Journal
JOURNAL OF ORGANIC CHEMISTRY
Volume 84, Issue 15, Pages 9684-9692Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.joc.9b01377
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Funding
- CNPq
- CAPES
- FAPESC
- CNPq/INCT-Catalise [465454/2017-3]
- Ministerio de Economia y Competitividad of Spain [CTQ2017-84354-P]
- Xunta de Galicia [GR 2007/085, IN607C 2016/03]
- Centro singular de investigation de Galicia accreditation (2016-2019) [ED431G/09]
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The study of host-guest complexation between reactive 2-carboxyphthalanilic acid (CPA) and two cationic pillararenes has been carried out. Host-guest complexation with significant kinetic effects was observed only with the smaller cavity size pillararene (P5A). Kinetics in the pH range 1.50-6.40, ESI-MS, H-1 NMR titration, and ROESY experiments were performed to characterize the complexes. High binding stoichiometry (H:G(2)) was observed for all CPA protonation states. The system is pH-dependent, and inversion of cooperativity (negative to positive) occurs by increasing the dianionic CPA(2-) concentration (allosteric behavior). Toward physiological pH, association constant K-1:1 does not change (10(4) M-1), and K-1:2 increased from 10(2) to 10(4) M-1, as well as the inhibitory effect increased up to 222-fold. NMR results elucidated the structure of the complex and allowed us to create a map of H-H interactions that describes well the diversity and number of interactions in the complex.
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