A revision of the positive sign of the optical rotation and its maximum value of α-eudesmol

The ether extract of the liverwort Porella perrottetiana afforded (-)-alpha-eudesmol, which showed an opposite sign of the optical rotation to that found in higher plants. Present work on the absolute configuration and an optical purity of (-)-alpha-eudesmol strongly suggested that the positive values (e.g. + 28.5 degrees) described in many previous papers should be revised. Since the absolute configuration of (-)-alpha-eudesmol was identical to that of (+)-beta-eudesmol found in the higher plants, it was apparent that the expression of the positive sign might be revised to (-)-alpha-eudesmol. The optical purity, reconfirmation of the absolute configuration and synthesis of (-)-alpha-eudesmol will be discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.