Orthorhombic polymorph of (6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-1-yl)methanol

The asymmetric unit of the title compound, C12H17NO3, contains two molecules with different conformations. It is a polymorph of the monoclinic form [El Antri et al. (2004 ▶). Molecules, 9, 650–657]; the samples were crystallized at different temperatures from the same solvent. In both structures, molecules are linked by O—H⋯N hydrogen bonds, forming chains. The conformations of the chains and their packing differ markedly in the two polymorphs.

The asymmetric unit of the title compound, C 12 H 17 NO 3 , contains two molecules with different conformations. It is a polymorph of the monoclinic form [El Antri et al. (2004). Molecules,9,[650][651][652][653][654][655][656][657]; the samples were crystallized at different temperatures from the same solvent. In both structures, molecules are linked by O-HÁ Á ÁN hydrogen bonds, forming chains. The conformations of the chains and their packing differ markedly in the two polymorphs.
In a previous study (El Antri et al., 2004), a single-crystal of 1-hydroxymethyl-7-8-dimethoxy-1,2,3,4-tetrahydroisoquinoline was measured at 173 K. A monoclinic symmetry (S. G.: P2 1 ) has been found in the structure. Re-measurement, at 150 K, of another crystal from the same plant extract but crystallised at a different temperature, revealed the same composition C 12 H 17 NO 3 ( Fig. 1) but with an orthorhombic symmetry (S. G.: P2 1 2 1 2 1 ). Testing measurements between 120 K and room temperature revealed however no phase transition. Moreover, no simple transformation between the monoclinic and orthorhombic unit cells could be found. Thus, 1-hydroxymethyl-7-8-dimethoxy-1,2,3,4-tetrahydroisoquinoline exists in two crystallographic forms. We report in the present study on the crystal determination of the new orthorhombic 1-hydroxymethyl-7-8-dimethoxy-1,2,3,4-tetrahydroisoquinoline. As in the monoclinic form, the molecules C 12 H 17 NO 3 are connected by strong hydrogen bond O-H···N (Fig. 2). In the monoclinic previously published structure the chain runs along a and the molecules have alternating orientation with respect to the projection of hydrogen bonds into the a axis (Fig. 3a).
On the other hand, in the orthorhombic structure reported here the chain direction is along b and the molecules are oriented in one side with respect to the projection of hydrogen bonds into the b axis ( Fig. 3  The asymmetric unit of the title compound contains two independent molecules, which differ in conformation of the tetrahydroisoquinoline ring (Fig. 4). The nitrogen atoms in each of the molecules are oriented on opposite sides of the ring.

The conformation of the molecules may be influenced by intermolecular O-H···N hydrogen bonding involving both N1
and N2 atoms.
Distances and angles are of the same magnitude in the two crystals. The heterocyclic ring of tetrahydroisoquinoline adopts a half chair conformation. The conformation of the asymmetric carbon atoms are the same in both asymmetric molecules.

Experimental
Alkaloids under investigations were extracted from the seeds of Calycotome villosa (Poiret) Link Subsp as in (El Antri et al., 2004). The same procedure was used for extractions and crystals synthesis. However, the experiments took place at different room temperatures.
supplementary materials sup-2 Refinement Positions of hydrogen atoms bounded to nitrogen and oxygen were refined using a distance restraint. The other H atoms were fixed in the ideal geometry. The methyl H atoms were allowed to rotate freely about the adjacent C-O bonds. The isotropic atomic displacement parameters of hydrogen atoms were evaluated as 1.2×U eq of the parent atom. Fig. 1. :. Ellipsoid plot of the title compound. Anisotropic displacement parameters drawn at the 50% probability level.   sup-3 (6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-1-yl)methanol

Special details
Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F 2 for refinement carried out on F and F 2 , respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement.
The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program.