Diastereoselective synthesis of the 19-epi-C18–C25 segment of (−)-lasonolide A and an unusual inversion at C19

Diastereoselective construction of the 19-epi-C18–C25 segment of (−)-lasonolide A was achieved using a 5-exo-trigonal mode of radical cyclization for the creation of the contiguous quaternary and tertiary stereogenic centers at C22 and C23 as the key reaction step. During the dehydration stage, it was found that an unusual inversion of configuration took place.