Facile Preparation of (±)-12-Epiprostaglandins from 7-Oxabicyclo[2.2.1]hept-5-en-2-one<i>via</i>an all-<i>cis</i>-formyllactone related to<i>Corey</i>lactone
作者:Jean-Paul Vionnet、Philippe Renaud
DOI:10.1002/hlca.19940770710
日期:1994.11.2
The bicyclic monoselenoacetal 7, easily obtained from (±)-7-oxabicyclo[2.2.1]hept-5-en-2-one (6) via a radical addition-acyl migration sequence, was converted to racemic 12-epiprostaglandins 3 and 4. The key intermediate was the all-cis-formyllactone 2b related to Corey lactone (see 12; Scheme 1). The presence of a (tert-butyl)-dimethylsilyl protective group for the 11-OH substituent (prostaglandin
容易地从(±)-7- oxabicyclo [2.2.1] hept-5-en-2-one(6)通过自由基加成酰基迁移序列获得的双环单硒缩醛7转化为外消旋的12-表塔格列汀3和4。关键中间体是与Corey内酯有关的全顺式-甲酰基内酯2b(参见12;方案1)。发现在11-OH取代基上存在(叔丁基)-二甲基甲硅烷基保护基(前列腺素编号)对于在Wittig - Horner期间避免β-消除和差向异构化至关重要反应(方案2)。在甲酰内酯阶段在C(12)上进行差向异构化(参见2b)也是可能的,并且可以得到天然存在的前列腺素和类似物的已知前体1b。