TY - JOUR T1 - X-ray Crystal Structure and Conformation of a Spin-Labeled Acetylcholine, DL-4-[<em>N,N</em>-Dimethyl-<em>N</em>-(ethan-2'-olacetate)amino]-2,2,6,6-tetramethylpiperidine-1-oxyliodide JF - Molecular Pharmacology JO - Mol Pharmacol SP - 590 LP - 597 VL - 12 IS - 4 AU - ANDREW T. MCPHAIL AU - MOHAMED B. ABOU-DONIA AU - GERALD M. ROSEN Y1 - 1976/07/01 UR - http://molpharm.aspetjournals.org/content/12/4/590.abstract N2 - 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. ER -