Roy W. Baker

Conformation of acetylcholine at muscarinic nerve receptors: Crystal and molecular structure of 2-trimethylammoniummethyl-5-methyl furan iodide (5-methylfurmethide iodide)

Abstract 2-Trimethylammoniummethyl-5-methyl furan (5-methylfurmethide) is a potent cholinergic agonist at muscarinic nerve receptors. The conformation of the molecule, as shown by crystal structure analysis, is restricted by steric hindrance. The only similar conformation of acetylcholine has τ(N+CCO) synclinal and τ(CCOC) antiplanar. This is the conformation found in solution and in crystals of the chloride, and it is believed to be the one relevant to interaction with muscarinic nerve receptors.

Molecular Structure of LSD

The molecular configuration of lysergic acid diethylamide (LSD) in crystals of the iodobenzoate has been determined by using x-ray diffraction techniques. The configuration shows strain and steric hindrance and the conformation is fixed. Some of the implications of this for the hallucinogenic activity of LSD are discussed.

Preparation and properties of some mercury halide–platinum compounds and crystal structure of di-µ-chloro-(dichloromercurio)bis(dimethylphenylphosphine)platinum(II)

The compounds (I)—(VI)(PPhMe2)2PtX2(HgY2)(X = Cl, Br, or I; Y = Cl or Br) have been prepared by the action of mercury(II) halide on cis-(PPhMe2)2PtX2. The crystal structure of (I; X = Y = Cl) has been determined from diffractometer data. Crystals are monoclinic, space group P21/c, with Z= 4 in a unit cell of dimensions : a= 909·2(3), b= 1043·8(4), c= 2428·6(8) pm, β= 105·12(2)°. The structure was solved by Patterson and Fourier methods and refined by least-squares to R 0·057 for 2184 independent reflections. The complex contains two bridging chlorine atoms between Pt and Hg, the co-ordination being essentially square planar about Pt and distorted tetrahedral about Hg. Bond lengths suggest that HgCl2 is only weakly co-ordinated.

Crystal structure and absolute configuration of (R)-(–)-3-acetoxyquinuclidine methiodide

The structure and absolute configuration of the title compound has been determined by single-crystal X-ray diffraction. Crystals are triclinic with Z= 1 in a unit cell of dimensions a= 7·610(4), b= 7·410(4), c= 6·909(3)A, α= 69·75(3), β= 111·88(3), γ= 112·38(3)°, space group P1. The structure was solved by Patterson and Fourier methods and refined by least-squares by use of 1637 observed three-dimensional diffractometer data to R 0·045. The absolute configuration was determined by use of the anomalous scattering effect of the iodine atom. The quinuclidine cage is twisted by ca. 12° and the ester group is planar.

The preparation and crystal structure of tristriphenylphosphinetriphenylarsinerhodium(I) hydride, (Ph3P)3(Ph3As)HRhI,½C6H6

Crystals of tristriphenylphosphinetriphenylarsinerhodium(I) hydride are isomorphous with those of tetrakistriphenylphosphinerhodium(I) hydride with the arsenic and phosphorus atoms randomly occupying the four tetrahedral heavy-atom-ligand positions and the hydrogen atom trans to both arsenic and phosphorus.

Crystal and molecular structure of a tetranuclear cobalt(II)–tropolonate complex: [Co4(C7H5O2)8(H2O)2]

Crystals of the title compound are monoclinic, a= 13.341 (5), b= 18.634(9), c= 11.603(5)A, β= 171.43(3)°, Z= 2, space group P21/c. The structure was determined from X-ray diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares calculations to R 0.067 for 2 070 observed reflections. There are two distinct cobalt atoms in the structure, both achieving a co-ordination number of six but with considerably distorted octahedral geometry. Of the four independent tropolone ligands in the asymmetric unit, three chelate and have one bridging oxygen atom while the other ligand chelates and does not bridge. A water molecule completes the co-ordination polyhedra. The Co–O distances vary from 2.051 (6) to 2.1 49(9)A, with mean distances corresponding to whether the ligand chelates (2.060 A), chelates and bridges (2.084 A), or forms a bridging bond (2.137 A). The molecules are hydrogen-bonded via the water molecules and tropolone oxygen atoms. The stability of the structure is due to efficient lattice packing and hydrogen bonding, both facilitated by the compact planar structure of the ligand.

Crystal structure of (pentafluorophenyl)(triphenylphosphine)gold(I)

The crystal structure of the title compound has been determined by single-crystal X-ray diffraction. Crystals are monoclinic, space group P21/c with Z= 4 in a unit cell of dimensions: a= 834·0(3), b= 1199·1(4), c= 2214·6(7) pm, β= 98·33°. Refinement of 1834 three-dimensional diffractometer data led to R 0·055. The gold atom is linearly co-ordinated, with C–Au–P 178°, Au–P 227(1) and Au–C 207(2) pm. The phenyl and pentafluorophenyl rings are planar and their bond distances and angles have the expected values. The structure is compared with other bisco-ordinated gold compounds containing Au–C or Au–P bonds.

Crystal and molecular structure of hexakisantipyrineyttrium tri-iodide

The structure of the title compound has been determined by single-crystal X-ray diffraction. Crystals are rhombohedral with Z= 3 in a unit cell (based on hexagonal axes) of dimensions: a= 13·896(3), c= 31·986(6)A, γ= 120°, space group R. The structure was solved by Patterson and Fourier methods and refined by least-squares using 825 observed three-dimensional photographic data to R 0·073. The Y3+ ion is co-ordinated to six antipyrine molecules through the carbonyl oxygen and the molecular symmetry is , S6. The angle between the normals to the phenyl ring and the pyrazole ring is 58°.

Crystal and molecular structure of hexapyrronium bromide [3-(2-cyclohexyl-2-hydroxy-2-phenylacetoxy)-1,1-dimethylpyrrolidinium bromide]

The structure of the title compound (I) has been determined by single-crystal X-ray diffraction. Crystals are monoclinic with Z= 4 in a unit cell of dimensions: a= 17·167(8), b= 9·796(4), c= 12·185(6)A, β= 101·63(2)°, space group P21/c. The structure was solved by Patterson and Fourier methods and refined by least-squares to R 0·048 for 1593 observed diffractometer data. All hydrogen atoms were located. The ester bridge is planar: the phenyl group makes an angle of 63° and the mean plane of the cyclohexyl group an angle of 69° with the ester plane. The angle between the phenyl group and mean plane of the cyclohexyl group is 84°. The pyrrolidine ring is in the envelope conformation with the nitrogen atom out of the plane. A hydrogen bond between the bromide ion and the hydroxy oxygen was found.

Crystal structure of trimethyl-[4-(2-oxopyrrolidin-1-yl)but-2-ynyl]ammonium iodide

The structure of the title compound has been determined by single-crystal X-ray diffraction. Crystals are triclinic with Z= 2 in a unit cell of dimensions a= 9·382(4), b= 7·502(3), c= 11·166(4)A, α= 111·13(5), β= 69·89(5), γ= 93·23(5)°, space group P. The structure was solved by Patterson and Fourier methods and refined by least-squares to R 0·051 for 2501 observed three-dimensional diffractometer data. The amide group N(1), C(5), O(1), C(6) is planar and the orientation of the trimethylammonium group is symmetrical with respect to C(3)–C(4) such that τ[C(3)–C(4)–N(2)–C(10)] is almost 180°.