it has two spirofused six-membered ketal ring systems in place of the more commonly encountered spiroketal involving six-and fixe-membered rings. The presence of two fused tetrahydropyran rings (D, E) is also unique.Acanthifolicin exhibits ED50's of 2.8 X 10"4, 2.1 X 10"3, and 3.9 X 10"3 9mcg/mL, respectively, against P388, KB, and L1210 cell lines. In vivo antitumor tests and other biological activity evaluation are in progress.Efforts are under way to isolate microorganisms associated with P. acanthifolium that may produce acanthifolicin. In this connection it may be noted that a macrolide polyether antibiotic, aplasmomycin, has been isolated from a marine bacterium.10 Acknowledgment. This investigation was supported by Grant CA-17256, CA-17562, and Contract N01-CM-67108 awarded by the National Cancer Institute, DHEW. We thank Ms. Lin Craft for sponge identification and assistance in sample collection. 360-MHz NMR spectra were obtained at the Purdue Biochemical Magnetic Resonance Laboratory supported by NIH Grant RR 01077. Supplementary Material Available: A listing of the final parameters, bond angles, torsion angles, structure factors, bond lengths, and Bijvoet differences is available (40 pages). Ordering information is given on any current masthead page.

Four novel bisulfide bromotyrosine derivatives, psammaplins E (9), F (10), G (11), and H (12), and two new bromotyrosine derivatives, psammaplins I (13) and J (14), were isolated from the sponge Pseudoceratina purpurea, along with known psammaplins A (4), B (6), C (7), and D (8) and bisaprasin (5). The structures of psammaplins E (9) and F (10), which each contain an oxalyl group rarely found in marine organisms, were determined by spectroscopic analysis. Compounds 4, 5, and 10 are potent histone deacetylase inhibitors and also show mild cytotoxicity. Furthermore, compounds 4, 5, and 11 are potent DNA methyltransferase inhibitors. The biogenetic pathway previously proposed for the psammaplins class is also revisited.

Two new isomeric brominated tyrosine metabolites containing disulfide linkages have been isolated from an unidentified sponge from Guam. Their structures were determined primarily from and 13C NMR data.(3-Bromo-4-hydroxyphenyl)acetonitrile was also isolated.

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