Synthesis of a conformationally rigid isomaltose analogue: remarkable example of enantioselective glycosylation

Abstract

The synthesis of the dihydroxydecalin 2 has been accomplished based on intramolecular nitrile oxide cyclization using the nitro cyclohexene derivative 13 in 29% overall yield. Several glycosylation reagents and promoters using the diol 2 as aglycone and activated derivatives of tetra-O-benzyl-D-glucopyranose as glycosyl donors were investigated for the selective monoglucosylation of 2(i.e., enantioselective glycosylation) giving preferably the R-COH glycoside 1, which represents a rigid analogue of isomaltose. Trimethylsilyl trifluoromethanesulphonate (TMSOTf) and tetra-O-benzylglucopyranose 1-acetate proved to be the best, and gave, under thermodynamic control, excellent regioselectivity and acceptable stereoselectivity.