Synthesis and analysis of the conformational preferences of 5-aminomethyloxazolidine-2,4-dione scaffolds: first examples of β(2)- and β(2, 2)-homo-Freidinger lactam analogues.

Constrained peptidomimetic scaffolds are of considerable interest for the design of therapeutically useful analogues of bioactive peptides. We present the single-step cyclization of (S)- or (R)-α-hydroxy-β(2)- or α-substituted-α-hydroxy-β(2, 2)-amino acids already incorporated within oligopeptides to 5-aminomethyl-oxazolidine-2,4-dione (Amo) rings. These scaffolds can be regarded as unprecedented β(2)- or β(2, 2)-homo-Freidinger lactam analogues, and can be equipped with a proteinogenic side chain at each residue. In a biomimetic environment, Amo rings act as inducers of extended, semi-bent or folded geometries, depending on the relative stereochemistry and the presence of α-substituents.