Synthesis of β-analogues of C-mannosyltryptophan, a novel C-glycosylamino acid found in proteins

Abstract

α-C-Mannosyltryptophan (α-C-Man-Trp) has been found to be a novel post-translational modification of tryptophan found from some biologically important glycoproteins. In order to analyze the biological functions of α-C-Man-Trp, we have developed an efficient synthetic strategy for α-C-Man-Trp and its glucose and galactose analogues, starting from α-C-glycosidation of the corresponding hexapyranoside derivatives with tinacetylene. According to the synthetic routes, we describe here syntheses of β-anomers of C-Man-Trp, and its glucose and galactose analogues from the corresponding β-C-glycosylacetylenes. During this study, we have developed a highly stereocontrolled synthesis of β-C-mannosylacetylene that is required for the synthesis of β-C-Man-Trp, while the precedented method gave an anomeric mixture of the C-mannosylacetylene. The synthetic C-Man-Trp and its analogues were analyzed by HPLC.