Sugars epithio

Epithio sugars acylation, 7, 171 hemiacetafs hydrolysis, 7, 170 Epitiostanol, 7, 182, 183 Epoxidations... 

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. 

We therefore needed a ready synthesis of the 1,6-epithio epoxide 119. Normally, for such syntheses, the sulftir atom is introduced at an early stage [64]. However, it appeared to us that a suitable doubly-activated sugar such as 120 should be capable of direct conversion to the 1,6-epithio sugar 121 by treatment with some type of sulfur reagent. Indeed, the o-glucosyl bromide 122 was easily prepared and, upon treatment with either hydrogen sulfide and triethylamine in DMF or benzyltriethylammonium tetrathiomolybdate in chloroform, gave the... 

M. Michalska, W. Kudelska, J. Pluskowski, A. E. Koziol, and T. Lis, Novel observations on thiophoshoryl-group transfer in sugar /1-hydroxy phosphorodithioate systems. Synthesis and X-ray molecular structure of l,6-anhydro-3,4-dideoxy-3,4-epithio-2-0-(p-tolylsulfonyl)-/l-D-allopyranose, J. Chem. Soc., Perkin Trans. 1, (1994) 979-983 and references therein. 

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