A directed aldol approach to (+)-milbemycin β₃

Abstract

Key steps in a total synthesis of (+)-milbemycin β3are the construction of the 1,7-dioxaspiro[5.5]undecane (10) by a Lewis acid-catalysed intramolecular directed aldol reaction and the use of sulphone-based olefination reactions for the construction of the double bonds at C(10)–C(11) and C(14)–C(15)