Synthesis of furan 4′-thio-C-nucleosides, their methylsulfonium and sulfoxide derivatives. Evaluation as glycosidase inhibitors

A series of furan C-nucleosides having a sulfur atom in the sugar ring were synthesised. The α and β anomers of 3-ethoxycarbonyl-2-methyl-5-(4′-thio-d-erythrofuranosyl)furans and were obtained by acid treatment of (4′-S-acetyl-4′-thio-d-arabino-tetritol-1-yl)furan . Oxidation of with m-chloroperbenzoic acid gave sulfoxide as one epimer at the sulfur atom whereas was transformed into sulfoxide as an epimeric mixture. S-Methylation of and with methyl triflate led to sulfonium salts and . The prepared compounds were found to be moderate inhibitors of α-l-fucosidase.