Synthesis and elucidation of absolute stereochemistry of salaprinol, another thiosugar sulfonium sulfate from the ayurvedic traditional medicine Salacia prinoides

Synthesis and elucidation of absolute stereochemistry of salaprinol (3) isolated from the root and stems of Salacia prinoides, which has been used for the treatment of diabetes in India, Sri Lanka, and Southeast Asia countries, is described. Compound 3 and its 2′-epimer, epi-salaprinol (epi-3) were synthesized via the coupling reaction of a cyclic sulfate, 2-O-benzylglycerol 1,3-cyclic sulfate (5), with a thiosugar, 1,4-dideoxy-1,4-epithio-d-arabinitol (6), as the key reaction, and S configuration of the asymmetric center in the side chain of 3 was elucidated by the X-ray crystallographic analysis.