An Efficient Synthesis of 2'-O-(β-D-Ribofuranosyl)biopterin

N(2)-(N,N-Dimethylaminomethylene)-3-[2-(4-nitrophenyl)ethyl]-1',2'-di-O (trimethylsilyl)biopterin (4) was prepared from biopterin (1a, 86% overall yield) in 5 steps. Glycosylation of 4 with 1,2,3,5-tetra-O-acetyl-β D-ribofuranose (5a) and its 2,3,5-tri-O-benzoyl analog (5b) respectively afforded the corresponding 2'-O-(2,3,5-tri-Oacetyl- and 2,3,5-tri-O-benzoyl-β-D ribofuranosyl)biopterin derivatives (6a, 42% and 6b, 60%) as major products. Removal of the protecting groups of 6b provided 2'-O-(β-D-ribofuranosyl)biopterin (1c, 87% overall yield) in 3 steps.