Chemical and physical models for the emergence of biological homochirality.

The past several decades have witnessed the development of a number of different experimental approaches to help understand how the homochirality of biological molecules might have evolved in a prebiotic world. This chapter reviews chemical and physical models with a special focus on recent developments in attrition-enhanced deracemization of conglomerates, a process that combines solution phase chemical interconversion of enantiomers with thermodynamic and kinetic considerations of solubility, crystal growth, and dissolution.

Enantiomers of dimethyl [(2E)-1,3-diphenylprop-2-en-1-yl]propanedioate resulting from allylic alkylation reaction: elution order on major high-performance liquid chromatography chiral columns.

Asymmetric allylic alkylation leading to dimethyl [(2E)-1,3-diphenylprop-2-en-1-yl]propanedioate 1 is a privileged reaction which has been considered in more than 800 references from 1985 to early 2012. This paper thus begins with a thorough review of the literature with a particular focus on the way the ee's and absolute configuration of the prevailing enantiomer were claimed and reported by the authors. In a large majority of articles chiral chromatography is used for ee's determination.

XRD and VCD: a marriage of love or convenience? Honeymoon around a cyclic urea derivative.

The structures and absolute configurations of the enantiomers (3aR,8aR)-2,2-dimethyl-4,4,8,8-tetraphenyl-4,5,6,7,8,8a-hexahydro-3aH-1,3-dioxolo[4,5-e][1,3]diazepin-6-one 0.33-hydrate, C(32)H(30)N(2)O(3)·0.33H(2)O, (Ia), and (3aS,8aS)-2,2-dimethyl-4,4,8,8-tetraphenyl-4,5,6,7,8,8a-hexahydro-3aH-1,3-dioxolo[4,5-e][1,3]diazepin-6-one 0.

Conformational equilibria of TADDOL-s in solution investigated by vibrational circular dichroism.

Six enantiomeric pairs of TADDOL-s gathered in two series with either methyl (series A) or phenyl (series B) substituent in 2-position of the dioxolane ring were studied by vibrational circular dichroism (VCD). Experimental IR and VCD spectra associated with density functional theory (DFT) calculations showed that the two series exhibit quite different conformations in solution. In series A, the conformer with anti C-O bonds and stabilized by intramolecular OH.

HPLC on chiral support with polarimetric detection: application to conglomerate discovery.

In conglomerates, each single crystal contains only one of the two possible enantiomeric forms--either dextrorotatory or levorotatory. The analysis of a single crystal by liquid chromatography on chiral support associated with chiroptical detection is a very efficient tool to reveal the occurrence of a conglomerate. In terms of rapidity and easiness, this method compares favorably with the classical methods used to show this occurrence.