Selective phosphitylation of the primary hydroxyl group in unprotected carbohydrates and nucleosides.

[reaction: see text] Carbohydrates and nucleosides containing a phosphate at the less-hindered primary hydroxyl group are often prepared using a protection/deprotection strategy. Herein we report that the phosphoramidite method can be used to selectively incorporate phosphorus at the primary hydroxyl group of O-unprotected carbohydrates and nucleosides; in situ oxidation of the resulting phosphite triester yields the phosphate triester.