The hydrochloride salt of 4-hydroxy-N,N-di-n-propyltryptamine (4-HO-DPT)

The first single-crystal structure of the hydrochloride salt of a psilocin analogue, specifically 4-hydroxy-N,N-di-n-propyltryptamine (4-HO-DPT) is reported.

The 4-HO-DPT cation and the chloride anion are held together in the asymmetric unit via O-HÁ Á ÁCl hydrogen bonds. The cation possesses a near planar indole group, with a mean deviation from planarity of 0.011 Å . The ethylamino group is turned away from the plane with a C1-C2-C9-C10 torsion angle of 101.54 (18) . The N-H of the indole ring, and the N-H of the ammonium group also both hydrogen bond to other symmetry-generated chloride anions through N-HÁ Á ÁCl interactions (Table 1). The N-HÁ Á ÁCl indole-tochloride hydrogen bond and the O-HÁ Á ÁCl hydrogen bond combine to link the ions together in chains with graph-set notation C 1 2 (8). The N-HÁ Á ÁCl indole-to-chloride hydrogen bonds and the N-HÁ Á ÁCl ammonium-to-chloride hydrogen bonds combine to generate rings with graph-set notation R 2 4 (18) (Etter, et al. 1990). The N-HÁ Á ÁCl ammonium-tochloride hydrogen bonds and O-HÁ Á ÁCl hydrogen bonds combine to generate rings with graph-set notation R 2 4 (20). The two rings and chains combine to give ladder chains along [010], Fig. 2.

Synthesis and crystallization
Freebase 4-hydroxy-N,N-di-n-propyltryptamine (50 mg, 0.19 mmol) was dissolved in dichloromethane, and 160 mL of hydorochloric acid (1.25 M in ethanol, 0.20 mmol) were added with stirring at room temperature. The mixture was stirred for 30 minutes, resulting in a white precipitate which was isolated via vacuum filtration and washed with diethyl ether to yield 28 mg of the salt. A second crop was collected by concentrating and cooling the filtrate to give another 13 mg of the salt Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x; y À 1; z; (ii) Àx þ 2; Ày þ 1; Àz þ 1.

Figure 2
The crystal packing of 4-hydroxy-N,N-di-n-propyltryptammonium (4-HO-DPT) chloride, viewed along the c axis. The hydrogen bonds (Table 1) are shown as dashed lines. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen atoms not involved in hydrogen bonds are omitted for clarity.

Figure 1
The molecular structure of 4-hydroxy-N,N-di-n-propyltryptammonium (4-HO-DPT) chloride, showing the atom labeling. Displacement ellipsoids are drawn at the 50% probability level. A hydrogen bond is shown as a dashed line.
(73% yield). Crystals suitable for X-ray diffraction studies were grown by the slow evaporation of a methylene chloride/ methanol mixture. The sample was analyzed by nuclear magnetic resonance.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.  Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.