Crystal Stucture of [7(S)-(1α,2β,4β,5α,7β]-7-(3-Hydroxy-1-oxo-2-phenyl-propoxy)-9,9-dimethyl-3-oxa-9-azoniatricyclo[3.3.1.0^2,4]nonane Bromide Monohydrate (Methscopolamine Bromide Monohydrate)

through two different classes of receptors which are known to be muscarinic and nicotinic cholinergic receptors. Both receptors are named for their ability to bind muscarine and nicotine compounds, respectively. Nicotic receptors belong to the superfamily of neurotransmitter-gated ion channels, whereas muscarinic receptors belong to the superfamily of the G protein (GTP binding regulatory proteins)-coupled receptors; there are five subtypes of this receptor.1,2 Using both high-affinity antagonist quinuclidinylbenzilate and Nmethylscopolamine have helped to establish the pharmacological diversity of the muscarinic receptors.2 Mutagenesis studies of the m2 and m3 muscarinic receptors using [3H]-N-methylscopolamine as a ligand have provided additional information about the nature of the ligand binding site in these receptors.3,4 Biochemical, pharmacological and genetic approaches combined with structural information obtained from Xray crystallography will help to reveal the key elements in the signaling mechanism and molecular details of ligand–receptor interactions in the muscarinic receptors. In this paper we describe the X-ray structure determination of [7(S)-(1α,2β,4β,5α,7β]-7-(3-hydroxy-1-oxo-2phenylpropoxy)-9,9-dimethyl-3-oxa-9-azoniatricyclo[3.3.1.0 2,4]nonane bromide monohydrate. The X-ray data were collected using graphite-monochromatized MoKα radiation. No absorption correction was applied. Table 1 summarizes the crystal and experimental data. The molecular structure of the title compound is shown in Fig. 2. The molecule consists of a nucleus that comprises a system involving a threemembered ring (A), a five-membered ring (B) and a six-membered ring (C). The A and B rings are fused at C(2)–C(4) and the C ring is fused at C(1)–N(9)–C(5) to the B ring. For the puckering-parameter values (φ2, θ2 and Q), the six-membered rings (C) occur in a chair conformation, while ring B (φ2 and Q) occurs in an envelope conformation.5 The absolute configuration of the title compound was assigned using anomalous dispersion for the Br, O and C atoms. Similar bond 203 ANALYTICAL SCIENCES FEBRUARY 1999, VOL. 15