Bioassay-guided fractionation of the organic extract from a culture of Phomopsis longicolla, an endophytic fungus of the endangered mint Dicerandra frutescens, led to the isolation of dicerandrols A, B, and C. Extensive NMR and HRFABMS experiments were used to identify these new yellow antibiotic and cytotoxic compounds as 2,2'-dimeric tetrahydroxanthones.

Dicerandrols, new antibiotic and cytotoxic dimers produced by the fungus Phomopsis longicolla isolated from an endangered mint.

Chemical investigation of the Philippine ascidian Perophora namei has resulted in the isolation of a novel polycyclic alkaloid, perophoramidine (1). The structure of 1 was determined by the interpretation of 1D/2D NMR and MS data. Dehalogenation of perophoramidine (1) by ammonium formate catalyzed transfer hydrogenation confirmed the type and number of halogen atoms present in 1.

Isolation, structure determination, and biological activity of a novel alkaloid, perophoramidine, from the Philippine ascidian Perophora namei.

Two new metabolites, named halipeptins A and B, have been isolated from the marine sponge Haliclona sp. Their structures were determined by extensive use of one- and two-dimensional NMR experiments, mass spectrometry, and UV and IR spectroscopy. Halipeptin A is a novel 17-membered cyclic depsipeptide, consisting of five residues including two alanines (with l stereochemistry) and three new residues that appear to be previously undescribed from natural sources:  1,2-oxazetidine-4-methyl-4-carboxylic acid, 3-hydroxy-2,2,4-trimethyl-7-methoxydecanoic acid (HTMMD), and N-methyl-δ-hydroxyisoleucine. The HTMMD residue is substituted with 3-hydroxy-2,2,4-trimethyl-7-hydroxydecanoic acid in halipeptin B. Halipeptin A was found to possess very potent anti-inflammatory activity in vivo, causing about 60% inhibition of edema in mice at the dose of 300 μg/kg (i.p.).

Halipeptins A and B: two novel potent anti-inflammatory cyclic depsipeptides from the Vanuatu marine sponge Haliclona species.

Laurus nobilis L. leaves are widely used in cooking and in folk medicine. Five new megastigmane glucosides (2-4, 7, and 9) named laurosides A-E and a new phenolic glucoside 12 were isolated from the methanolic extract of L. nobilis L. leaves, along with 10 known components: megastigmane (5), megastigmane glucosides (1, 6, 8, 10, and 11), aromatic compounds (13 and 14), and flavonoids (15 and 16). The structures and relative stereochemistry have been elucidated by one- and two-dimensional nuclear magnetic resonance experiments ((1)H and (13)C NMR, DEPT, correlation spectroscopy, heteronuclear multiple quantum correlation, heteronuclear multiple bond correlation, and nuclear Overhauser enhancement spectroscopy) and by chemical derivatization. The effect of isolated compounds on nitric oxide production in lipopolysaccharide-activated murine macrophages were examined.

Megastigmane and phenolic components from Laurus nobilis L. leaves and their inhibitory effects on nitric oxide production.

Four cyclic peptides, kapakahines A−D, were isolated from the marine sponge Cribrochalina olemda. Their structures including complete stereochemistry were elucidated by spectral analysis and chemical degradation. The unique structural feature of these peptides is the lack of an amide linkage between two tryptophan residues. Instead the ring is closed by a bond from the indole nitrogen of Trp-1 to the β-carbon of Trp-2.

V. P. Vitullo

Papers

Intramolecular electrostatic stabilization of an SN1 transition state