The Separation of Hypericin's Enantiomers and Their Photophysics in Chiral Environments¶

Abstract

We report the first separation of the enantiomers of hypericin. Their steady-state optical spectra and ultrafast primary photoprocesses are investigated in chiral environments. Within experimental error, there is no difference between the two enantiomers in any of the systems considered. This is consistent with the emerging picture that the rich and extended absorption spectrum of hypericin is not a result of ground-state heterogeneity. It is also consistent with the observation that the spectra and photophysics of hypericin are generally insensitive to environments in which it does not aggregate.

Determination of enantiomerization barriers of hypericin and pseudohypericin by dynamic high‐performance liquid chromatography on immobilized polysaccharide‐type chiral stationary phases and off‐column racemization experiments

“…18,24,25,29,36 Experimental enantiomerization barriers in the range of 97.1-99.6 kJ/ mol for 1 and of 98.9-101.4 kJ/mol for 2 agree reasonably well with those found earlier by computational and 1 H Experimental conditions are detailed in the text. n.d., not determined.…”

“…36) and a lack of enantioselectivity in steady-state spectra of 1 in different chiral environments including proteins 29 no data are available whether enantiodiscrimination is relevant for the biological fate and effect profile of this pharmacologically important class of compounds. Stereochemical aspects of the biogenesis of 1 (and 2) are unknown as well.…”

On the Diffusion of Hypericin in Dimethylsulfoxide/Water Mixtures—The Effect of Aggregation

“…The propeller conformation of Hyp (and Hyp − ) is a racemate with two possible enantiomeric forms, denoted as ( P ) and ( M ) . The enantiomers of Hyp were investigated theoretically and experimentally by other authors. ,− In the present work, the structure of the homochiral ( P )( P )( P )( P ) Hyp − tetramer was compared to that of the ( P )( P )( M )( M ) and ( P )( M )( P )( M ) racemic aggregates. The illustrative ball-and-stick models of the ( P )( P )( P )( P ) and ( P )( P )( M )( M ) Hyp − tetramers are shown in Figure .…”

“…9 The enantiomers of Hyp were investigated theoretically and experimentally by other authors. 9,[20][21][22] In the present work, the structure of the homochiral (P)(P)(P)(P) Hyptetramer was compared to that of the (P)(P)(M)(M) and (P)(M)(P)(M) racemic aggregates. The illustrative ball-and-stick models of the (P)(P)(P)(P) and (P)(P)(M)(M) Hyptetramers are shown in Figure 2.…”