The analogous 1-methoxycarbonyl derivative gave an inseparable product mixture and no transformation was detected with the respective 1-cyano glycal.