Enantioselective amino acid recognition using acyclic thiourea receptors

A series of acyclic thiourea derivatives, designed to create a cleft with f our hydrogen bond donors suitable for carboxylate recognition, have been pr epared, and their ability to bind to N-protected amino acid carboxylate sal ts has been investigated. The crystal structure of one of the thioureas has been determined showing that it forms a hydrogen bonded centrosymmetric di mer in the solid-state, in a conformation appropriate for the desired bindi ng of carboxylates. The thioureas show good discrimination between differen t amino acids and those thioureas incorporating chiral moieties show modera te enantioselectivity for a range of amino acid derivatives.