Journal of the American Chemical Society p. 8598 - 8609 (1989)
Update date:2022-07-29
Topics:
Albrecht-Gary, A. M.
Blanc-Parasote, S.
Boyd, D. W.
Dauphin, G.
Jeminet, G.
et al.
X-14885A is an open-chain carboxylic ionophore, recently isolated from a Streptomyces strain.NMR data have shown that the free acid form adopts a pseudocyclic conformation in chloroform, while in the neutral A2Mg complex a rotation of the benzoxazole arm is achieved to accommodate the cation in a sandwich system.The replacement of the -NHMe by an -OH function and of a methyl group by H in position 15 for X-14885A does not lead to a large modification in the conformation of the new microbial metabolite in solution.The acid-base equilibria and the thermodynamics of association with alkali and alkali-earth cations are determined in methanol, from potentiometric and spectrophotometric measurements.Divalent cations M(2+) form strong complexes of 1:1 (AM(1+)) and 2:1 (A2M) stoichiometries, following the sequence Ca(2+) > Mg(2+) > Sr(2+) > Ba(2+).For AM(1+) + A(1-) <==> A2M, log KA2M are, respectively, 8.0, 7.3, 6.9, and 6.2 (I=0).A complete kinetic study is carried out in methanol for the A2Mg and A2Ca complexes, with use of a stopped-flow system.This work shows that the rate-limiting steps of the formation and dissociation mechanisms are associated with the charged complex AM(1+), the addition or loss of the second ligand being faster.As for the closely related ionophore A-23187 (calcimycin), the selectivity calcium/magnesium has predominantly a kinetic origin, with faster formation and dissociation rates of calcium complexes.The replacement of the -NHMe group in calcimycin by an -OH group in X-14885A has a drastic effect in the acid-base properties of X-14885A and on the acid-catalyzed dissociation pathway of its complexes.
View MoreJIANGXI ZHANGFENG CHEMICAL CO., LTD.
Contact:+86-0799-3413066
Address:Xiyuan village, Xiabu Town, Xiangdong District
website:http://www.gihichemicals.com
Contact:+86-571-86217390
Address:No.567 Dengcai Street,Sandun,Westlake District,Hangzhou310030,Zhejiang,China.
Guangzhou PI & PI Biotech Inc. Ltd.
Contact:+86-20-81716320
Address:Suite 501,198 Kaiyuan Ave.,Science City, Guangzhou,China
SuZhou Hua-Emy Chemical Import and Export Co., LTD.
Contact:+86-512-88804994; +86-512-88804550;
Address:710, Building B, International Trade Center, 12 Huanghelu, Changshu, Jiangsu,China
Jiaxing Trustworthy Import And Export Co.,Ltd
Contact:+86-573-82030555
Address:Room 1202, Unit B, Charming plaza,No.1558 East Zhongshan Road , Jiaxing City, Zhejiang Province, China.
Doi:10.1002/jps.2600711105
(1982)Doi:10.1021/ja021224f
(2003)Doi:10.1080/10426507.2013.789878
(2014)Doi:10.1055/s-2004-835658
(2004)Doi:10.1007/BF00503180
(1982)Doi:10.1080/00397919508011406
(1995)