Structure and Synthesis of 6-(Substituted-imidazol-1-yl)purines: Versatile Substrates for Regiospecific Alkylation and Glycosylation at N91
摘要:
X-ray crystal structures of several 6-(azolyl) purine base and nucleoside derivatives show essentially coplanar conformations of the purine and appended 6-(azolyl) rings. However, the planes of the purine and imidazole rings are twisted similar to 57 degrees in a 2-chloro-6-(4,5-diphenylimidazol-1-yl) purine nucleoside, and a twist angle of similar to 61 degrees was measured between the planes of the purine and pyrrole rings in the structure of a 6-(2,5-dimethylpyrrol-1-yl) purine nucleoside derivative. Shielding "above" N7 of the purine ring by a proximal C-H on the 6-azolyl moiety is apparent with the coplanar compounds, but this effect is diminished in those without coplanarity. Syntheses of 6-(azolyl)purines from both base and nucleoside starting materials are described. Treatment of 2,6- dichloropurine with imidazole gave 2-chloro-6-(imidazol)-yl)purine. Modified Appel reactions at C6 of trityl-protected hypoxanthine and guanine derivatives followed by detritylation gave 6-(imidazol-1-yl)- and 2-amino-6-(imidazol-1-yl) purines. Imidazole was introduced at C6 of 2',3',5'-tri-O-acetylinosine by a modified Appel reaction, and solvolysis of the glycosyl linkage gave 6-(imidazol-1-yl) purine. Guanosine triacetate was transformed into the protected 2,6-dichloropurine nucleoside, which was subjected to SNAr displacement with imidazoles at C6 followed by glycosyl solvolysis to provide 2-chloro-6-(substituted-imidazol-1-yl) purines. Potential applications of these purine derivatives are outlined.
Structure and Synthesis of 6-(Substituted-imidazol-1-yl)purines: Versatile Substrates for Regiospecific Alkylation and Glycosylation at N9<sup>1</sup>
作者:Minghong Zhong、Ireneusz Nowak、John F. Cannon、Morris J. Robins
DOI:10.1021/jo060340o
日期:2006.5.1
X-ray crystal structures of several 6-(azolyl) purine base and nucleoside derivatives show essentially coplanar conformations of the purine and appended 6-(azolyl) rings. However, the planes of the purine and imidazole rings are twisted similar to 57 degrees in a 2-chloro-6-(4,5-diphenylimidazol-1-yl) purine nucleoside, and a twist angle of similar to 61 degrees was measured between the planes of the purine and pyrrole rings in the structure of a 6-(2,5-dimethylpyrrol-1-yl) purine nucleoside derivative. Shielding "above" N7 of the purine ring by a proximal C-H on the 6-azolyl moiety is apparent with the coplanar compounds, but this effect is diminished in those without coplanarity. Syntheses of 6-(azolyl)purines from both base and nucleoside starting materials are described. Treatment of 2,6- dichloropurine with imidazole gave 2-chloro-6-(imidazol)-yl)purine. Modified Appel reactions at C6 of trityl-protected hypoxanthine and guanine derivatives followed by detritylation gave 6-(imidazol-1-yl)- and 2-amino-6-(imidazol-1-yl) purines. Imidazole was introduced at C6 of 2',3',5'-tri-O-acetylinosine by a modified Appel reaction, and solvolysis of the glycosyl linkage gave 6-(imidazol-1-yl) purine. Guanosine triacetate was transformed into the protected 2,6-dichloropurine nucleoside, which was subjected to SNAr displacement with imidazoles at C6 followed by glycosyl solvolysis to provide 2-chloro-6-(substituted-imidazol-1-yl) purines. Potential applications of these purine derivatives are outlined.
Regiospecific and Highly Stereoselective Coupling of 6-(Substituted-imidazol-1-yl)purines with 2-Deoxy-3,5-di-<i>O</i>-(<i>p</i>-toluoyl)-α-<scp>d</scp>-<i>e</i><i>rythro</i>-pentofuranosyl Chloride. Sodium-Salt Glycosylation in Binary Solvent Mixtures: Improved Synthesis of Cladribine<sup>1</sup>
作者:Minghong Zhong、Ireneusz Nowak、Morris J. Robins
DOI:10.1021/jo061282+
日期:2006.9.1
also diminishes the extent of anomerization of the chlorosugar. Stirred reaction mixtures of the modified-purine sodium salts generated in a polar solvent and cooled solutions of the protected 2-deoxysugar chloride in a nonpolar solvent give 2‘-deoxynucleoside derivatives with N9 regiochemistry and enhanced β/α configuration ratios. Application of the binary-solvent methodology with 2-chloro-6-(su
的6-(取代咪唑-1-基)嘌呤钠盐的糖基化与2-脱氧-3,5-二- Ö - (p甲苯甲酰)-α- d -赤-戊呋喃糖酰氯继续进行N9异构体的区域特异性形成。在C6连接的咪唑部分上具有亲脂性取代基的基础底物更易溶于有机溶剂,并且通过二元溶剂混合物可进一步提高溶解度。选择性溶剂化也减少了氯糖的异构化程度。在极性溶剂中生成的改性嘌呤钠盐的搅拌反应混合物与受保护的2-脱氧糖氯化物在非极性溶剂中的冷却溶液的搅拌反应产生具有N9区域化学作用和增强的β/α构型比的2'-脱氧核苷衍生物。在冷乙腈中使用2-氯-6-(取代的咪唑-1-基)嘌呤盐和在冷二氯甲烷中使用氯糖的二元溶剂方法的应用,可得出定量定量的β-异头2'-脱氧核苷N9异构体的收率中间体。直接氨解(NH此类中间体的3 / MeOH)或咪唑环的苄基化反应,然后咪唑鎓盐的轻度氨解产生了临床抗癌药物克拉屈滨(2-chloro-2'-deoxyadenosine)的高收率。