2,4-DISUBSTITUTED PYRROLO[2,3-D]PYRIMIDINE ALPHA-D-RIBOFURANOSIDE AND BETA-D-RIBOFURANOSIDE RELATED TO 7-DEAZAGUANOSINE

Nucleobase‐anion glycosylation (KOH, tris[2‐(2‐methoxyethoxy)ethyl]amine (TDA‐1), MeCN) of the pyrrolo[2,3‐d]pyrimidines 4a–d with 5‐O‐[(1,1‐dimethylethyl)dimethylsilyl]‐2,3‐O‐(1‐methylethylidene)‐α‐D‐ribo‐furanosyl chloride (5) gave the protected β‐D‐nucleosides 6a–d stereoselectively (Scheme 1). Contrary, the β‐D‐halogenose 8 yielded the corresponding α‐D‐nucleosides (9a and 9b) apart from minor amounts of the β‐D‐anomers. The deprotected nucleosides 10a and 11a were converted into 4‐substituted 2‐aminopyrrolo[2,3‐d]‐pyrimidine β‐D‐ribofuranosides 1. 10c, 12, 14, and 16 and into their α‐D‐anomers, respectively (Scheme 2). From the reaction of 4b with 5, the glycosylation product 7 was isolated, containing two nucleobase moieties. Copyright © 1990 Verlag GmbH & Co. KGaA, Weinheim