Tetrakis(phenylamidinium)-Substituted Resorcin[4]arene Receptors for the Complexation of Dicarboxylates and Phosphates in Protic Solvents

Three bowl‐type cavitand receptors (1 – 3), consisting of a resorcin[4]arene core with four convergent phenylamidinium groups, were prepared in gram quantities by efficient synthetic routes (Schemes 1 and 2) for the recognition of organic anions in CD3OD and D2O. The key steps in the syntheses are t...

Full description

Saved in:
Bibliographic Details
Published in:Helvetica chimica acta 2000-01, Vol.83 (1), p.93-113
Main Authors: Sebo, Lubomir, Diederich, François, Gramlich, Volker
Format: Article
Language:English
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Three bowl‐type cavitand receptors (1 – 3), consisting of a resorcin[4]arene core with four convergent phenylamidinium groups, were prepared in gram quantities by efficient synthetic routes (Schemes 1 and 2) for the recognition of organic anions in CD3OD and D2O. The key steps in the syntheses are the Suzuki cross‐coupling reactions between the tetraiodo cavitands 12, 13, and 23, respectively, with the m‐cyanophenylboronic ester 14 and subsequent conversion of the nitrile to amidinium groups by the Garigipati reaction. Compounds 1 and 2 displayed limited solubility in protic solvents, and evidence for stoichiometric host‐guest association between 2 and AMP (28) could only be obtained by FAB‐MS analysis of a complex precipitated from MeOH (Fig. 2). In contrast, receptor 3 with four triethyleneglycol monomethyl ether side chains was readily soluble in the protic environments, and complexation of isophthalates and nucleotides 25 – 37 was extensively studied by 1H‐NMR titrations and Job's method of continuous variation. In CD3OD and pure D2O, isophthalates 25 and 26 formed stable 1 : 2 host‐guest complexes (Table 1 and Fig. 3), whereas upon addition of borate (pH 9.2) or Tris/HCl buffer (pH 8.3) to the D2O solution, the tendency for higher‐order complexation vanishes. Stable 1 : 1 complexes formed in the buffered solutions (Fig. 4) with 5‐methoxyisophthalate being selectively bound over the 5‐NO2 derivative. Complexation‐induced upfield shifts of specific isophthalate 1H‐NMR resonances (Fig. 5) suggest a preferred inclusion of the methoxyphenyl ring into the receptor cavity. Cavitand 3 forms stable 1 : 1 host‐guest complexes with nucleotides in Tris/HCl‐buffered D2O. Association constants increase strongly with increasing guest charge in the series cAMP
ISSN:0018-019X
1522-2675
DOI:10.1002/(SICI)1522-2675(20000119)83:1<93::AID-HLCA93>3.0.CO;2-5