Host–Guest Assembly of a Molecular Reporter with Chiral Cyanohydrins for Assignment of Absolute Stereochemistry

Abstract

The absolute stereochemistry of cyanohydrins, derived from ketones and aldehydes, is obtained routinely, in a microscale and derivatization-free manner, upon their complexation with Zn-MAPOL, a zincated porphyrin host with a binding pocket comprised of a biphenol core. The host-guest complex leads to observable exciton-coupled circular dichroism (ECCD), the sign of which is easily correlated to the absolute stereochemistry of the bound cyanohydrin. A working model, based on the ECCD signal of cyanohydrins with known configuration, is proposed.

Di(1‐naphthyl) methanol ester of carboxylic acids for absolute stereochemical determination

“…The best solution for a particular functional group, or a subfamily of molecules, is not necessarily the best choice for another, and thus, the continual optimization of old methods and new creative approaches are needed. Amongst the many different chiroptical techniques, exciton‐coupled circular dichroism (ECCD), a method based on the through space electronic coupling between two or more nonconjugated chromophores, has enjoyed great success as a result of its ability to directly correlate the sign of the ECCD signal to the helicity of the coupling chromophores . Nuclear magnetic resonance (NMR) methods are also widely used in stereochemical determinations, although chemical derivatizations are necessary to convert enantiomers to diastereomers.…”

A chiroptical approach for the absolute stereochemical determination of P-stereogenic centers

“…hydrogen bonding with phenolic functionality and complexation with the zinc metal center (Figure 1). Although for cyanohydrin both hydrogen bonding and ligand coordination to Zn metallo-center was necessary, 9 chiral sulfoxides required coordination of the sulfoxide oxygen atom to the Zn metal to induce helicity of Zn-MAPOL 2 (Figure 1). 10 Intrigued by the results observed with sulfoxides we realized that a similar approach might provide an effective chiroptical solution for the absolute stereochemical assignment of P-chiral phosphorus oxides.…”

Сhiral and Racemic Fields Concept for Understanding of the Homochirality Origin, Asymmetric Catalysis, Chiral Superstructure Formation from Achiral Molecules, and B-Z DNA Conformational Transition

“…The length of the chain the inductor and porphyrin group separating can exceed 13 single and double bonds 173 . In the absence of a chiral inductor, such structure is used to study molecular chirality of chiral bidentate guest molecules by circular dichroism of metalloporphyrin hosts as a sensor of chirality [202][203][204][205][206][207]. End porphyrin groups can be located at a considerable distance from each other in formulations such as dibenzo30-crown-10 skeleton 51 [208].…”