Direct One-Pot Synthesis of Nucleosides from Unprotected or 5-O-Monoprotected D-Ribose.

New, improved methods to access nucleosides are of general interest not only to organic chemists but to the greater scientific community as a whole due their key implications in life and disease. Current synthetic methods involve multistep procedures employing protected sugars in the glycosylation of nucleobases. Using modified Mitsunobu conditions, we report on the first direct glycosylation of purine and pyrimidine nucleobases with unprotected D-ribose to provide β-pyranosyl nucleosides and a one-pot strategy to yield β-furanosides from the heterocycle and 5-O-monoprotected D-ribose.