Nucleosides and Nucleotides. 184. Synthesis and Conformational Investigation of Anti-Fixed 3-Deaza-3-halopurine Ribonucleosides<sup>1</sup><sup>,</sup><sup>2</sup>
作者:Noriaki Minakawa、Naoshi Kojima、Akira Matsuda
DOI:10.1021/jo990638x
日期:1999.9.1
A versatile synthetic route to 3-deaza-3-haloinosines 6-8 and 46, -adenosines 15-17 and 64, and -guanosines 25, 26, and 52 is described. 3-Deaza-3-chloro-, -bromo-, and -iodopurine ribonucleosides can be synthesized by treating the 3-deazapurine ribonucleosides with N-halosuccinimides. For the synthesis of 3-deaza-3-fluoropurine ribonucleosides, 5-formylimidazole-4-carboxamide ribosides 34 and 35 prepared from 5-iodoimidazole-4-carboxamide derivatives 29 and 31 were us ed as the key intermediates. The reaction of 34 and 35 with lithium (trimethylsilyl)acetylide and sodium cyanide, respectively, followed by appropriate manipulations gave 3-deaza-3-fluoroinosine derivative 46 and 3-deaza-3-fluoroguanosine derivative 52. 3-Deaza-3-fluoroadenosine (64) was also synthesized by selective reductive deamination of 4,6-diamino-7-fluoroimidazo[4,5-c]pyridine derivative 51, followed by deprotection. A conformational analysis using H-1 NMR and NOE experiments showed that the introduction of halogens (chloro, bromo, and iodo) into the 3-position of 3-deazapurine ribonucleosides forced fixation of the glycosyl torsion angle in the anti region, but did not-abnormally influence sugar puckering. On the other hand, 3-deaza-3-fluoropurine ribonucleosides should rotate freely around the glycosyl bond.