Highly efficient synthesis of 1-thioglycosides in solution and solid phase using iminophosphorane bases

Disaccharides of 1-thioglycosides, an important class of glycomimics, can be synthesized by direct S-alkylation in exceptionally high yields when iminophosphorane bases are employed. The reaction conditions employed appear to be general and stereospecific. Axial and equatorial 4-triflates and primary tosylates of alkyl pyranosides provided excellent yields of thio-disaccharides without substantial elimination products. The iminophosphorane bases also proved to be useful in solid support-bound couplings of thioglycosides though with lower efficiency.