The synthesis of 5-C-(6-deoxy-1,2:3,4-di-O-isopropylidene-α-D-galactopyranos-6-yl)-2,3-O-isopropylidene-D-allo-pentofuranose

Article abstract of DOI:10.1016/S0008-6215(00)90560-3

Three approaches to the synthesis of deaminotunicamine and derivatives were developed.Tin tetrachloride condensation of 6-deoxy-1,2:3,4-di-O-isopropylidene-α-D-galacto-heptodialdo-1,5-pyranose with 2-(trimethylsilyloxy)furan gave a mixture of stereoisomeric precursors.Condensation of 1,2:3,4-di-O-isopropylidene-α-D-galacto-hexodialdo-1,5-pyranose with the phosphate carbanion obtained from diethyl (2-furyl)methoxymethyl phosphonate led to 6-deoxy-7-C-(2-furyl)-1,2:3,4-di-O-isopropylidene-L-glycero-α-D-galactoheptopyranose (13).This was converted, via the "Δ²"-butenolide route, to a mixture of stereoisomeric 5-C-(6-deoxy-α-D-galactopyranos-6-yl)-pentono-1,4-lactones of the D-allo-and D-talo configuration.In the third approach, 13 was transformed by the "enulose" approach to deamino-tri-(o-isopropylidene)tunicamine.