Studies towards the synthesis of (+)-ptilomycalin A; Stereoselective N-acyliminium ion coupling reactions to enantiopure C-2 substituted lactams

Abstract Highly stereoselective N -acyliminium ion coupling reactions of β-ketoester derived silyl enol ethers with enantiopure lactams derived from ( S )-malic acid are reported. This reaction type is applied in the synthesis of the enantiopure C-2 substituted lactam 27 , a plausible intermediate in a projected synthesis of ptilomycalin A.