title: Central-to-axial chirality transfer revealed by liquid crystals: a combined experimental and computational approach for the determination of absolute configuration of carboxylic acids with an α chirality centre.
abstract: The conversion into 6,7-dihydro-5H-dibenz[c,e]azepine (DAZ) N-protected amides is a viable route for the determination of the absolute configuration of chiral 2-substituted carboxylic acids. The biphenyl moiety of DAZ, besides being a probe of chirality for the electronic circular dichroism (ECD) spectroscopy, makes these systems suitable for configuration assignment by exploiting the chirality amplification which occurs in nematic liquid crystals. To assess the reliability of the liquid crystal method in detecting the absolute stereochemistry of chiral amides bound to a biphenyl group, we measured the helical twisting power of a series of DAZ-N-protected amides and compared these data with the results obtained from ECD measurements. We will show that the liquid crystal method, corroborated by HTP predictions, is trustworthy with our biphenyl derivatives, even when ECD spectra are ambiguous for the presence of aryl moieties displaying strong UV absorptions in the same range of the biphenyl chromophore.
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Padova, Via F. Marzolo 1, I-35131 Padova, Italy.
authors.forename: Alberta
authors.initials: A
authors.lastname: Ferrarini
authors.forename: Fiammetta
authors.initials: F
authors.lastname: Ferroni
authors.forename: Silvia
authors.initials: S
authors.lastname: Pieraccini
authors.forename: Carlo
authors.initials: C
authors.lastname: Rosini
authors.forename: Stefano
authors.initials: S
authors.lastname: Superchi
authors.forename: Gian Piero
authors.initials: GP
authors.lastname: Spada
mesh_terms: D001713:Biphenyl Compounds / Q000737:chemistry*; D002264:Carboxylic Acids / Q000138:chemical synthesis* / Q000737:chemistry*; D002942:Circular Dichroism / Q000379:methods*; D003198:Computer Simulation; D050866:Liquid Crystals; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D013056:Spectrophotometry, Ultraviolet / Q000379:methods
chemical_list: D001713:Biphenyl Compounds; D002264:Carboxylic Acids