MOLECULAR ASYMMETRY OF MACROCYCLIC BIS(BIBENZYL)S, NATURAL PRODUCTS FROM LIVERWORT SPECIES

Abstract Conformation of marchantin H triacetate (1), a bis(diarylether)-type macrocyclic bis(bibenzyl), was studied by molecular mechanics calculations. The most stable enantiomeric conformations were found, but no direct path for the interconversion could be detected. Fast non-direct interconversion, however, was confirmed by chiral HPLC. Ring inversion of compounds containing the biphenyl moiety was investigated on plagiochin C tribenzyl ether (3). Enantiomers in both cases were separated by chiral HPLC and their CD spectra measured on-line. Conformational analysis of 3 was performed by molecular mechanics conformational search. Configuration of the minimum energy enantiomeric conformations was established by calculation of the rotatory strengths at the INDO/S level.