Synthesis and Transformation of (-)-Isopulegol-Based Chiral β-Aminolactones and β-Aminoamides.

A library of isopulegol-based β-amino acid derivatives has been developed from commercially-available (-)-isopulegol. Michael addition of primary and secondary amines towards α,β-unsaturated γ-lactones was accomplished resulting in β-aminolactones in highly-stereoselective reactions. Ring-opening of β-aminolactones with different amines furnished excellent yields of β-aminoamides. Moreover, the applicability of aminolactones in peptide synthesis was examined by opening the lactone ring with α- and β-aminoesters, providing dipeptides as promising chiral substrates for the synthesis of foldamers. The antiproliferative activities of β-aminolactones and β-aminoamides were explored, and the structure-activity relationships were studied from the aspects of the stereochemistry of the monoterpene ring and the substituent effects on the β-aminoamide ring system. The N-unsubstituted (-)-isopulegol-based β-aminoamides exhibited considerable antiproliferative activity against a panel of human adherent cancer cell lines (HeLa, MCF7 and MDA-MB-231).