. . "Additional suitable modulating groups may include other cyclic and heterocyclic compounds and other compounds having similar steric ???bulk.??? Non-limiting examples of compounds that can be used to modify a ??-AP include N-acetylneuraminic acid, cholic acid, trans-4-cotininecarboxylic acid, 2-imino-1-imidazolidineacetic acid, (S)(???)-indoline-2-carboxylic acid, (???)menthoxyacetic acid, 2-norbor" . .