Stereoselective Synthesis of P-Modified α-Glycosyl Phosphates by the Oxazaphospholidine Approach

α-Glycosyl phosphate derivatives are widely known as constituents of biomolecules. To date, several types of non-natural α-glycosyl phosphates including "P-modified analogs" have been synthesized to investigate their characteristics. Herein a new approach to the stereoselective modification of the intersugar phosphorus atom in α-glycosyl phosphates by use of the oxazaphospholidine method is presented. Via this approach, the dimers of α-glycosyl phosphorothioates and α-glycosyl boranophosphates were obtained efficiently and stereoselectively.