title: Synthesis and calcium channel antagonist activity of 1,2-dihydropyridyl analogues of nifedipine.
abstract: Calcium channel antagonist activities of 1,2-dihydropyridines (10), including that (10d) isomeric with nifedipine, were determined using the muscarinic-receptor mediated Ca2+ dependent contraction of guinea pig ileal longitudinal smooth muscle. The effect of the 4-substituent (R) on potency was cyclohexyl and phenyl greater than 2-,3- or 4-trifluoromethyl(nitro)phenyl, although the differences in activity were small. The nature of the 4-substituent (alkyl, cycloalkyl, aryl), and the position (ortho, meta, para) of further substituents (CF3 or NO2) in the case of 4-phenyl substitution, were not major determinants of activity. The weaker calcium channel antagonist activity of these compounds, relative to nifedipine, is attributed to differences in conformation between the 1,2- and 1,4-dihydropyridine ring systems and the orientation of the 4-aryl substituent. In the synthetic work, the required 1,2-dihydropyridines (10), were synthesized by a route involving regiospecific ortho-directed reduction of the 1-oxide analogues (9) using borane. NMR spectrometric studies indicated that the 4-(2-trifluoromethyl) analogue (10a) exists as a single rotamer (10a'), whereas the 4-(2-nitrophenyl) analogue (10d) exists as a 10:3 mixture of rotamers (10d') and (10d") at 25 degrees C in CDCl3 solution.
authors.affiliation: Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Wynn
authors.forename: M
authors.initials: M
authors.lastname: Ramesh
authors.forename: W C
authors.initials: WC
authors.lastname: Matowe
authors.forename: M W
authors.initials: MW
authors.lastname: Wolowyk
authors.forename: E E
authors.initials: EE
authors.lastname: Knaus
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000138:chemical synthesis*; D015220:Calcium Channels / Q000187:drug effects; D055598:Chemical Phenomena; D002621:Chemistry; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009543:Nifedipine / Q000031:analogs & derivatives*; D013329:Structure-Activity Relationship
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D009543:Nifedipine