Enyne versus diene RCM in the synthesis of cyclopentene derivatives toward the A ring of FR182877

Abstract : The A ring of FR182877, exemplified by ent-4-b,c, has been synthesized, involving an enyne RCM as the key step. A systematic comparison of enyne vs diene RCM for the formation of cyclopentene derivatives showed that the latter metathesis proceeds much more easily even for this ring size.