Cleft receptors with donor-spacer-donor-acceptor hydrogen bonding arrays: Implications for amino acid recognition

ORGN 701

William E. Allen, allenwi@ecu.edu1, Andrew L. Sargent1, and Daniel K. Barnhill2. (1) Department of Chemistry, East Carolina University, science and Technology Building, Greenville, NC 27858, (2) Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712
In the design of artificial receptors for carboxylic acids, a hydrogen-bonding array of Donor-Spacer-Donor-Acceptor groups offers several advantages. Binding occurs according to mode A, which places the most acidic proton of the guest close to the H-bond Acceptor, while the lone pair electrons of the carbonyl O are “saturated” with bonds from the D-H units. The identity of the spacer group S appears to matter little in this mode, as long as it is small enough to limit steric congestion in the binding pocket. As part of a program to evaluate the supramolecular chemistry of biheterocycles, we have examined the factors that drive recognition between the –COOH unit of amino acids and D-S-D-A receptors. Comparing a new set of 2,2'-biimidazoles to other cleft-shaped hosts, we find that the accessibility and basicity of the groups S are critically important to the recognition process. The results call into question the assumption that mode A is always operative, and have consequences for the design of enantioselective receptors.

 

Asymmetric Reactions, Molecular Recognition, Self Assembly, Bioorganic Chemistry, Process R&D
8:00 PM-10:00 PM, Wednesday, 16 March 2005 Convention Center -- Hall D, Poster

Division of Organic Chemistry

The 229th ACS National Meeting, in San Diego, CA, March 13-17, 2005