Speradines B-E, Four Novel Tetracyclic Oxindole Alkaloids from the Marine-Derived Fungus Aspergillus oryzae

Abstract

Four novel tetracyclic oxindole alkaloids, namely, speradines B (1), C(2), D (3), and E (4) were isolated from the marine-derived fungus Aspergillus oryzae. The structures of these compounds without the absolute configurations were elucidated through 1D and 2D nuclear magnetic resonance and high-resolution mass spectrometric analyses. Among these compounds, 1 and 4 showed weak cytotoxic effects on the HeLa cell line.Indole-terpenes are fungal and bacterial secondary metabolites with unique biological activities such as inhibitory activity of calcium-activated potassium channels, 1 antitumor activity, 2 tremorgenic activity, 3 potent and selective progesterone receptor agonistic activity, 4 and anti-MRSA activity. 5 Cyclopiazonic acid (CPA)-type alkaloids are one important group of indole-terpenes, and they usually contain three structural units: an indole, a dimethylallyl (DMA), and two acetic acids. Only six analogous natural products have been reported to date, including α-cyclopiazonic acid, 6 iso-α-cyclopiazonic acid, 7 β-cyclopiazonic acid, 6 α-acetyl-γ-(β-indolyl)methyl-tetramic acid, 8 speradine A, 9 and 3-hydroxyl speradine A. 10 In our search for novel anticancer compounds, 11 a strain of Aspergillus oryzae showed significant cytotoxic activity. Further chemical study led to isolation and structure elucidation of four new

Rhodium(III)-Catalyzed C–H Functionalization in Water for Isoindolin-1-one Synthesis

“…Isoindolin-1-ones have been found in many natural or bioactive compounds (Figure ). Thus, the synthesis of this class of compounds has elicited considerable interest, and various synthetic methods have been developed. Known approaches are (i) lactamization of o -azidomethyl or o -aminomethyl benzoic acids, (ii) intramolecular Heck cyclization of N -alkenyl/alkynyl o -halobenzamides, (iii) C–X aminocarbonylation of o -halobenzylamines, (iv) cyclization of o -alkenyl (or o -alkynyl) benzamides, and (v) radical cyclization of 2-azidomethyl benzoyl radicals or N -benzyl carbamoyl radicals .…”