Tetranorclerodanes and clerodane-type diterpene glycosides from Dicranopteris dichotoma

The acetone extract of Dicranopteris dichotoma afforded two new tetranorclerodanes, 18-hydroxyaylthonic acid (1) and 18-oxo-aylthonic acid (2), and four new clerodane-type diterpene glycosides, (6S,13S)-6-O-6-O-acetyl-beta-d-glucopyranosyl-(1-->4)-alpha-l-rhamnopyranosyl]cleroda-3,14-dien-13-ol (3), (6S,13S)-6-O-4-O-acetyl-beta-d-glucopyranosyl-(1-->4)-alpha-l-rhamnopyranosyl]cleroda-3,14-dien-13-ol (4), 6-O-6-O-acetyl-beta-d-glucopyranos-yl-(1-->4)-alpha-l-rhamnopyranosyl]-(13E)-cleroda-3,13-dien-15-ol (5), and 6-O-beta-d-glucopyranosyl]-(1-->4)-alpha-l-rhamnopyranosyl-(13E)-cleroda-3,13-dien-15-ol (6), together with two known compounds, aylthonic acid (7) and (6S,13S)-cleroda-3,14-diene-6,13-diol (8). The structures of these new compounds were established by a combination of 1D and 2D NMR techniques, MS, and acid hydrolysis. Compound 8 showed modest anti-HIV-1 activity.