Stannylene activation in glycoside synthesis: Regioselective glycosidations at the primary position of galactopyranosides unprotected in the 2-, 3-, 4-, and 6-positions

Article abstract of DOI:10.1055/s-1995-3918

Stannylene activation with dibutyltin oxide of methyl D-galactopyranosides and of methyl β-D-glucopyranoside, respectively, followed by glycosidation with 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl bromide promoted by tetrabutylammonium iodide, or followed by glycosidation with ethyl 2,3,4,6-tetra-O-benzoyl-1-thio-β-D-glucopyranoside, or ethyl 2,3,4,6-tetra-O-acetyl-1-thio-β-D-galactopyranoside, or ethyl 3,4,6-tetra-O-acetyl-2-deoxy-2-phthalimido-1-thio-β-D-glucopyranoside , or ethyl 2,3,4,6-tetra-O-benzoyl-1-thio-α-D-mannopyranoside, the latter four glycosyl donors being promoted by dimethyl(methylthio)sulfonium trifluoromethanesulfonate (DMTST), led to regioselective glycosidation at the 6-OH of the stannylene glycosyl acceptors. This selectivity was not observed in the absence of stannylene activation.