Structure investigations of agonists of the natural neurotransmitter acetylcholine. VI. X-ray structure analysis of trimethyl[2-(propionyloxy)ethyl]-ammonium-iodide (O-propionylcholine-iodide).

The title compound crystallizes in the orthorhombic, noncentrosymmetric space group Pna2(1) with a = 10.241(11), b = 12.903(12), c = 9.312(9) A and with one formula unit per asymmetric unit. The stereochemically comparable torsion angles of the cation of 1 and of acetylcholine chloride are analogous. In the crystal structure the trimethylammonio methyl group is surrounded by three anions in the first coordination sphere. The geometry of a triangle formed by one of these counterions which occupies a special face of the N+C4 tetrahedron of the (CH3)3N+-CH2-R moiety, the nitrogen atom of the ammonium group and the oxygen atom of the carbonyl group is typical for nicotinic agonists.