Sensing Remote Chirality: Stereochemical Determination of β‐, γ‐, and δ‐Chiral Carboxylic Acids

Abstract

Determining the absolute stereochemisty of small molecules bearing remote nonfunctionalizable stereocenters is ac hallenging task. Presented is as olution in whicha ppropriately substituted bis(porphyrin) tweezers are used. Complexation of asuitably derivatized b-, g-, or d-chiral carboxylic acid to the tweezer induces ap redictable helicity of the bis(porphyrin), which is detected as ab isignate Cotton Effect (ECCD). The sign of the ECCD curve is correlated with the absolute stereochemistry of the substrate based on the derived working mnemonics in apredictable manner.

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.…”