title: A flat squared conformation of an ascidiacyclamide derivative caused by chiral modification of an oxazoline residue.
abstract: We designed a deoxazoline-ascidiacyclamide (dASC), cyclo(-L-Ile-L-allo-Thr-D-Val-thiazole-)(2), diastereomer having 10S, 11R, 37R, and 38S configurations ([SR,RS]dASC) and a corresponding product having 10S, 11S, 37R, and 38R configurations ([SS,RR]ASC) with the aim of understanding better the relationship between conformational behaviour and chirality. X-ray diffraction analysis revealed that [SR,RS]dASC is folded in a manner similar to other dASC analogues. By contrast, [SS,RR]ASC is a novel, flat conformer that is larger than the major square and folded ASC conformers and contains a cavity created by the flat peptide ring. In addition, [SS,RR]ASC retains approximately 60% of the cytotoxicity of the parent molecule.
authors.affiliation: Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 591-1094, Japan. asano@gly.oups.ac.jp
authors.forename: Akiko
authors.initials: A
authors.lastname: Asano
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamada
authors.forename: Atsushi
authors.initials: A
authors.lastname: Numata
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Katsuya
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sasaki
authors.forename: Taizo
authors.initials: T
authors.lastname: Taniguchi
authors.forename: Mitsunobu
authors.initials: M
authors.lastname: Doi
mesh_terms: D018360:Crystallography, X-Ray; D008968:Molecular Conformation; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D010456:Peptides, Cyclic; C467062:cyclo(isoleucyl-allo-threonyl-valyl-thiazole-isoleucyl-allo-threonyl-valyl-thiazole)