2-amino-7-β- d-arabinofuranosyl-4-methoxy-7 H-pyrrolo[2,3- d]pyrimidine: A facile preparation and anomerisation of a 7-deazapurine nucleoside

Abstract

Phase-transfer glycosylation of 2-amino-4-methoxy-7 H-pyrrolo[2,3- d]pyrimidine with 2,3,5-tri- O-benzyl- d-arabinofuranosyl bromide in benzene—50% aqueous sodium hydroxide—tetrabutylammonium hydrogensulfate gave two anomeric glycosylation products ( 1 and 3). Removal of the benzyl groups from 1 and 3, respectively, with boron trichloride yielded 2-amino-7-(α- and β- d-arabinofuranosyl)-4-methoxy-7 H-pyrrolo[2,3- d]pyrimidine ( 4 and 2). Treatment of 2 and 4 with 2 m hydrochloric acid under nitrogen caused anomerisation and demethylation without glycosylic cleavage, and reflected the extraordinary stability of pyrrolo[2,3- d]pyrimidine nucleosides towards hydrolysis. The conversion of 2 and 4 into ara-7-deazaguanosine or its α anomer was accomplished with anhydrous acid.