Crystal structure of a 1,4-dihydropyridine with enantiomers showing opposite effects on calcium channels: structural features of calcium channel agonists and antagonists.

The structure of the calcium channel modulator isopropyl 4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-2,6-dimethyl-5-nitro- 3-pyridinecarboxylate has been determined by X-ray analysis. Structural and stereochemical features are discussed in relation to previously determined structures of calcium agonists and antagonists of the 1,4-dihydropyridine type, and in relation to a newly proposed model for the dihydropyridine binding site.