CONSTITUENTS OF MARINE PLANTS .30. THE ABSOLUTE-CONFIGURATIONS OF HALOGENATED CHAMIGRENE DERIVATIVES FROM THE MARINE ALGA, LAURENCIA-GLANDULIFERA KUTZING

The absolute configurations of halogenated chamigrene derivatives, isolated from L. glandulifera Kützing, 10-bromo-3,4-epoxy-α-chamigrene (1), glanduliferol (2), 10-bromo-α-chamigren-4-one (3), 4,10-dibromo-3-chloro-α-chamigrene (4) and 10-bromo-α-chamigrene (5), have been determined by X-ray diffraction analysis of 1 and subsequently, by relating 2, 3, 4 and 5 to 1 with the chemical methods. In addition, the absolute configuration of (-)-α-chamigrene (6), yielded on the process of the above chemical transformation, has been elucidated. © 1979.