Unexpected Dehalogenation of 3-Bromopyrazolo[3,4-d]pyrimidine Nucleosides During Nucleobase-Anion Glycosylation
作者:Frank Seela、Matthias Zulauf、Georg Becher
DOI:10.1080/07328319708001351
日期:1997.3
The anion-glycosylation (KOH, MeCN, TDA-1) of 3-bromopyrazolo[3,4-d]pyrimidines 4a and 4b with 2-deoxy-3,5-di-O-(p-toluoyl)-alpha-D-erythro-pentofuranoysl chloride (5) furnishes the regioisomeric N-1-beta-D-2'-deoxyribonucleosides 6a and 6b together with the dehalogenated N-2-regioisomers 8a and 8b, stereoselectively. The dehalogenation takes place after the glycosylation and results from the sensitivity of the N-2 nucleosides toward aqueous base. An addition/elimination mechanism is suggested for the dehalogenation reaction.