Biologically active clerodane-type diterpene alcohol and its glycosides from the root-stalks of ferns

Abstract

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 β-D-glucosylation-shift rule and by measurement of ¹³C NMR chemical shifts, respectively. Further, two glycosides showing growth inhibition were also isolated from D. pedata and they were characterised as the 13-O-β-L-fucopyranosyl-(1 → 2)-α-L-rhamnopyranoside 3 and 13-O-α-L-fuoopyranosyl-(1 → 2)-[α-L-rhamnopyranosyl-(1 → 3)]-α-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-β-L-fucopyranosyl-6-O-α-L-rhamnopyranosylcleroda-3,14-diene-6,13-diol 2.