[Phytochemical study of liverworts Conocephalum conicum and Chiloscyphus polyanthos]

Four hundred samples of Conocephalum conicum, collected in various places have been analyzed by GC-MS. This resulted in the presence of three chemo-types of C. conicum. One of them elaborate (-)-sabinene (type-I) as a major compound. The other two types characteristically contained (+)-bornyl acetate (type-II) and methyl cinnamate (type-III) as major constituent respectively. The structures of three new monoterpenic esters, isolated from the ether extract of C. conicum (type-I and/or II) have been established by chemical and spectral means. They were shown to be monoterpenic esters of (+)-borneol and p-coumaric acid derivatives. The ether extract of the liverwort Chiloscyphus polyanthos afforded sesquiterpenoids which are enantiomeric to those found in another liverwort Lepidozia vitrea. The absolute configurations of the sesquiterpenoids found in the C. polyanthos were determined by spectroscopic evidence, chemical derivatization and/or x-ray crystallographic analysis. 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 (+)-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.