Isothiocyanato derivatives of sugars in the stereoselective synthesis of spironucleosides and spiro-C-glycosides

A stereocontrolled synthesis of pyranoid and furanoid spironucleosides and spiro-C-glycosides (d-ribo and d-arabino configurations) of oxazolidines, oxazolines and perhydrooxazines via isothiocyanato sugar derivatives is reported. The intermediate isothiocyanates are prepared from sugar spiroketals by stereoselective opening of the acetal ring with trimethylsilyl N- and C-nucleophiles, and later formation of the isothiocyanato group.