Trikentramides A–D, Indole Alkaloids from the Australian Sponge Trikentrion flabelliforme

• Published in: Journal of natural products (Washington, D.C.) Vol. 76; no. 11; pp. 2100 - 2105
• Main Authors: Khokhar, Shahan, Feng, Yunjiang, Campitelli, Marc R, Quinn, Ronald J, Hooper, John N. A, Ekins, Merrick G, Davis, Rohan A
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society and American Society of Pharmacognosy 22.11.2013; Amer Chemical Soc
• Subjects: Animals; Australia; Chemistry, Medicinal; Indole Alkaloids - chemistry; Indole Alkaloids - isolation & purification; Life Sciences & Biomedicine; Marine Biology; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Oxidation-Reduction; Pharmacology & Pharmacy; Plant Sciences; Porifera - chemistry; Science & Technology; Australia; ORGANIC-MOLECULES; LOEVE; CHEMICAL-SHIFTS; STEREOCHEMISTRY; ENERGIES; SPECTRA; PRINCIPLES; PREDICTION
• ISSN: 0163-3864; 1520-6025
• DOI: 10.1021/np400617h

Chemical investigations of two specimens of Trikentrion flabelliforme collected from Australian waters have resulted in the identification of four new indole alkaloids, trikentramides A–D (9–12). The planar chemical structures for 9–12 were established following analysis of 1D/2D NMR and MS data. The relative configurations for 9–12 were determined following the comparison of 1H NMR data with data previously reported for related natural products. The application of a quantum mechanical modeling method, density functional theory, confirmed the relative configurations and also validated the downfield carbon chemical shift observed for one of the quaternary carbons (C-5a) in the cyclopenta[g]indole series. The indole-2,3-dione motif present in trikentramides A–C is rare in nature, and this is the first report of these oxidized indole derivatives from a marine sponge.