Synthesis and Conformational Study of Chiral Oxepines: The Baylis−Hillman Reaction and RCM Approach with Sugar Aldehyde
作者:Vrushali H. Jadhav、Omprakash P. Bande、Rahul V. Pinjari、Shridhar P. Gejji、Vedavati G. Puranik、Dilip D. Dhavale
DOI:10.1021/jo900660q
日期:2009.9.4
The Baylis−Hillman reaction of 3-O-allyl-α-d-xylo-pentodialdo-1,4-furanose 3 afforded a diastereomeric mixture of d-gluco- and l-ido-configured α-methylene-β-hydroxy esters 4a and 4b, respectively, in a ratio of 2:3. Reduction of the ester functionality in 4a/4b gave alcohols 5a/5b. The diene thus formed in 5a/5b was subjected to ring-closing metathesis (Grubbs' second-generation catalyst) to afford
3-的的Baylis-Hillman反应ø -烯丙基-α- d -木糖-pentodialdo -1,4-呋喃糖3得到的非对映体混合物d -gluco-和升-ido配置的α亚甲基β羟基酯4a中和4b分别以2:3的比例。降低4a / 4b中的酯官能度得到醇5a / 5b。将如此在5a / 5b中形成的二烯进行闭环复分解(Grubbs的第二代催化剂),得到氧杂双环系统6a / 6b高产。进一步操纵6a和6b中的丙酮化物官能度,分别得到了新的多羟基化的oxepines 1a / 2a和1b / 2b。oxepines 1a和1b在D 2 O中的1 H NMR显示信号加倍,表明它们存在于两个不同的旋转异构体/构象异构体中。通过使用密度泛函理论计算1和2构象异构体的能量,并将计算出的1 H NMR化学位移图与实验光谱图相关联,可以证实这一事实。