(1R,3S,5R,6S)-6-Acetoxy-8-methyl-3-(p-tolylsulfonyloxy)-8-azoniabicyclo[3.2.1]octane (2R,3R)-2,3-bis(benzoyloxy)-3-carboxypropanoate

The title compound, C17H24NO5S+·C18H13O8 −, is the key intermediate during the preparation of lesatropane [systematic name (1R,3S,5R,6S)-6-acetoxy-3-(4-methylphenylsulfonyloxy)tropane], a potential antiglaucoma agent. The tertiary N atom of the tropane ring is involved in intermolecular N—H⋯O hydrogen bonding, and the carboxylate groups are involved in intermolecular O—H⋯O hydrogen bonding.

X-ray structure analytical data showed that the diastereoisomeric salt is produced by the formation of hydrogen bonds.
The nitrogen atom of the tropane alkaloid is protonated to form the cation and the chiral acid is deprotonated to form anion. Each anion interacts with a cation (via N atom) forming N-H···O hydrogen bond, and chiral acid anions are linked by O-H···O hydrogen bond with each other (Fig. 2).

S3. Refinement
H atoms were located in a difference Fourier map and refined isotropically with bond restraint: N1-H1A=0.860 (18)Å, other H atoms were positioned geometrically and treated as riding, with C-H and O-H bond lengths constrained to 0.96Å for methyl, 0.97Å for methylene, 0.98Å for methine, 0.93Å for Csp 2 -H and 0.82Å for hydroxyl, with U iso (H) = 1.5U eq (methyl C and hydroxyl O) and U iso (H) = 1.2U eq (methylene and methine C). The 3094 Friedel pairs were used in the measurement of the Flack parameter (Flack, 1983).

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.  The intermolecular N-H···O and O-H···O hydrogen bonds (dashed lines).

Data collection
Bruker SMART CCD area-detector diffractometer Radiation source: fine-focus sealed tube Graphite monochromator φ and ω scans Absorption correction: multi-scan (SADABS; Sheldrick, 2002) T min = 0.863, T max = 1.000 18779 measured reflections 6550 independent reflections 5135 reflections with I > 2σ(I)  (12) 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.43913 (