NMR-based quantitative studies of the conformational equilibrium between their square and folded forms of ascidiacyclamide and its analogues.

ABSTRACT: Ascidiacyclamide [cyclo(-Ile^1,5-oxazoline^2,6-D-Val^3,7-thiazole^4,8-)] (1) is a cytotoxic cyclic peptide from the ascidian, or sea squirt. Through structural analyses using asymmetric analogues [Xxx¹: Ala (2), Val (3), Leu (4), Phe (5), cyclohexylalanine (6) and phenylglycine (7)], we previously showed 1 to exist in a conformational equilibrium between square and folded forms. In the present study, five new asymmetric analogues [Xxx¹: 2-aminobutyric acid (8), 2-aminopentyric acid (9), tert-butylalanine (10), cyclohexylglycine (11) and tert-leucine (12)] were synthesized, and their structures were analyzed with X-ray diffraction and CD spectral measurements. Variable temperature ¹H NMR measurements were

SUBMITTER: Asano A 

PROVIDER: S-EPMC9056700 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature