Acarbose precursor

It would, in principle, be possible to convert the polyol 115 into the 6"-deoxy sugar 118, a direct precursor of /3-acarbose. However, we decided that it would be better to reassess the whole synthesis and reasoned that a 1,6-epithio sugar such as 119 would be an ideal pivot for a synthesis of acarbose the amine 81 could easily be introduced at C-4, the sulfur at C-1 allows for activation to produce a glycosyl donor ready for attachment to the disaccharide alcohol 113 and, finally, desulfurization at C-6 leads to the necessary methyl group. 

Acarviosin 441, an a-glycosidase inhibitor, is a maltose-type pseudodisaccharide that can be prepared from methanolysis of acarbose 442 [255]. It has been shown to have five times more inhibitory activity than its precursor acarbose, for which the first total synthesis has been described by Ogawa s group in 1989 [256]. 

---