Deprotonation of 2-benzenesulphonyltetrahydropyrans with n-butyllithium affords anions which react with substituted epoxides to give spiroketals upon acidification. Using this approach a highly convergent synthesis of the C-11 to C-25 fragment of the milbemycins was achieved.
用
正丁基锂对2-苯磺酰基
四氢吡喃进行质子化反应,得到的阴离子可与取代的
环氧化物反应,在酸化时可得到螺
缩酮。使用这种方法,实现了米尔贝霉素的C-11至C-25片段的高度收敛合成。