The structure and absolute configuration of the title compound has been determined by single-crystal X-ray diffraction. Crystalsare triclinicwithz = 1 in a unit cell of dimensionsa = 7.61 0(4),6 = 7.41 0(4),c = 6*909(3)A, o ( = 69.75(3), p = 111.88(3), y = 112.38(3)', space group PI. The structure was solved by Patterson and Fourier methods and refined by least-squares by use of 1 637 observed three-dimensional diffractometer data to R 0.045. The absolute configuration was determined by use of the anomalous scattering effect of the iodine atom. The quinuclidine cage is twisted by ca. 12" and the ester group is planar.THE absolute configurations of (+)and (-)-3-acetoxy quinuclidine were first reported by Robinson, Belleau, and COX.^ Later Belleau and Pauling2 concluded that the original assignment was incorrect and that the dextrorotatory enantiomer possesses the (S)rather than the (R)-configuration. The absolute configuration of the laevorotatory enantiomer has now been established by X-ray diffraction techniques and we report here the results of the analysis. EXPERIMENTAL Crystals of the methiodide compound provided by Professors Belleau and Robinson are irregular plates which give a biaxial interference figure with an optic axis almost perpendicular to the plate. Triclinic, a = Crystal Data.-C1,H1,INO,, M = 31 1-16. 7*610(4), b = 7*410(4), t = 6*909(3) A, O! = 69.75(3), @ = 111*88(3), 7 = 112.38(3)', U = 326 Hia, Dm = 1*59(1) (by flotation), 2 = 1, D, = 1.59. Space group P1. Mo-Ka radiation, A = 0-7107 A; p(Mo-Ka) = 26.2 cm-l.All parameters were determined from Weissenberg and precession photographs. Refined parameters and associated standard deviations were determined using the methods described in ref.
3.I~ttwzsily Measwements.-Three-dimensional X-ray diffraction data from a small single crystal fragment (ca.0.34 x 0.14 x 0.07 mm) were collected on a computer controlled 8 four-circle diffractometer by use of Mo-K, radiation with graphite monochromator (002). A coupled 8-28 step-scan with A28 0.04", a counting time of 6 s per step and a peak-width of 1.8' were used. In the range 20 6-48' two hemispheres of data were collected, (i)All 846 unique reflections possible in each hemisphere were observed with I 2 341). A further 1102 unique reflections (+k f k f 1) in the region 28 45-60'gave 791 observed intensities. The data were corrected for Lorentz and polarisation effects but not for absorption or extinction.Structure Solution and Refinement.-A three-dimensional Patterson synthesis was carried out using the 846 data from set (i), and from this synthesis the positions of all atoms in the quinuclidine nucleus together with the N-methyl carbon atom were found. The atoms in the 1
