The C16-C36 unit of halichondrin B was stereoselectively synthesized via the aldol condensation of two C16-C26 esters with the previously synthesized C27-C36 aldehyde followed by E ring construction. The C16-C26 esters were prepared starting from (2S)-3-hydroxy-2-methylpropionic acid and L-tartaric acid via construction of the D ring by iodoetherification.
通过两个C16-C26酯与之前合成的C27-C36醛的醛醇缩合反应,继而构建E环,立体选择性地合成了halichondrin B的C16-C36单元。C16-C26酯是以(2S)-3-羟基-2-甲基
丙酸和
L-酒石酸为起始原料,通过
碘醚化构建D环制备而成。