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The versatility of the natural products (2S,3S)- and (2S,3R)-3-hydroxy-5-oxotetrahydrofuran-2,3-dicarboxylic acids (1 and 2), isolated in large amounts from tropical plant sources, has been demonstrated by the construction of 3-substituted and 3,4-disubstituted chiral pyrrolidine-2,5-diones. The absolute configurations of chiral pyrrolidine-2,5-diones have been ascertained using chiroptical spectroscopic methods and/or single-crystal XRD data. A combination of different reaction strategies delivering a diverse matrix of fused heterocyclic ring systems is presented. The pyrrolo­[2,1-a]­isoquinoline alkaloid (+)-crispine A possesses a wide range of pharmacological activities including antidepressant, antiplatelet, antileukemic, and anticancer activities. The analogues of indolizino­[8,7-b]­indole alkaloids (+)- and (−)-harmicine show strong antileishmanial, antinociceptive, PDE5-inhibitory, antimalarial, and antiviral activities. The bicyclic furo­[2,3-b]­pyrrolo skeleton is present in many natural products. Thus, the uniqueness of relatively cheap, naturally occurring chiral 2-hydroxycitric acid lactones as chirons has been demonstrated by the construction of some important molecular skeletons that are otherwise difficult to synthesize.

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Small chiral molecules are excellent candidates to push the boundaries of enantiodiscrimination analytical techniques. Here is reported the synthesis of two new deuterated chiral probes, (R)-and (S)-[ 2 H]-ethyl tosylate obtained with high ee's. Due to their crypto-optically active properties, the discrimination of each enantiomer is challenging. While their enantiopurity is determined by 2 H-NMR in chiral anisotropic media, their identification was performed by combining quantum chemical calculations and vibrational circular dichroism analysis.

Hexahydrocurcumin (HHC) and octahydrocurcumin (OHC) were synthesized, and their enantiomers were separated using supercritical fluid chromatography. The absolute configurations (ACs) of HHC and OHC were independently determined using experimental measurements and quantum theoretical predictions of vibrational circular dichroism, electronic circular dichroism, and optical rotatory dispersion. These studies lead to AC assignments of (À)-(R)-HHC and (+)-(R,R)-OHC. The AC of OHC is further confirmed by its structure determined from single crystal x-ray diffraction.

Triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) are cyclic peroxides that exhibit atropisomerism resulting from restricted rotation around three peroxide bonds. As a result, one pair of enantiomers with D 3 symmetry and another pair of enantiomers with C 2 symmetry can be identified. Previous studies, based on mass spectrometry data and computational results, have shown that conformations of TATP with D 3 and C 2 symmetry can be isolated. Assuming that enantiomer samples of TATP and HMTD can be obtained with sufficient enantiopurity, we investigated their chiroptical properties, namely, optical rotatory dispersion (ORD), vibrational circular dichroism (VCD), and Raman optical activity (VROA). ORD curves and VCD spectra are seen to be very similar for D 3 -and C 2 -symmetric atropisomers with the same overall helicity. Predicted VROA results, however, show significant differences between D 3 -and C 2 -symmetric atropisomers with the same overall helicity. The D 3 -symmetric atropisomer is predicted to exhibit considerably larger magnitude vibrational optical activity signals than the C 2symmetric atropisomer.explosives, hexamethylene triperoxide diamine, optical rotatory dispersion, Raman optical activity, transition states, triacetone triperoxide, vibrational circular dichroism [This article is part of the Special issue: Chiral Materials. See the first articles for this special issue previously published in Volumes 34:12, 35:2 and 35:3. More special articles will be found in this issue as well as in those to come.]

The experimental vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectra were measured for the enantiomers of [1]rotaxane 1. These experimental spectra have been analyzed using predicted VCD and ECD spectra for (S, Rmp) or (S, Smp) diastereomers using density functional theory. This comparison allowed for a definitive assignment of the absolute configuration of 1.