Referring to Scheme A, amines of formula (X), where PG is cyclopropyl or a suitable protecting group such as a benzyl or tert-butylcarbamoyl (Boc), may be coupled with benzoic acids of formula (XI), either through activation of the acid to the acid chloride or acid fluoride followed by reaction with the amine, or directly under peptide coupling conditions, such as 1,1???-carbonyldiimidazole (CDI)