Total Synthesis of Avermectin B1a: Final Coupling Reactions and the Total Synthesis of Avermectin B1a Aglycone

Abstract

Synthesis of the avermectin B1a aglycone (3) involving sulphone stabilised anion coupling of a C1-C10 fragment 1 with C11-C25 spiroacetal portion 2 is described. The synthesis exploits chemoselectivity in an effort to minimise the need for functional group protection.