Unexpected Dehalogenation of 3-Bromopyrazolo[3,4-d]pyrimidine Nucleosides During Nucleobase-Anion Glycosylation |
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| Authors: | Frank Seela Matthias Zulauf Georg Becher |
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| Institution: | Laboratorium für Organische und Bioorganische Chemie , Institut für Chemie, Universitat Osnabruck , Barbarastr. 7, D-49069 , Osnabrück , Germany |
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| Abstract: | Abstract The anion-glycosylation (KOH, MeCN, TDA-1) of 3-bromopyrazolo3,4-d]-pyrimidines 4a and 4b with 2-deoxy-3,5-di-O-(p-toluoyl)-α-D-erythro-pentofuranosyl chloride (5) furnishes the regioisomeric N′-β-D-2′-deoxyribonucleosides 6a and 6b together with the dehalogenated N2-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. |
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