A diastereocontrolled synthesis of the spiroketal sub-unit of 22,23-dihydroavermectin B1b has been developed using a formal double condensation at both ends of pentane 2,4-dione with intermediate formation of the ketal .
利用戊烷2,4-二酮的戊端的正式双缩合和缩酮的中间形成,开发了非对映体合成的22,23-dihydroavermectin B 1b的spiroketal亚基。
Enantioselective synthesis of the spiroketal unit of milbemycins and 22,23-dihydroavermectins
The crystalline spiroketal sub-unit has been synthesized in ten steps from the 2S,3R-diol using a remote partial stereocontrol for the aldolisation step.