Synthesis and Crystal Structure of a Novel n-Substituted 1,4-dihydropyridine

nifedipine. 1,4-Dihydropyridine (1,4-DHP) moiety is very interestingbecause of its recognition as a calcium channel antagonist, chemother-apeutic agent for multidrug resistance (MDR) reversal [2] in tumorcells, potent immunomodulator [3], and antitubercular agent [4]. Afurther study of N-alkylated DHP at the labile hydrogen of the DHPskeleton proved that it is important for MDR reversal in tumor cells,and this has created new interest in N-phenyl substituted 1,4-dihydro-pyridines [5]. In structure–activity relationships, the effects of substi-tution on the 1,4-dihydropyridine rings have been meticulouslystudied [6]. These have indicated specific conformational details thatcorrelate with high binding efficiency [7].The crystallographic studies of both 1,4-dihydropyridine antagonistand agonist show several common conformational features . The DHPantagonist blocks transmembrane Ca