Redox glycosidation: the use of Nozaki-Takai methylenylation in a highly stereoselective synthesis of sucrose

Article abstract of DOI:10.1016/0008-6215(92)80059-A

Sequential reaction of 2,3,4,6-tetra-O-benzyl-D-glucopyranose (7) with butyllithium and 2-<2,3,5-tri-O-benzyl-4-O-(tert-butyldiphenylsilyl)-D-arabinonoyl>thio-3-nitropyridine (6) at -78 deg C gave 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl 2,3,5-tri-O-benzyl-4-O-(tert-butyldiphenylsilyl)-D-arabinonate (8: 71percent, α:β > 50:1).Ester carbonyl methylenylation, desilylation, and iodoetherification in the presence of silica gave 3,4,6-tri-O-benzyl-1-deoxy-1-iodo-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl)-β-D-fructofuranoside (15: 44percent, α:β > 50:1).This neopentylic iodide 15 was converted into sucrose (1: 80percent) by free-radical substitution using TEMPO (24) followed by sodium-ammonia reduction, acetylation and Zemplen methanolysis.