Synthesis of [13]-membered macrocyclic stevastelins via a transesterification reaction as the key step: total synthesis of stevastelin C3

A new synthesis of stevastelin C3 (3), a 13]-membered ring component of the stevastelin family, whose structure was recently revised, is reported. Initially, a macrolactonization approach was attempted to generate the 13]-membered macrolactone but this met with failure, so a translactonization reaction was tried to obtain the targeted stevastelin C3 (3) from the corresponding 15]-membered ring counterpart. Unfortunately, this strategy did not prove successful, and, consequently, we opted to undertake a transesterification reaction from 23, as a means to accommodate the requisite aminoacid moiety at the correct position, to obtain 24. From 24, and through intermediates 25-28, the acyclic precursor of the 13]-membered ring macrolactone, compound 30, was efficiently prepared. By utilizing the synthetic course developed by Chida, we took 30 forward and completed the total synthesis of stevastelin C3 (3).