Synthesis of 7-Halogenated 8-Aza-7-deaza-2′-deoxyguanosines and Related Pyrazolo[3,4-d]pyrimidine 2′-Deoxyribonucleosides
作者:Frank Seela、Georg Becher
DOI:10.1055/s-1998-4483
日期:1998.2
The synthesis of 7-bromo and 7-iodo derivatives of 8-aza-7-deaza-2′-deoxyguanosine (2, 3) as well as the halogenated 4-alkoxy derivatives 4 a - c and 5 a - c is described. Glycosylation of the halogenated pyrazolo[3,4-d]pyrimidine anions of 7 a -c or 8 a - c with 2-deoxy-3,5-di-O-(p-toluoyl)-α-d-erythro-pentofuranosyl chloride (9) yields regioisomeric glycosylation products, the N(1)-isomers 10 a - c and 11 a - c as well as the N(2)-compounds 12 a - c. The latter isomers lose their halogen during the glycosylation in the presence of non-anhydrous KOH. Anhydrous conditions (NaH) furnished 10 c, 11 c together with the halogenated N(2)-isomers 13 a,b. Compounds 10 a - c, and 11 a - c were deprotected and converted to the 4-alkoxy nucleosides 4 a - c and 5 a - c. The N(1)-nucleosides 4 c and 5 c were hydrolyzed to give the 7-bromo or 7-iodo derivatives of 8-aza-7-deaza-2′-deoxyguanosines 2 and 3. Different from regular 2′-deoxyribonucleosides the sugar moiety of pyrazolo[3,4-d]pyrimidine 2′-deoxyribonucleosides shows a preferred N-type pucker (3T2) in solution, a conformation which is also detected in the solid state.
描述了8-氮杂-7-脱氮-2′-去氧鸟苷(2, 3)的7-溴和7-碘衍生物的合成,以及卤化的4-烷氧基衍生物4a-c和5a-c。将7a-c或8a-c的卤化吡唑[3,4-d]嘧啶阴离子与2-去氧-3,5-二-O-(对甲苯酰基)-α-d-赤糖善氟糖氯化物(9)进行糖苷化反应,得到区域异构糖苷化产物,N(1)-异构体10a-c和11a-c,以及N(2)-化合物12a-c。后者异构体在无水氢氧化钾存在下糖苷化时失去卤素。在无水条件下(氢化钠)生成了10c、11c以及卤化的N(2)-异构体13a,b。化合物10a-c和11a-c被去保护并转化为4-烷氧基核糖苷4a-c和5a-c。N(1)-核糖苷4c和5c被水解,得到8-氮杂-7-脱氮-2′-去氧鸟苷的7-溴或7-碘衍生物2和3。与常规的2′-去氧核糖核苷不同,吡唑[3,4-d]嘧啶2′-去氧核糖核苷的糖部分在溶液中显示出优先的N型扭曲(3T2),这种构象在固态中也得到了验证。