Molecular Pharmacology, Vol 12, 590-597, Copyright © 1976 by the American Society for Pharmacology and Experimental Therapeutics

X-ray Crystal Structure and Conformation of a Spin-Labeled Acetylcholine, DL-4-[N,N-Dimethyl-N-(ethan-2'-olacetate)amino]-2,2,6,6-tetramethylpiperidine-1-oxyliodide

¹ Paul M. Gross Chemical Laboratory, Duke University, and Department of Physiology and Pharmacology, Duke University Medical Center, Durham, North Carolina 27706

The detailed molecular geometry of the title compound, a muscarinic blocking agent, has been established by single-crystal X-ray analysis. Crystals are orthorhombic, space group Pbca, a = 18.00(1), b = 11.42(1), c = 18.42(1) A,Z = 8. The structure was solved by the heavy-atom method, and atomic parameters were refined by full-matrix, least-squares calculations to R 0.049 over 1082 statistically significant reflections from diffractometer measurements. Comparison of the results with those for known muscarinic agents revealed that whereas the O-C-C-N⁺ torsion angle at 78° is similar to those in other potent muscarinic agents, the C-O (ester)-C-C torsion angle at 99° lies outside the range predicted for muscarinic agonists.