Synthesis and configurational assignment of methyl 3-nitrooxypropyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)pyridine-3,5-dicarboxylate

Abstract

Enantiomeric (+)- and (–)-methy3-nitrooxypropyl 1,4-dihydro-2,6-dimethyl-4-(3- nitrophenyl) pyridine-3,5-dicarboxylate 1 were synthesized by esterification of the optically active monocarboxylic acids (+)-6 and (–)-6, which are available from racemate (±)-6 by optical resolution using cinchonidine and cinchonine. The absolute configuration of the key intermediates (S)-(+)-6 and (R)-(–)-6, was also unambiguously determined by the comparison with optical active (+)- and (–)-1 derived from (R)-(–)- and (S)-(+)-7 and (+)- and (–)-6, and X-ray crystallographic analysis of bromoethyl ester (R)-(–)-8 prepared from the acid (S)-(+)-7.