Dehydrodecalin derivative from marine isolate of the fungus Wardomyces inflatus

Abstract

In connection with the program to discover biologically active compounds in extracts of marine isolates of microscopic fungi, we tested 1000 strains of marine fungi isolated from marine sediments of Sakhalin Bay for the presence in their extracts of compounds with antibiotic activity that were active in early embryogenesis of the sea urchin Strongylocentrotus intermedius. One of them, Wardomyces inflatus (Marchal) Hennebert, synthesized such compounds. This fungus is usually parasitic on terrestrial plants [1, 2] and was isolated by us for the first time from deep (50 m) marine sediments. Mycelium of the fungus with medium was extracted twice with EtOAc. The extract was evaporated. The solid was dissolved in EtOH:H 2 O (1:4) and extracted (2×) successively with hexane, CHCl 3 , and BuOH. The CHCl 3 extract was evaporated in vacuo. The dry solid (700 mg) was chromatographed over a column (25 × 2 cm) of SiO 2 . Compound 1 (27 mg) was eluted by hexane:EtOAc (85:15). The UV spectrum of the compound had no absorption bands. Its IR spectrum showed absorption bands characteristic of hydroxyls (3621, 3568 cm –1 ). The PMR and 13 C NMR spectra of 1 (Table 1) was consistent with two quaternary C atoms (δ C 52.6, C-1; 215.7, C-9) and eight methines (δ H 1.94–δ C 52.3, C-2; δ H 5.70–δ C 123.9, C-3; δ H 6.0–δ C 126.1, C-4; δ H 2.14–δ C 39.0, C-4a; δ H 3.43–δ C 75.3, C-5; δ H 4.04–δ C 69.6, C-6; δ H 1.74–δ C 30.5, C-8; δ H 1.93–δ C 43.0, C-8a; δ H 1.12–δ C 37.1, C-1′), two of which were bound to C-5 and C-6, which were oxygenated, and two of which were located on the C-3–C-4 double bond. The position of the resonances for the C-3 and C-4 protons and their SSCC indicated that they were situated cis to each other on the double bond. Besides these resonances, spectra of 1 contained resonances for four methyls (δ H 0.59–δ C 22.4, CH 3 -12; δ H 0.75–δ C 12.5, CH 3 -3′; δ H 0.93–δ C 19.2, CH 3 -4′; δ H 1.25–δ C 19.4, CH 3 -13), the multiplicity of which indicated that one of them was bound to a quaternary C atom; two, to a tertiary; and one, to a secondary. The chemical structure was determined from the 1 H– 1 H COSY and HSQC spectra incorporating HMBC correlations