Glycals reaction with hydrogen fluoride

The rearrangement of glycal derivatives to l-substituted 2-enose derivatives has been applied to the preparation of i) 2,3-dideoxy-i-thiohex-2-enopyranosides (9, trimethylsilylated thiols and boron trifluoride details of the complexities of the reaction are reported) ii) 2,3-dideoxyhex-2-enopyranosyl fluorides [10, pyridine poly(hydrogen fluoride)iii) 2, 3 -unsaturated nucleosides (11, purine or pyrimidine derivatives with trityl perchlorate) (Scheme 7). 

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