64520-58-7Relevant articles and documents
Diastereoface Selectivity During Phthalimidonitrene Additions to (E)- and (Z)-Configurated α,β-Unsaturated Esters, Induced by a Chiral Center in the γ-Position
Chilmonczyk, Zdzislaw,Egli, Markus,Behringer, Christoph,Dreiding, Andre S.
, p. 1095 - 1106 (1989)
In-situ-generated phthalimidonitrene was added to five α,β-unsaturated esters containing a chiral secondary O-function at C(γ).The additions were fully suprafacial, inasmuch as the (E)-isomers 1 afforded only the trans-aziridines 2 and 3 (J(β,γ)=4.8-5.1 Hz) and the (Z)-isomers 4 only the cis-aziridines 5 and 6 (8.2-8.5 Hz).The products 2, 3, 5, and 6 where shown to possess the arabino-, xylo-, ribo-, and lyxo-configuration, respectively, by X-ray structure analysis of 2b, 2d, and 6a.The diastereoface selectivity of the nitrene addition, induced by the chiral substructure around C(γ), resulted in more 2 than 3 from 1, but more 6 than 5 from 4, which means that the preference of attack at the double bond switches from one side to the other depending on the C=C configuration.The preferences were higher at lower temperature.The aziridines 2a, 2d, and 3d exhibit 1H-NMR-visible isomerism at the ring N-atom; the major (78-95percent) invertomer A is always the one with the phthalimido group in trans-position to the (larger) substructure around C(γ).The other aziridines only show 1H-NMR signals of one invertomer, which - by steric reasoning - ought to be A; this is confirmed by a 1H-NMR argument for 3a, 5a, 6a, 5c, and 6c.
Stereocontrolled Synthesis of Tetrafluoropentanols: Multivicinal Fluorinated Alkane Units for Drug Discovery
Bentler, Patrick,Erdeljac, Nathalie,Bussmann, Kathrin,Ahlqvist, Marie,Knerr, Laurent,Bergander, Klaus,Daniliuc, Constantin G.,Gilmour, Ryan
supporting information, p. 7741 - 7745 (2019/09/03)
A stereodivergent synthesis of four diastereomeric 2,3,4,5-tetrafluoropentanols is disclosed. X-ray crystallographic analysis reveals conformations that manifest sequential stereoelectronic gauche effects (σC-H/C → σC-F*), thereby generating topological diversity via subtle C(sp3)-H to C(sp3)-F exchange. Two representative tetrafluoro arrays have been incorporated into truncated analogues of Gilenya for the management of relapsing remitting multiple sclerosis. These closely similar multivicinal fluoroalkanes have notably different physicochemical profiles and were found to be stable in the presence of human microsomes.
Assignment of the relative and absolute stereochemistry of two novel epoxides using NMR and DFT-GIAO calculations
Moraes,Alvarenga,Demuner,Viana
, p. 109 - 115 (2018/05/03)
Considering the potential biological application of isobenzofuranones, especially as agrochemical defensives, two novel epoxides, (1aR,2R,2aR,5S,5aS,6S,6aS)-5-(hydroxymethyl)hexahydro-2,6-methanooxireno[2,3-f]isobenzofuran-3(1aH)-one (9), and (1aS,2S,2aR,5S,5aS,6R,6aR)-5-(hydroxymethyl)hexahydro-2,6-methanooxireno[2,3-f]isobenzofuran-3(1aH)-one (10), were synthesized from the readily available D-mannitol in six steps. The multiplicities of the hydrogens located at the bridge of the bicycle are distinct for epoxides 9 and 10 due to W coupling, and this feature was employed to confirm the assignment of these nuclei. Besides analyses of the 2D NMR spectra, the assignments of the nuclei at the epoxide ring were also inferred from information obtained by theoretical calculations. The calculated 1H and 13C NMR chemical shifts for eight candidate structures were compared with the experimental chemical shifts of 9 and 10 by measuring the mean absolute errors (MAE) and by the DP4 statistical analysis. The structures and relative configurations of 9, and 10 were determined via NMR spectroscopy assisted with theoretical calculations. As consequence of the enantioselective syntheses starting from a natural polyol, the absolute configurations of the epoxides 9 and 10 were also defined.
