(−)-Norfluorocurarine ethanol monosolvate

The title compound, C19H20N2O·C2H5OH, is an ethanol solvate of an indol alkaloid which was extracted from the plant Vinca erecta. The fused piperidine ring adopts an approximate boat conformation and the pyrrolidine ring an envelope conformation with one of the methylene C atoms at the flap. An intramolecular N—H⋯O hydrogen bond forms an S6 ring motif. In the crystal, norfulorocurarine and ethanol molecules are linked into a chain along the c-axis direction through N—H⋯O and O—H⋯N hydrogen bonds.

The title compound, C 19 H 20 N 2 OÁC 2 H 5 OH, is an ethanol solvate of an indol alkaloid which was extracted from the plant Vinca erecta. The fused piperidine ring adopts an approximate boat conformation and the pyrrolidine ring an envelope conformation with one of the methylene C atoms at the flap. An intramolecular N-HÁ Á ÁO hydrogen bond forms an S6 ring motif. In the crystal, norfulorocurarine and ethanol molecules are linked into a chain along the c-axis direction through N-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds.
Earlier unsolvated crystal form of (-)-norfluorocurarine was obtained from acetone and stereochemistry studied by Tashkhodjaev et al. (2011). When we used ethanol as a solvent, XRD experiments showed the solvated structure in the molar ratio 1:1. Crystals which were obtained in acetone and in ethanol showed the same absolute configuration of alkaloid molecule. But the crystal packing and intermolecular bonds are quite different.
In the molecule, the carbonyl group is oriented to N1-H group. The torsion angle of C2═C16-C17═O1 atoms is -11.7 (5)°. Therefore, the carbonyl group and N1-H group form an intramolecular hydrogen bond N1-H···O1═ C17 (Table 1). In the crystal, the hydroxyl group of solvated ethanol molecules forms intermolecular hydrogen bonds with norfluorocurarine N1 and N4 atoms ( Table 1). The hydrogen bonds links the norfluorocurarine and ethanol molecules along the c axis.

Experimental
The title compound was isolated from the chloroform fraction of the plant Vinca erecta by a known method (Yunusov et al., 1957). Norflurocurarine was dissolved in ethanol and evaporated in room temperature and obtained suitable for X-ray crystals. Since the crystal was unstable in air, we covered it with epoxide glue.

Refinement
The H atoms bonded to N1 and O2 were located in a difference Fourier map and refined isotropically. The H atoms bonded to C atoms were placed geometrically (with C-H distances of 0.98 Å for CH, 0.97 Å for CH 2 , 0.96 Å for CH 3 and 0.93 Å for C ar ) and included in the refinement in a riding motion approximation with U iso (H) = 1.2U eq (C) [U iso (H) = 1.5U eq (C) for methyl H atoms].  The molecular structure of the title compound, showing the atomic numbering scheme and displacement ellipsoids drawn at the 30% probability level.

(-)-Norfluorocurarine ethanol monosolvate
Crystal data C 19 H 20 N 2 O·C 2 H 6 O M r = 338.44 Orthorhombic, P2 1 2 1 2 1 Hall symbol: P 2ac 2ab a = 7.0138 (5) (5) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.