which was critical for suppressing elimination of the activated allylic alcohol.
Interestingly, the (S)-allylic alcohol of compound 246 yielded only 5 % of the
desired lactone 247 under modified Boden–Keck [114] conditions (EDC 218, PPh 3 ,
DMAP, DMAP∙TsOH, THF).
Scheme 71 The Mitsunobu protocol in the total syntheses of combretastatin D-1, 244 and
combretastatin D-2, 245
Scheme 72 The Mitsunobu protocol in the total synthesis of FR-901,228, 248
Synthesis of 12- to 16-Membered-Ring Lactones
423
Interestingly, the (S)-allylic alcohol of compound 246 yielded only 5 % of the
desired lactone 247 under modified Boden–Keck [114] conditions (EDC 218, PPh 3 ,
DMAP, DMAP∙TsOH, THF).
Scheme 71 The Mitsunobu protocol in the total syntheses of combretastatin D-1, 244 and
combretastatin D-2, 245
Scheme 72 The Mitsunobu protocol in the total synthesis of FR-901,228, 248
Synthesis of 12- to 16-Membered-Ring Lactones
423