Synthesis of L-trehalose and observations on isomer and by-product formation

With a view to gaining evidence on the mechanism by which D-trehalose is able to stabilise biomolecules towards dehydration (anhydrobiosis) and heat, L-trehalose has been prepared in order to allow comparative studies to be made. Little change can be induced in the ratio of the α,α-, α,β-, β,β-1,1′-stereoisomers of the disaccharide formed from 2,3,4,6-tetra-O-benzyl-L-glucose by using different reaction procedures and by varying the reaction conditions. Benzyl 2,3,4,6-tetra-O-benzyl α- and β-L-glucopyranoside are by-products in the trimethylsilyl trifluoromethanesulphonate mediated formation of the 1,1′-linked disaccharides.