NMR spectral enantioresolution of spirobrassinin and 1-methoxyspirobrassinin enantiomers using (S)-(−)-ethyl lactate and modeling of spirobrassinin self-association for rationalization of its self-induced diastereomeric anisochromism (SIDA) and enantiomer self-disproportionation on achiral-phase chromatography (ESDAC) phenomena

A comprehensive examination of the self-disproportionation of enantiomers (SDE) of chiral amides via achiral, laboratory-routine, gravity-driven column chromatography

“…Here the magnitude of the SDE was markedly reduced in comparison to the results obtained with silica gel, though still notable nonetheless. But the result, given that the magnitude of the SDE was effectively impervious to all other parameter changes, lends credence to the premise of Klika et al 19 whereby it was asserted that the SDE phenomenon is not just a question of a preference between homo-and heterochiral dimers, but the relative stability of these homo-and heterochiral dimers as the environment changes, e.g. from solution in the eluent in the interstitial spaces to the pores of the stationary phase.…”

“…Thus oligomer formation, in addition to dimer formation, or alternative binding modes must be occurring whenever aberrant behavior is observed. The latter explanation has been proposed, 19,22 with some legitimacy, to account for the dramatic behavior of the spirobrassinins. 21 Thus it is clear that the graphical representations are not ideal with respect to mathematical modeling assuming a single intermolecular interaction and the formation of only one type of transitory aggregate structure 11,12 and/or the differential formation of the dimers under the various environments of the chromatography.…”

Optical Purifications via Self‐Disproportionation of Enantiomers by Achiral Chromatography: Case Study of a Series of α‐CF3‐containing Secondary Alcohols

“…5,8,[26][27][28][29][30][31][32][33][34][35] Similar to the phenomenon of nonlinear effects in asymmetric catalysis, 27,28 the origin of the SDE under the conditions of achiral chromatography is the dynamic formation of homo-or heterochiral high-order species which have different chromatographic behaviour as compared with monomers or other low-order species. 5,8,[26][27][28][29][30][31][32][33][34][35] Similar to the phenomenon of nonlinear effects in asymmetric catalysis, 27,28 the origin of the SDE under the conditions of achiral chromatography is the dynamic formation of homo-or heterochiral high-order species which have different chromatographic behaviour as compared with monomers or other low-order species.…”

“…The SDE via achiral chromatography is of very general nature and, under certain conditions, can be expected for virtually any chiral compound. 5,8,[26][27][28][29][30][31][32][33][34][35] Similar to the phenomenon of nonlinear effects in asymmetric catalysis, 27,28 the origin of the SDE under the conditions of achiral chromatography is the dynamic formation of homo-or heterochiral high-order species which have different chromatographic behaviour as compared with monomers or other low-order species. [3][4][5][6] Therefore, different compounds possessing different qualities of the corresponding homo-and heterochiral interactions show different magnitude of the SDE; or readiness for separation of racemate from the excess enantiomer.…”

Influence of the basis set on the calculation of the absolute 13C shieldings of methyl derivatives (CH3X with X = CH3, CN, NH2, NO2, OH, F) with special emphasis in the cases of X = Cl, Br, SH, SeH, and PH2

“…The first one is very numerous, but some examples of 2010 can be found in [5][6][7][8][9][10]. The second one belongs to a known family of computational chemists: Gauss [11], Bühl et al [12], Haase and Sauer [13], Enevoldsen and Oddershede [14], Ruud et al [15], Kupka [16], Rablen et al [17], Schleyer et al [18], Okazaki and Laali [19], Contreras et al [20], Kaupp and coworkers [21][22][23] as well many others.…”