C-nucleoside studies. Part 10. A new synthesis of 3-(2,3,5-tri-O-benzyl-β-D-ribofuranosyl)pyrazole and its conversion into 4-nitro-3(5)-β-D-ribofuranosylpyrazole

Abstract

1,1-Diethoxy-3-(2,3,5-tri-O-benzyl-β-D-ribofuranosyl)prop-2-yne (12) has been synthesised from 2,3,5-tri-O-benzyl-D-ribofuranose in 52% yield. Acidic hydrolysis followed by reaction with hydrazine affords 3-(2,3,5-tri-O-benzyl-β-D-ribofuranosyl)pyrazole (1) in 71% yield. Mild methods have been devised for nitration of pyrazole derivatives at C-4, leading to a synthesis of 4-nitro-3(5)-β-D-ribofuranosylpyrazole (3) from (1) in 56% overall yield.