Structure and molecular chirality of the acetonitrile adduct of the 2:1 salt of quinidine with biphenyl 5,5′-dinitro-2,2′-dicarboxylic acid (5,5′-dinitrodiphenic acid)

Abstract

The molecule of the 2∶1 salt consists of two quinidine cations and the 5,5′-dinitrodiphenic anion. Both of the quinidine cations are protonated at the nitrogen atoms of the quinuclidine fragments. Owing to the interlocking hydrogen bonds between quinidine and the dinitrodiphenic ions, a rigid structure of the salt molecule has been formed. The alkaloid molecular conformation around the C(8)-C(9) bond is “open.” The conformational parameters of 5,5′-dinitrodiphenic anion are considerably changed in comparison with the conformation of diphenic acid in the solid state. The absolute configuration of biphenyl 5,5′-dinitro-2,2′-dicarboxylic anion (R) is defined by the negative torsion angles around the line which connects the centers of both phenyl rings, and is the reverse of that observed in the diphenic acid-quinine salt. The present data confirm the observation that the chirality of the salt is controlled by the chirality of theCinchona alkaloid molecule.