Pyrazolopyrimidine nucleosides. Part II. 7-Substituted 3-β-D-ribofuranosylpyrazolo[4,3-d]pyrimidines related to and derived from the nucleoside antibiotics formycin and formycin B

Abstract

A number of 7-substituted 3-(β-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidines have been prepared from 3-(β(D-ribofuranosyl)pyrazolo[4,3-d]pyrimidin-7-one (formycin B). Formycin B was converted into 7-chloro-3-(β-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidine (5) by acetylation, chlorination, and subsequent deacetylation. Nucleophilic displacement of the 7-chloro-group furnished 7-hydroxyamino-(7b) 7-trimethylammonio-(7c), and 7-hydrazino-3-(β-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidine (7a). Direct alkylation of 3-(β-D-ribofuranosyl)-pyrazolo[4,3-d]pyrimidine-7-thione (6) prepared from compound (5) furnished 7-methylthio-(8a) and 7-allylthio-3-(β-D-ribofuranosyl)pyrazolo[4,3-d]pyrimidine (8b). The biological significance of these nucleosides is discussed as well as a number of discrepancies which exist between our data and previous reports.