龙脑烯醛同单重态氧反应的立体选择性

用竹红菌甲素匹配高压钠灯光敏氧化龙脑烯醛,高产率并有立体选择性地获得反应主产物,α-(2,2-二甲基-3-亚甲基-4-羟基-1-环戊烷基)乙醛。反应具有协同的“ene”反应特性。反应的立体选择性被龙脑烯醛的分子构象,取代基的空间位阻效应和烯丙基氢的轴向定位所控制。羰基同环戊烯基的相互隐蔽的分子构象对反应的立体选择性起关键作用。

STEREOSELECTIVITY OF THE REACTION OF CAMPHOLENIC ALDEHYDE WITH SINGLET OXYGEN

The stereoselective reaction was studied of ampholenic aldehyde with singlet oxygen which was produced by hypocrellin A as a sensitizer with a high pressure sodium lamp. An "ene" reaction process was postulated in accordance with the analysis of the products composition and distribution. The predominant product, α-(2,2-dimethyl-3-methylene-4-hydroxy-l-cyclopentayl) acetaldehyde, was formed stereoselectively as singlet oxygen attacked C₄-position of double bond of cyclopentenyl on Ⅲ-face. The control stereoselective factors include molecular conformation, steric hindrance of substituted methyl groups and the axil orientation of allylic hydrogen. The eclipsed conformation between carbonyl double bond and single bond of C₁-cyclo-pentenyl ring as a key factor was demonstrated.