Multipoint recognition of carboxylates by neutral hosts in non-polar solvents

✍ Scribed by Blake C. Hamann; Neil R. Branda; Julius Rebek Jr.

• Book ID: 104224876
• Publisher: Elsevier Science
• Year: 1993
• Tongue: French
• Weight: 238 KB
• Volume: 34
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)91808-2

✦ Synopsis

A neutral molecular receptor of carboxylatcs has been developed using the convergent ureas as the binding site. The data indicate that chelation of the carboxylates occurs by the urea hydrogens. Asymmetric centers in the host am shown to influence the nmr spectrum of a guest bound within. Molecular recognition of anions through charge-charge interactions is well developed1 yet the binding of carboxylates with neutral hosts has seen little success. A neutral carboxylate receptor offers the advantage of uses in hydrophobic settings such as in membranes for transport. Asymmetric elements of the host, properly positioned, provide the additional possibility of enantioselection of guests. The ureas 3 and 4 were developed in this regard: they exploit the recently demonstrated ability of mono ureas to bind carboxylates,* allow for multipoint hydrogen bonding, present an asymmetric microenvironment, and offer rapid, modular synthetic combinations. Scheme