New phenanthrene derivatives from Maxillaria densa

Two new phenanthrene derivatives, 2,5-dihydroxy-3,4-dimethoxyphenanthrene ( 1) and 9,10-dihydro-2,5-dihydroxy-3,4-dimethoxyphenanthrene (2), were isola ted from an extract prepared from the whole plant of the orchid Maxillaria densa with spasmolytic activity. In addition, four known compounds, namely 2,7-dihydroxy-3,4-dimethoxyphenanthrene, 9,10-dihydro-2,7-dihydroxy-3,4-dim ethoxyphenanthrene (3), 2,5-dihydroxy-3,4,9-trimethoxyphe-nanthrene and 2,7 -dihydroxy-3,4,9-trimethoxyphenanthrene, were obtained. The structures of t he isolated compounds were elucidated by spectroscopic methods. In the case of phenanthrene derivatives 1 and 3, the structures were unambiguously ass igned by X-ray analysis.