Titanium Tetrachloride-Mediated Diels-Alder Reactions of Cyclopentadiene with Di-l-menthyl Methylenemalonate and Its Acetoxy Derivative as New Chiral Dienophiles for Asymmetric Induction

Abstract

Asymmetric synthesis of [1S, 2S, 3R, 4R]-2, 3-dihydroxy-4-hydroxymethylcyclopent-1-ylmalonate (its racemic form is already known as a versatile building block for carbocyclic C-nucleosides) was achieved by Diels-Alder reaction of cyclopentadiene with di-l-menthyl acetoxymethylenemalonate, followed by retrograde aldol C-C bond fission under reductive conditions. Asymmetric induction in Diels-Alder reactions using the chiral dienophile and its nor-acetoxy derivative is discussed from a mechanistic viewpoint and a new concept for asymmetric induction is proposed.