5-<i>Exo</i> versus 6-<i>Endo</i> Cyclization of Nucleoside 2-Sila-5-hexenyl Radicals: Reaction of 6-(Bromomethyl)dimethylsilyl 1‘,2‘-Unsaturated Uridines
作者:Junko Ogamino、Hideaki Mizunuma、Hiroki Kumamoto、Shingo Takeda、Kazuhiro Haraguchi、Kazuo T. Nakamura、Hiroshi Sugiyama、Hiromichi Tanaka
DOI:10.1021/jo040260p
日期:2005.3.1
The mode of cyclization of 2-sila-5-hexen-1-yl radicals generated from 6-(bromomethyl)dimethylsilyl-1‘,2‘-unsaturated uridines was investigated. In contrast to the case of the 2‘-unsubstituted 6-silicon-tethered substrate (4), which undergoes exclusive 6-endo-cyclization, reactions of the 2‘-substituted (Me, CO2Me, OBz, and Cl) derivatives (14, 20, 22, and 24) uniformly proceeded in preferential or
研究了由6-(溴甲基)二甲基甲硅烷基-1',2'-不饱和尿苷生成的2-sila-5-hexen-1-yl自由基的环化模式。与此相反的2'-取代的6- -硅-拴系的底物(的情况4),其经历独家6-内切-cyclization,2'-取代的(Me中,CO的反应2 Me中,OBZ和Cl)衍生物(14,20,22,和24)中优先或独家5-均匀地进行外切-mode。还对所得环化产物进行了Tamoo氧化,以合成相应的1'- C-羟甲基衍生物。