3 + 2]-annulation reactions of chiral allylsilanes and chiral aldehydes. studies on the synthesis of bis-tetrahydrofuran substructures of annonaceous acetogenins

Structure: See text] Double asymmetric 3 + 2]-annulation reactions of chiral beta-silyloxyallylsilanes with chiral 2-tetrahydrofuranyl carboxaldehydes have been studied, leading to the stereocontrolled synthesis of six diastereomeric bis-tetrahydrofuran structures corresponding to the core subunits of members of the Annonaceous acetogenin family of natural products. Transition-state models are proposed to account for the stereoselectivity of the double-stereodifferentiating 3 + 2]-annulation reactions.