Four pentacyclic guanidine derivatives (crambescidin 800 [5], crambescidin 816 [6], isocrambescidin 800 [9], and crambine [10]) related to ptilomycalin A [11] have been isolated from the Mediterranean sponge Crambe crambe. Isocrambescidin 800 and crambidine are new derivatives, the structures of which have been determined on the basis of their spectral properties. The absolute configuration of crambescidin 816 at the stereogenic center C-43 has been determined by applying Mosher's method. Pharmacological and biological activities of the Crambe crambe alkaloids are reported. In particular, crambescidin 816 was found to have a potent Ca++ antagonist effect and to inhibit the acetylcholine-induced contraction of guinea pig ileum at very low concentrations.

Dactylolide (1), a new cytotoxic 20-membered macrolide, was isolated from a marine sponge of the genus Dactylospongia collected off the coast of the Vanuatu islands. It co-occurred with other known bioactive macrolides: latrunculin A (2), laulimalide (3), isolaulimalide (4) and with the anthel- [a]

Chemical investigation of the Et(2)O extract of the marine sponge Rhaphisia lacazei resulted in the isolation of 13 pure bisindole alkaloids (1-13). Compounds (1-6) belong to the class of topsentins and have already been described. Compounds 7-13 are new products, closely related to the class of hamacanthins. The major compounds 1-3 were tested in vitro for antitumor activity; compounds 2 and 3 showed antiproliferative activity against human bronchopulmonary cancer cells (NSCLC-N6) with an IC(50) of 12 and 6.3 microg/mL, respectively.

Chromatin remodeling is a fundamental phenomenon in the life of eukaryotic cells, bearing implications to numerous physiological and pathological phenomena. This review outlines the chemistry of natural and synthetic agents endowed with the ability to interfere with such biological function, with a particular emphasis on histone deacetylase (HDAC) inhibitors. Other aspects covered in this article comprise structure activity relationships (SAR) and modes of action at molecular level, including the description of crystal structures of enzyme-inhibitor complexes.

Since L-fucose is known to be a constituent of brown seaweed, Dfucose obtained here was determined by the exciton-split c.d. curve of methyl 2,3,4-tri-O-@-bromobenzoyl)-a-~-fuc0pyran0side [c.d.: 236/254, A& -26.8/+98.7, A + 125.5; calc. A: + 140 (ref. 19)].