Reaction of meso-4-carbomethoxy-2-methylpentanal (1) with crotyltri-n-butyltin at −78°C in the presence of 1 eq BF3·OEt2, followed by the lactonization with BF3·OEt2, gave 6-(1-methylallyl)-3,4,5,6-tetrahydro-3,5-dimethyl-2-pyranone (2a) with the correct stereochemistry (erythro, anti-Cram) in 92% yield, which was converted to the title compound (3) in 85% yield upon the ozonolytic cleavage of the
在-1eq BF 3 ·OEt 2存在下,内消旋-4-羰甲氧基-
2-甲基戊醛(1)与
巴豆基三正
丁基锡在-78°C下反应,然后用BF 3 ·OEt 2内酯化,得到6 -(1-甲基烯丙基)-3,4,5,6-四氢-3,5-二甲基-2-
吡喃酮(2a)具有正确的立体
化学(赤型,抗Cram),收率92%,将其转化为
臭氧分解双键后,标题化合物(3)的产率为85%。