The (−)-enantiomer, ent-3, of the natural product (+)-cladospolide C (3) has been prepared for the first time using the monochiral cis-1,2-dihydrocatechol 5 as starting material. Key steps include coupling of the derived acid 6 with the enzymatically generated (S)-(+)-4-penten-2-ol (7) and ring-closing metathesis (RCM) of the resultant doubly unsaturated ester 8 to give lactone 9. The structure of this last compound has been confirmed by single-crystal X-ray analysis. This work has established that the absolute configuration of (+)-cladospolide C has been correctly assigned and is as illustrated in structure 3.
以单手性顺式-1,2-二氢邻苯二酚 5 为起始原料,首次制备了天然产物 (+)-cladospolide C (3) 的 (-)- 对映异构体 ent-3。关键步骤包括将衍生的酸 6 与酶法生成的 (S)-(+)-4- 戊烯-2-醇 (7) 进行偶联,并对生成的双不饱和酯 8 进行闭环偏析 (RCM),从而得到内酯 9。最后一种化合物的结构已通过单晶 X 射线分析得到证实。这项工作确定了 (+)-cladospolide C 的绝对构型,如结构 3 所示。