(R)-2-{2-[(S)-(2′-Benzoyloxy-1,1′-binaphthyl-2-yl)oxycarbonylamino]-3-phenylpropanamidomethyl}pyridinium picrate acetone solvate

In the crystal structure of the title compound, C43H34N3O5 +·C6H2N3O7 −·C3H6O, the large dimension and shape of the cation are responsible for the elongation of the orthorhombic unit cell. The ions and acetone molecules are linked together by a system of hydrogen bonds involving an intermolecular hydrogen bond between one N atom of the cation and the O atom of acetone and two intermolecular hydrogen bonds between the cation N atoms and the O atoms of the picrate anion. No intramolecular hydrogen bonds exist in the structure. The dihedral angle between the two naphthalene ring systems is 76.16 (13)°. The chiral C atom has a known R configuration, but this cannot be confirmed from this X-ray analysis.

In the crystal structure of the title compound, C 43 H 34 N 3 O 5 + ÁC 6 H 2 N 3 O 7 À ÁC 3 H 6 O, the large dimension and shape of the cation are responsible for the elongation of the orthorhombic unit cell. The ions and acetone molecules are linked together by a system of hydrogen bonds involving an intermolecular hydrogen bond between one N atom of the cation and the O atom of acetone and two intermolecular hydrogen bonds between the cation N atoms and the O atoms of the picrate anion. No intramolecular hydrogen bonds exist in the structure. The dihedral angle between the two naphthalene ring systems is 76.16 (13) . The chiral C atom has a known R configuration, but this cannot be confirmed from this X-ray analysis. Refinement R[F 2 > 2(F 2 )] = 0.035 wR(F 2 ) = 0.061 S = 1.11 4723 reflections 557 parameters H-atom parameters not refined Á max = 0.20 e Å À3 Á min = À0.18 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). (R)-2-{2-[(S)-(2'-Benzoyloxy-1,1'-binaphthyl-2-yl)oxycarbonylamino]-3-phenylpropanamidomethyl}pyridinium picrate acetone solvate L. Streinz, P. Hartvich, J. Ondrácek, P. Simek, K. Fejfarová and M. Dusek Comment Chiral derivatizing agents are relatively very efficient substances for derivatization of enantiomers to enable their separation by HPLC and/or spectral determination (Secco et al., 2004). Among them, the alkylchloroformates are very popular for analysis of e.g. peptides, amines or alcohols, because of their ability to react under mild conditions giving stable and largely well determined diastereomers (Hušek et al., 2006). (-)-Menthyl chloroformate or (+)-[(1-(9-fluorenyl)-ethyl]-chloroformates are good examples of such agents (Freimueller et al., 2002;Fransson et al., 1998;Christenssen et al., 1995). In order to expand the available chiral chloroformate derivatives, we have elaborated the synthesis of chloroformate containing 1-(2-hydroxynaphtha-len-1-yl)naphthalen-2-yl benzoate as a chiral auxiliary. In the bi-naphthyl auxiliary, the presence of voluminous aromatic groups and their spatial orientation massively affects the NMR chemical shifts of particular diastereomers, yielding relatively large differences of Δδ in spectra (Latypov et al., 1999;Fukushi et al., 1994a,b). Thus chiral analysis is very effective. Since the orientation of aromatic rings as well as the configuration of the molecular skeleton play an important role in the chiral analysis, the knowledge of spatial orientation of particular substituents is important for e.g. deduction of general rules useful for prediction of the absolute configuration (Růžička et al.,2000). X ray analysis may be of great benefit in this effort (Vodička et al., 2003).
In order to obtain crystals suitable for X-ray analysis, the above mentioned compound (30 mg, 0.044 mmol) was mixed with picric acid (10.2 mg, 0.044 mmol) in 0.5 ml of CHCl 3 at room temperature. After 30 min at RT the solvent was removed supplementary materials sup-2 under reduced vacuum giving 40.2 mg (100%) of product. Pure crystals were obtained by re-crystalization (20 mg) from the mixture of 0.5 ml octane and 1.0 ml acetone at room temperature.

Refinement
Hydrogen atoms were constrained to ideal positions, and isotropic temperature parameters of hydrogen atoms were calculated as 1.2U eq of the parent atom.
The 1-(2-(benzoyloxy)naphthalen-1-yl)naphthalen-2-yl fragment was refined as a rigid body with two positions in order to save parameters and to cut high angle mostly unobserved reflections without lowering the observations/parameters ratio.
The ADP parameters of the molecule were refined as common to both positions. The validity of using the common ADP parameters has been proven by comparison with TLS refinement which refines independent TLS tenzors for each molecular position. The TLS refinement converged with slightly worse R values.

Special details
Experimental. All tested samples were very weakly diffracting, especially with the used CCD detector Sapphire II. We used an exposure time 100 s / degree but most reflections above resolution 0.9 were unobserved. supplementary materials sup-4 Because of the cell parameter c above 50 Å and not very sharp diffraction spots there was danger of overlaps. In order to avoid them we used very fine scan width in omega, 0.5°, and moderate detector-to-sample distance 50 mm. The remaining overlaps were detected by the CrysAlis software using the overlap threshold parameter determined from the overlaps histogram.
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.
Because the cell parameter c was >50 Å and reflections were not very sharp there was danger of overlaps. In order to avoid this we used a very fine scan width in omega, 0.5°, and moderate detector-to-sample distance 50 mm. The remaining overlaps were detected by the CrysAlis software using the overlap threshold parameter determined from the overlaps histogram.
The program used for refinement, Jana2006, uses a 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 then the ones from the SHELX program.