Reaction of 1‐(2′,3′‐epoxy‐β‐ D ‐lyxofuranosyl)uracil with hydrogen fluoride. The unexpected formation of 1‐(3′‐fluoro‐3′‐deoxy‐β‐ D ‐ribofuranosyl)uracil

Reaction of 1‐(2′,3′‐epoxy‐β‐ D ‐lyxofuranosyl)uracil ( 1 ) with hydrogen fluoride afforded 3′‐fluoro‐3′‐deoxyarabinouridine ( 2 , 13%) and 3′‐fluoro‐3′‐deoxyuridine ( 3 , 11%). The structure of 3 was assigned from spectrometric data and confirmed by an unambiguous synthesis from 2′,5′‐di‐ O ‐trityl‐2,3′‐anhydrouridine ( 5 ) and hydrogen fluoride.