The absolute axial configurations of knipholone and knipholone anthrone by TDDFT and DFT/MRCI CD calculations: a revision

摘要: Triggered by a seemingly inconsistent twisting direction in the atroposelective ring cleavage reaction of biaryl lactones using ‘lactone concept’, absolute axial configurations most important phenylanthraquinones, knipholone (1), and anthrone (2) were reassigned on basis renewed quantum chemical circular dichroism (CD) calculations advanced, higher-level methods, viz. time-dependent DFT (TDDFT) multireference configurational interaction approach (DFT/MRCI). Additional confirmation new assignment 1 2 was achieved their stereochemically unambiguous interconversion, further corroborated transformation into an ‘leuco’ phenylanthracene derivative 3, i.e., compound with substantially different chromophore, whose configuration independently assigned again CD calculations. Accordingly, dextrorotatory enantiomer knipholone, (+)-1, its anthrone, (+)-2, has P-configuration, while laevorotatory forms, (−)-1 (−)-2 (which likewise exist nature), are M-configured. From this assignment, stereostructures whole series naturally occurring phenylanthraquinones may now be deduced.