Crystal structure and absolute configuration of (R)-(–)-3-acetoxyquinuclidine methiodide

Abstract

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

Absolute crystal structure of (?)-N N-dimethylamphetamine methiodide

“…This configuration at the a-carbon atom is in accord with that of (-)-ephedrine (Bergin, 1971). The molecular skeleton does not differ significantly from that of amphetamine (II) which has been defined by the .. C(7) TM 3.78 9 C(9) v 3.82 .. C (9) X-ray structure of the sulfate (Bergin and Cartstr~Sm,197i).…”

“…The mean C-C bond distance in the benzene ring is 1.385 A (mean deviation 0.020 A) and the C-N bonds have a mean distance of 1.558 A. This distance is longer than the value 1.479 • given by Sutton (1965) but values ranging from 1.52 to 1.55 A have been reported more recently for bonds involving quaternary nitrogen in iodide salts (Chothia and Pauling, 1970;Kennard et al, 1970;Baker and Pauling, 1972).…”

Visible Absorption Spectra of Diaryl Carbonyl Radical Anions

“…Much less attention has been paid to the application of the Hammett-Streitwieser relation in organic electrochemistry. Recall, therefore, that it is applicable to the reaction series of arenes with the same electroactive group attached to the aryl skeletons in a given position r. Accordingly, polarographic E 1/2 values can be correlated with s (4,5). It is noteworthy that the Hammett-Streitwieser equation has been applied successfully both to reversible (3,6) and to irreversible (7) electrochemical processes.…”

Total Synthesis of Epothilone E and Analogues with Modified Side Chains through the Stille Coupling Reaction

“…The epothilones shown in Table 1 were constructed as summarized in Scheme 2. Thus, alcohol 8, prepared in 91 % yield by addition of ()-allyldiisopinocampheyl borane [()-Ipc 2 B(allyl)] to the known aldehyde 6, [21] was coupled with carboxylic acid 7 [10] (3:2 mixture with its C6,C7 diastereomer) with DCC and 4-DMAP to afford ester 9 (49 % yield, after chromatographic separation from its C6,C7 diastereomer). Exposure of 9 to catalytic amounts of [RuCl 2 (CHPh)(PCy 3 ) 2 ] in CH 2 Cl 2 at ambient temperature resulted in a mixture of (Z) and (E) cycloolefins, which were chromatographically separated on silica gel (flash column, hexanes/ethyl acetate 9/1): The required stannanes were either commercially available (5 h, i), synthesized according to literature procedures (5 b ± d, 5 j, k), [22] or prepared by the sequences shown in Scheme 3.…”