The reduction of N-hydroxy-α-imino esters with Zn–MsOH in THF afforded α-amino esters in high yields. The reduction of N-hydroxy-α-iminocarbonyl-oligopeptide methylesters prepared from l-phenylalanine and l-leucine di-, tri-, tetrapeptides gave the corresponding S-formed oligopeptide methylesters in moderate diastereoselectivities.
Correlation between the Configurational Structure and the Asymmetric Hydrogenation of Δ<sup>1</sup>-, Δ<sup>2</sup>-, and Δ<sup>3</sup>-Dehydrotripeptides
The heterogeneous catalytic hydrogenation of Δ1 -dehydrotripeptides (Δ1 -DHP), which have a β-turn structure, was carried out to give the corresponding tripeptides indicative of the very large diastereomeric excess, comparing with those from Δ2- and Δ3 -DHPs. The efficient differences of the chiral inductions were found to be closely correlated to the configuration of the respective DHPs.