Elucidation of the absolute configuration of knipholone and knipholone anthrone by quantum chemical CD calculations

The absolute configuration of knipholone, an axially chiral phenylanthraqui none from Kniphofia, Bulbine, and Bulbinella species, has been established as M by quantum chemical CD calculations. For further evidence, the absolut e stereostructure of the related compound knipholone anthrone, which has a significantly different chromophor, was likewise elucidated. The fact that both natural biaryls compounds were independently attributed the same absol ute configuration, underlines the reliability of the results and the value of the applied method. (C) 1999 Elsevier Science Ltd. All rights reserved.