Zusammenfassung
A straightforward synthesis of (S)- and (R)-N-Boc-5-oxopiperazine-2-carboxylic acid is reported starting from L- or D-serine and ethyl glyoxylate. Those were evaluated as constituents in two tetrapeptides by studying their secondary Structure by H-1 NMR spectroscopy. In the case of Boc-Val-(S)-PCA-Gly-Leu-OMe, two readily interconverting conformations (in a 40%: 60% ratio) were observed, ...
Zusammenfassung
A straightforward synthesis of (S)- and (R)-N-Boc-5-oxopiperazine-2-carboxylic acid is reported starting from L- or D-serine and ethyl glyoxylate. Those were evaluated as constituents in two tetrapeptides by studying their secondary Structure by H-1 NMR spectroscopy. In the case of Boc-Val-(S)-PCA-Gly-Leu-OMe, two readily interconverting conformations (in a 40%: 60% ratio) were observed, differing for the cis-trans isomerizaton of the tertiary amide bond, while Boc-Val-(R)-PCA-Gly-Lcu-OMe displayed an equilibrium between a gamma-turn and it type II beta-turn conformation.
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