Stereoselective routes to substituted β-amino carbonyl compounds via heterodiene cycloadditions of an auxiliary-based C2-symmetric ketene acetal

Heterodiene cycloadditions of (S,S)-4,5-bis(o-tolyl)-2-methylene-1,3-dioxolane 1 with a series of substituted β-amido-α,β-unsaturated carbonyl compounds are diastereoselective (dr ≥4:1). The cycloadducts from N-(2-(1-oxoethyl)-3-oxobut-1-enyl)ethanamide 2a can be purified by crystallisation and hydrolysed with acid to generate the corresponding β-amidoacetic esters, the sequence providing an auxiliary-based stereoselective route to such compounds.