Chemical and chemotaxonomical studies of ferns. LIV. Pterosin derivatives of the genus Microlepia (Pteridaceae).

From the fronds of five pteridaceous ferns [Microlepia speluncae (L). MOORE, M. trapeziformis (ROXB.) KUHN, M. obtusiloba HAYATA, M. substrigosa TAGAWA and M. strigosa (THUNB.) PRESL], several 1-indanone-type sesquiterpenes (pterosins and pterosides) were isolated. Four of them, isolated from M. speluncae were new and were assigned the structures 13-hydroxy-3 (R)-pterosin D (V), 13-hydroxy-3 (R)-pterosin D 3-O-α-L-arabinopyranoside (VI), 3 (R)-pterosin D 3-O-α-L-arabinopyranoside (VIII) and 2 (R), 3 (R)-pterosin D 3-O-α-L-arabinopyranoside (XI). The structures were elucidated mainly by spectroscopic methods. Compound V was named spelosin. The investigation of two other species, M. calvescens (WALL.) PRESL and M. okamotoi TAGAWA, gave no identifiable compounds, of this type.