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Ascidiacyclamides containing oxazoline and thiazole motifs assume square conformations and show high cytotoxicity
Author(s) -
Asano Akiko,
Yamada Takeshi,
Taniguchi Taizo,
Sasaki Masahiro,
Yoza Kenji,
Doi Mitsunobu
Publication year - 2018
Publication title -
journal of peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 66
eISSN - 1099-1387
pISSN - 1075-2617
DOI - 10.1002/psc.3120
Subject(s) - oxazoline , thiazole , cytotoxicity , stereochemistry , chemistry , terahertz radiation , ring (chemistry) , physics , in vitro , organic chemistry , optics , biochemistry , catalysis
Four cyclic octapeptides were designed from ascidiacyclamide [ cyclo (–Ile–Oxz– D ‐Val– Thz–) 2 ] (ASC, 1 ) to investigate the effects of oxazoline (Oxz) and thiazole (Thz) rings on the structures and cytotoxicities of the peptides. cyclo (–Ile–Thz– D ‐Val–Oxz–) 2 ( 2 ) had the same number of Oxz and Thz rings as ASC, but the ring positions were switched. cyclo (–Ile–Oxz– D ‐Val–Thz–Ile–Thz– D ‐Val–Thz–) ( 3 ) and cyclo (–Ile–Thz– D ‐Val–Oxz–Ile–Thz– D ‐Val–Thz–) ( 4 ) contained one Oxz and three Thz rings within the molecule. All Oxz rings were substituted with Thz in cyclo (–Ile–Thz– D ‐Val–Thz–) 2 ( 5 ). These analogues had new Oxz and Thz blocks forming the 24‐membered ring. Based on CD spectra and X‐ray diffraction analyses, the structures of all four analogues were classified as square ASC forms. But the structures of 2 and 5 differed from the original square form of 1 , and they showed no cytotoxicity. The structure of 3 was very similar to that of 1 , and 3 showed 10 times greater cytotoxicity than 1 . Although no definite structure of 4 was obtained, it showed three times greater cytotoxicity than 1 . It appears that the position and number of Oxz residues are essential determinants in the structure‐cytotoxicity relationship of ASC analogues.