Toluene Dioxygenase‐Catalyzed Synthesis of cis‐Dihydrodiol Metabolites from 2‐Substituted Naphthalene Substrates: Assignments of Absolute Configurations and Conformations from Circular Dichroism and Optical Rotation Measurements

Abstract

cis-Dihydrodiol metabolites have been isolated from naphthalene and six 2-substituted naphthalene substrates. Their structures and absolute configurations have been determined by a combination of calculated (TDDFT) and experimentally based circular dichroism (CD) and optical rotation (OR) methods. The "inverse" styrene helicity rule is shown to be incorrect for the interpretation of the CD spectra of cis-dihydrodiols. A striking conclusion is that CD spectra correlate directly with the helicity of the styrene chromophore: that is, the sign of the long-wavelength Cotton effect is identical with the sign of styrene torsion angle, whereas the OR sign is dependent on the absolute configuration of the allylic carbon atom. The results demonstrate that a predictive model previously used for the determination of preferred regio- and stereoselectivity associated with TDO-catalyzed cis-dihydroxylation of substituted benzene substrates can now be successfully extended to substituted naphthalene substrates.