Studies towards the synthesis of neopeltolide: synthesis of a ring-closing metathesis macrocyclization precursor

An advanced ring-closing metathesis precursor for the synthesis of the marine macrolide neopeltolide is prepared in a stereocontrolled manner by the coupling of the C2–C10 and C11–C16 subunits. The metathesis reaction of 4 with Grubbs’ II or Nolan’s indenylidene catalyst led to the unexpected formation of cycloheptene 18.