BIOLOGICALLY-ACTIVE CLERODANE-TYPE DITERPENE ALCOHOL AND ITS GLYCOSIDES FROM THE ROOT-STALKS OF FERNS

A diterpene alcohol showing a growth inhibition of lettuce was isolated from the root-stalks of Dicranopteris pedata and Gleichenia japonica. Its structure was determined to be (6S,13S)-cleroda-3,14-diene-6,13-diol 1, an aglycone of the two glycosides previously isolated from G. japonica; the chirality at both C-6 and C-13 was assigned as S by application of the beta-D-glucosylation-shift rule and by measurement of C-13 NMR chemical shifts, respectively. Further, two glycosides showing growth inhibition were also isolated from D. pedata and they were characterised as the 13-O-beta-L-fucopyranosyl-(1 --> 2)-alpha-L-rhamnopyranoside 3 and 13-O-alpha-L-fucopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1 --> 3)]-alpha-L-rhamnopyranoside 4 of the diterpene alcohol; the above assignment of the chirality at C-13 was established by measurement of nuclear Overhauser enhancement for the trisaccharide. In addition, a glycoside showing growth acceleration was also isolated and its structure was determined to be (6S,13S)-13-O-beta-L-fucopyranosyl-6-O-alpha-L-rhamnopyranosylcleroda-3,14-diene-6,13-diol 2.