Peter Wipf

3-Amino-2H-azirines in the synthesis of peptides: : Tetrapeptides with α,α-disubstituted α-amino acids

Abstract 3-Amino-2,2-dialkyl-2H-azirines 1 are synthons for α,α-disubstituted α-amino acids. Tetrapeptides 15 , containing two such amino acids, were synthesized in high yield by application of the “azirine/oxazolone-method”. In this versatile approach for the incorporation of disubstituted amino acids into the peptide chain, N-protected amino acids or peptides are coupled with 3-amino-2H-azirines 1 . After selective hydrolysis of the newly formed C-terminal amide, condensation with valine-benzylester was achieved via in situ generated oxazole-5 (4H)-ones in the presence of hydroxybenzotriazole. The conformational properties of tetrapeptides 15 are discussed on the basis of NMR- and CD-spectra. It is shown that α,α-disubstitution favours the formation of β-turns even in very short oligopeptides. The “azirine/oxazolone-method” offers an efficient strategy for the synthesis of peptide-models used for conformational studies.

Synthese von 4-arylthio-3-oxazolin-5-onen

Abstract 4-Arylthio-3-oxazolin-5-ones have been synthesized in a ‘one pot reaction’ from ethyl cyanoformate, thiophenols and ketones in the presence of diethylamine and titanium tetrachloride.