Amphoteric drugs. I. Synthesis and antiallergic activity of [4-(diphenylmethoxy)piperidino]-, [4-(diphenylmethyl)piperazinyl]- and [4-(diphenylmethylene)piperidino]alkanoic acid derivatives

Article abstract of DOI:10.1248/cpb.42.2276

A simple method of transforming classical antihistaminics into nonsedative antiallergic agents with strong effects in rat models is described. Various [4-(diphenylmethoxy)piperidinol - (series A), [4-(diphenylmethyl)piperazinyl]- (series B) and [4-(diphenylmethylene)piperidino]alkanoic acid derivatives (series C) were synthesized and examined for antiallergic activities and effects on the central nervous system (CNS), in comparison with the corresponding N-methyl derivatives (1a-c). N-Alkylcarboxylic acids (5a-c) showed stronger inhibitory effects on compound 48/80-induced lethality in rats than the corresponding N-methyl derivatives (1a-c). In particular, N-alkylcarboxylic acids (5a) in series A exhibited approximately 100-fold stronger inhibitory effects than 1a, and were the least effective in prolonging the sleeping time on hexobarbital-induced anesthesia in mice in all series. As a result of chemical modification in series A, it was found that introduction of a methyl group at the para-position on one benzene ring in the (diphenylmethoxy)piperidine system effectively reduced CNS side-effects without reducing antiallergic activity. (+)-3-[4-[(4-Methylphenyl)phenylmethoxy] piperidinol propionic acid ((+)-51), an optically active isomer of 51, exhibited a stronger antiallergic effect (ED₅₀ = 0.17 mg/kg, p.o.) than ketotifen and terfenadine in the 48 h homologous passive cutaneous anaphylaxis (PCA) test, and moreover exhibited no CNS side-effects, such as prolongation of the sleeping time on hexobarbital-induced anesthesia, at an oral dose of 30 mg/kg. Compound (+)-51 was thus proved to be a promising candidate as a nonsedative antiallergic agent.