Facile access to the ABC ring system of the taxane diterpenes via anionic oxy-Cope rearrangements
作者:S.F. Martin、J.-M. Assercq、R.E. Austin、A.P. Dantanarayana、J.R. Fishpaugh、C. Gluchowski、D.E. Guinn、M. Hartmann、T. Tanaka、R. Wagner、J.B. White
DOI:10.1016/0040-4020(95)00095-p
日期:1995.3
functionalized by introducing a double bond conjugated to the carbonyl group (27a→40); moreover, oxygen functionality at C(13) could be introduced by allylic oxidation (28a→41 and 40→42). The enolates produced in situ by the anionic oxy-Cope rearrangement could be trapped by alkylating agents. These alkylations were highly stereoselective when the ketone enolate was trisubstituted as exemplified by
双环[2.2.2]辛二烯醇的阴离子氧基-Cope重排是构建取代的双环[5.3.1]十一碳烯酮的关键步骤,并为紫杉烷二萜的AB环系统提供了新的途径。对双环[2.2.2]辛二烯醇11a-e进行了阴离子加速的[3,3]-σ重排,得到双环[5.3.1]十一碳烯酮14a-e。还发现这种重组在取代度更高的系统中进行,如转化27a-c→28a-c ,30→32和31→33所证明。这些双环[5.3.1]十一碳烯酮通过引入与羰基共轭的双键(27a→40 )进一步官能化。此外,C(13)处的氧官能度可通过烯丙基氧化引入(28a→41和40→42 )。阴离子氧基-Cope重排原位产生的烯醇化物可能被烷基化剂捕获。当酮烯醇酸酯被三取代时,这些烷基化是高度立体选择性的,如反应44→47和45→48所示。紫杉烷二萜的这种进入允许通过将C环成环在AB环亚基上而进入紫杉烷的三环ABC构架,如序列30→49→50所示。