Chemical modification of trehalose. Part II. Synthesis of the galacto-analogue of trehalose

Abstract

4,6:4′6′-Di-O-ethylidene- and -di-O-benzylidene derivatives of trehalose were benzoylated, and the acetal groups were removed. The resulting 2,2′,3,3′-tetra-O-benzoyltrehalose was then converted into either the 4,4′,6,6′-tetra-O-methanesulphonate by methylsulphonylation or into the 4,4′-di-O-methylsulphonyl-hexabenzoate by sequential selective di-O-benzoylation and methylsulphonylation. Treatment of either of these with sodium benzoate in hexamethylphosphoric triamide gave, with inversion of configuration at the 4- and 4′-positions, the galacto-analogue of trehalose as the octa-O-benzoate. De-O-benzoylation gave the crystalline disaccharide α-D-galacto-pyranosyl α-D-galacto-pyranoside (galacto-trehalose).