9 ジルコニウムを用いる立体選択的〔2,3〕-Wittig転位反応

抄録

Though [2,3]-Wittig rearrangement has recently been shown by Nakai et al, to be a useful method of stereocontrol, the same rearrangement of allyloxyacetic acid has been reported to proceed with rather poor selectivity. In the course of the studies directed to new stereocontrolled synthesis of hydroxy acids, we found that amides or esters of allyloxyacetic acids underwent the rearrangement in highly stereo-selective manner through zirconium mediation. Thus, the amides (5) bearing a chiral auxiliary rearranged to 3'-alkyl-2'-hydroxy amides (7) with high syn-diastereo and diastereoface selection, and the esters (10) to 11 with high syn-diastereo-selection. It is noteworthy that in the rearrangement of optically active 1'-alkyl-2'-butenyloxyacetic acids (12), exclusive (Z)-selection has been observed along with excellent syn-diastereo-selection and chirality transfer. The methods have been further applied to the synthesis of an alcohol (19) related to tedanolide, and to the synthesis of bombykol.