Synthesis of the Spin-labelled beta-Amino Acids cis- and trans-beta- TOAC, and a Preliminary Conformational Study of trans-beta-TOAC/trans-ACHC Peptides

摘要

The nitroxide-bearing, achiral, cyclic, C~(alpha)-tetrasubstituted alpha-amino acid residue TOAC has been widely used to label conformationally restricted alpha-peptides at TV-terminal and/or internal positions for biological studies or 3D-structural investigations involving intramolecular spin-spin interactions (ESR). We have been interested in the spin-labelled, chiral, cyclic beta-amino acids cis-beta-TOAC and trans-beta-TOAC, that could be used for the structural investigation of helical (3-peptides. Herein, we report the synthesis of the cis-/trans-beta-TOAC amino acids in an enantiomerically pure form, as well as the synthesis and a preliminary conformational study of terminally protected trans-beta-TOAC/trans-ACHC (2-aminocyclohexane carboxylic acid) peptides.