Stereoselective Addition of a Wittig Reagent To Give a Single Nucleoside Oxaphosphetane Diastereoisomer. Synthesis of 2′(and 3′)-Deoxy-2′(and 3′)-methyleneuridine (and cytidine) Derivatives from Uridine Ketonucleosides
作者:Vicente Samano、Morris J. Robins
DOI:10.1055/s-1991-26774
日期:——
Treatment of 3′,5′(or 2′,5′)-bis-O-silyl-protected 2′(or 3′)-ketouridine derivatives with methyltriphenylphosphonium bromide and sodium 2-methyl-2-butoxide in diethyl ether/benzene at 0-4°C resulted in the slow formation of the corresponding 2′(or 3′)-deoxy-2′(or 3′)-methylene analogues. 1H- and 31P-NMR spectra were in harmony with formation of a single oxaphosphetane diastereoisomer during early stages of the Wittig reaction. Conversions of protected deoxymethyleneuridine to deoxymethylenecytidine derivatives were effected smoothly via 4-(1,2,4-triazol-1-yl) intermediates. Deprotection with tetrabutylammonium fluoride gave 2′(or 3′)-deoxy-2′(or 3′)-methyleneuridine and cytidine nucleosides.
在0-4°C下,将3′,5′(或2′,5′)-双-O-硅烷保护的2′(或3′)-酮尿苷衍生物与甲基三苯基膦溴化物和2-甲基-2-丁氧基钠在二乙醚/苯中反应,缓慢形成相应的2′(或3′)-脱氧-2′(或3′)-亚甲基类似物。1H和31P-NMR光谱在早期Wittig反应阶段显示形成单一的氧膦杂环丁烷非对映异构体。通过4-(1,2,4-三唑-1-基)中间体,保护的脱氧亚甲基尿苷顺利转化为脱氧亚甲基胞苷衍生物。用四丁基氟化铵进行脱保护得到2′(或3′)-脱氧-2′(或3′)-亚甲基尿苷和胞苷核苷。