Synthetic receptors for chiral recognition of carboxylates

This thesis is principally concerned with the synthesis of a range of receptors and their binding properties with amino acid derivatives. Chapter 1 provides an introduction to supramolecular chemistry and reviews, in the main part, literature contributions to enantioselective recognition. Chapter 2 describes two combinatorial approaches to enantioselective recognition. Chapter 3 discusses the properties of a bisthiourea receptor, which had been found to be highly enantioselective towards N-Boc protected glutamate dianion. Substitution of the bulky N-boc protecting group with the smaller N-Ac group reduced the enantioselective recognition properties of the macrocycle, indicating that the guest’s side chain actively participate to discriminate the two enantiomers. Molecular modelling simulation experiments were used to understand the anomalous solvent-dependent behaviour, due to the formation of alternative conformers in DMSO and chloroform. Chapter 4 describes a thiourea based receptor, monomer analogue to the bisthiourea discussed in chapter 3. This macrocycle showed only modest enantioselectivity toward some amino acid derivatives. Crystal structures of the host in CH3CN and DMSO were obtained, and used as starting point for computational studies. Chapter 5 describes a new family of thiourea based receptors. Unfortunately, these receptors are soluble only in polar solvents, such as DMSO, in which showed only weak or inexistent enantioselectivity.