Direct asymmetric α-allylation of α-branched aldehydes by two catalytic systems with an achiral Pd complex and a chiral primary α-amino acid.

Direct α-allylation of α-branched aldehydes was successfully carried out with a readily available allyl ester by combined use of two catalytic systems: Tsuji-Trost allylation reaction with an achiral palladium complex and enamine catalysis with a chiral primary α-amino acid. A quaternary carbon stereogenic center was constructed stereoselectively to give various 2,2-disubstituted pent-4-enals in good yields with high enantioselectivity.

Enantioselective synthesis of gabapentin analogues via organocatalytic asymmetric Michael addition of α-branched aldehydes to ß-nitroacrylates.

Michael addition reaction of α-branched aldehydes to ß-nitroacrylates was successfully carried out by using a mixed catalyst consisting of a primary amino acid, L-phenylalanine, and its lithium salt to give ß-formyl-ß'-nitroesters having a quaternary carbon centre in good yields (up to 85%) with high enantioselectivity (up to 98% ee). By using benzyl ß-nitroacrylates as Michael acceptors, the obtained ß-formyl-ß'-nitroesters were converted into various 4,4-disubstituted pyrrolidine-3-carboxylic acids including analogues of gabapentin (Neurotin(®)) in one step from the Michael adducts in high yields.