Absolute structure of the chiral pyrrolidine derivative (2S)-methyl (Z)-5-(2-tert-butoxy-1-cyano-2-oxoethylidene)pyrrolidine-2-carboxylate, a compound with low resonant scattering

Abstract

The light-atom com­pound (2S)-methyl (Z)-5-(2-tert-but­oxy-1-cyano-2-oxo­ethyl­idene)pyrrolidine-2-carboxyl­ate is an enanti­opure coordination partner for cations. Despite its only minor resonant scattering, the absolute structure was determined by a combination of diffraction, CD spectroscopy and theoretical calculations.

Crystal structure, Hirshfeld surface analysis and energy framework study of 6-formyl-7,8,9,11-tetrahydro-5H-pyrido[2,1-b]quinazolin-11-one

“…In the absence of heavy atoms, resonant scattering in (1) is minor, with Friedif (Flack & Shmueli, 2007) of 28. We have recently investigated a case of similar low resonant scattering in a Sohnke group, where the absolute structure could be linked to the absolute configuration of the target molecule, and chemical and spectroscopic information could help (Wang & Englert, 2019). As might be expected, the commonly used indicators for diffraction-based assignment of the absolute structure of (1) were associated with rather large standard uncertainties: the Flack parameter (Flack, 1983) The asymmetric unit of (1) with the atom-numbering scheme.…”