Chiral initiator-induces self-disproportionation of enantiomers via achiral chromatography: application to enantiomer separation of racemate

Resolution of enantiomers with both achiral phases in chromatography: conceptual challenge

“…3 shows a representative chromatogram. It may be considered better and a novel approach in comparison to the method reported by Tateishi et al, 22 which indeed is another approach to enantiomeric enrichment rather than resolution of racemic mixture. Nevertheless, the present approach is successful in resolving racemic mixture under achiral phases of chromatography but has the difficulty in getting quantitative yields.…”

“…Tateishi et al, 22 claimed a 'conceptually new approach for the preparation of enantiomerically pure compounds from the racemates' by achiral chromatography. In the experiment, 22 an optically pure 'chiral inducing reagent' (CIR) and the racderivative were mixed (with a mole ratio of 1 : 1), and subsequently subjected to medium pressure liquid chromatography (MPLC) on an achiral column (10 mm of silica gel) using an achiral eluent (hexane-AcOEt ¼ 1); there was no base line separation of enantiomers and, in terms of isolated yield, there was obtained only 21% or 26% of enantiomerically pure (S)-enantiomer from the starting racemic mixture when the enantiomeric composition was determined using chiral HPLC; they presumed a preferential formation of high-order heteroassociation between (R)-enantiomer of the racemic substrate and (S)-enantiomer of an optically pure CIR which transformed the initial racemate into enantiomerically enriched fractions having different retention times. [9][10][11] Though it was a report using achiral phase chromatography but the enantiomeric composition was determined using chiral HPLC.…”

The self‐disproportionation of enantiomers (SDE): The effect of scaling down, potential problems versus prospective applications, possible new occurrences, and unrealized opportunities?

“…This is a process that effectively mimics or simulates authentic SDE via chromatography but uses a coeluting chiral selector to effect the enantiodifferentiation instead of the excess enantiomer. However, it would be almost three decades before this process would actually be intentionally demonstrated by MPLC . Another important early study was by Kagan on a set of sulfoxides with compounds 4 and 5 exhibiting particularly prominent SDE applying either NP‐ or RP‐flash chromatography.…”

Self‐disproportionation of Enantiomers (SDE) of Chiral Nonracemic Amides via Achiral Chromatography

“…Chiral, additive‐induced SDE is the most novel methodology for the preparation of enantiomerically pure compounds from racemates by the addition of an enantiomerically pure inducing reagent (initiator of SDE) ,…”