title: Isolation and structure assignments of rostratins A-D, cytotoxic disulfides produced by the marine-derived fungus Exserohilum rostratum.
abstract: Four new cytotoxic disulfides, rostratins A-D (1-4), were isolated from the whole broth of the marine-derived fungus Exserohilum rostratum (Drechsler), a fungal strain found associated with a marine cyanobacterial mat. The structures of these cyclic dipeptides were established through chemical degradation and a variety of two-dimensional NMR techniques. The absolute configurations of the rostratins were determined by the modified Mosher method. In the case of the polyhydroxylated compound 1 and the mercaptol 4, regioselective acylation was achieved by modulating the reaction temperature while monitoring the progress of the reaction by 1H NMR. Rostratins A, B, C, and D showed in vitro cytotoxicity against human colon carcinoma (HCT-116) with IC50 values of 8.5, 1.9, 0.76, and 16.5 microg/mL, respectively.
authors.affiliation: Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0204, USA.
authors.forename: Ren Xiang
authors.initials: RX
authors.lastname: Tan
authors.forename: Paul R
authors.initials: PR
authors.lastname: Jensen
authors.forename: Philip G
authors.initials: PG
authors.lastname: Williams
authors.forename: William
authors.initials: W
authors.lastname: Fenical
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D000458:Cyanobacteria; D004220:Disulfides / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D004354:Drug Screening Assays, Antitumor; D006254:Hawaii; D006801:Humans; D020128:Inhibitory Concentration 50; D003904:Mitosporic Fungi / Q000737:chemistry*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010456:Peptides, Cyclic / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D010648:Phenylacetates / Q000737:chemistry; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D004220:Disulfides; D010456:Peptides, Cyclic; D010648:Phenylacetates; C101363:alpha-methoxy-alpha-trifluoromethylphenylacetyl chloride