Crystal structure of songorine chloride trihydrate, [C22H32NO3]Cl · 3H2O

Abstract

C22H38ClNO6, trigonal, R3 (no. 146), a = 28.293(2) A, c = 7.4204(7) A, V = 5144.3 A, Z = 9, Rgt(F) = 0.051, wRref(F ) = 0.137, T = 296 K. Source of material Songorine, a C20-diterpenoid alkaloid is isolated from the chloroform extract of the roots ofAconitum szechenyianumGay, wetted by 10%ammoniumhydroxide solution before. The purified compound is dissolved in a 1% hydrochloric acid solution at first. Then the solution is adjusted to pH 6.5 with a 10% NaOH solution. Colorless single crystals were obtained at room temperature for days by slowly volatilizing the solvent. Experimental details Water H atoms were located in a difference Fourier map and refined with restrained O—H bond lengths (0.85(1) A) and fixed isotropic displacement parameters (0.08A). OtherH atomswere placed at calculated positions and refined using a riding model with O—H distances restrained to 0.82 A, C—H distances restrained to 0.93 A and N—H distance restrained to 0.91 A. Discussion Songorine belongs to the class of C20-diterpenoid alkaloids, a large group of biologically active compounds of naturally occurrence. As a diterpenoid alkaloid, songorine has been found to enhance both the orthodromic population spike and field excitatory postsynaptic potential (EPSP) in CA1 region of hippocampal slices [1]. Recently, it was indicated that songorine can enhance the excitatory synaptic transmission in rat hippocampus, and was proved that songorine is a novel non-competitive antagonist at the GABAA receptor in rat brain [2]. In the title crystal structure, there are one songorine cation, one chloride ion and 3 crystal water molecules (figure top). The bond length of C12—O2 is 1.202 A, and the angles of O2−C12−C11, O2−C12−C13 and C11−C12−C13 are 121.8(4)°, 122.8(4)° and 115.4(3)°, respectively, which indicates that the C12 and O2 are sp hybridized, and C11, C12, C13 and O2 atoms are in a plane. The bond length of C17—C16 is 1.322(6)A. The angles of C13− C16−C15, C17−C16−C15 and C17−C16−C13 are 108.0(3)°, 126.2(4)° and 125.5(4)°, respectively, which show an exomethylene attached to C16. The songorine cations are interlinked by hydrogen bonds (figure bottom). Intra-molecular hydrogen bonds O6W−H6WA···Cl1 and O5W−H5WA···Cl1 link the Cl−, crystal water O5W and O6W together. The hydrogen bonds C2−H2A···O4W, O1− H1···O4W, N1−H1N···O4W fix the crystal water O4W to songorine. The intermolecular hydrogen bonds O6W− H6WB···O5W (symmetric code: x,y,z−1) and C21−H21A···O1, C19−H19B···O1, C15−H15···O2 (symmetric code: x,y,z+1), link the songorinemolecules along [001]. The hydrogen bondsO5W− Z. Kristallogr. NCS 223 (2008) 111-113 / DOI 10.1524/ncrs.2008.0047 111 © by Oldenbourg Wissenschaftsverlag, Munchen