Reisolation and Structure Revision of Asperspiropene A

Abstract

Asperspiropene A was originally reported to have a unique 1,8-dioxaspiro[4.5]­decane skeleton. During the course of our ongoing research for novel marine natural products, we isolated compound 1, which has identical 1D and 2D NMR data to asperspiropene A. Detailed and careful analysis of spectroscopic data led us to revise the structure of asperspiropene A and to determine its absolute configuration.

Polyketides and Meroterpenes from the Marine-Derived Fungi Aspergillus unguis 158SC-067 and A. flocculosus 01NT-1.1.5 and Their Cytotoxic and Antioxidant Activities

“…To the best of our knowledge, the known compounds (2-6) were isolated from A. unguis for the first time. Moreover, we also found that A. flocculosus 01NT-1.1.5 produces various chemical constituents in different culture media [4,13]. This study expanded the chemical and biological diversity of natural products isolated from marine-derived fungi.…”

“…The 1 H NMR spectrum revealed signals of two aromatic protons at δH 6.12 (2H, s, H-4 and H-6); two olefinic protons at δH 5.21 (t, J = 7.0, H-2′) and 5.12 (t, J = 7.0, H-6′); ten methylene protons at δH 3.24 (d, J = 7.1, H2-1′), 2.26 (m, H2-9′), 2.20 (m, H2-8′), 2.07 (dd, J = 7.3, 14.6, H2-5′), and 1.96 (t, J = 7.4, H2-4′); and three methyl groups at δH 2.13 (s, H3-7), 1.74 (s, H3-12′), and 1.57 (s, H3-11′) (Table 1). The 13 C NMR spectrum, in combination with the gHSQC NMR spectrum, displayed nineteen resonances belonging to a carboxyl carbon at δC 177.9 (C-10′); six non-protonated sp 2…”

“…Compound 1 was isolated as a brown solid, and its molecular formula was deduced as , s, H-4 and H-6); two olefinic protons at δ H 5.21 (t, J = 7.0, H-2 ) and 5.12 (t, J = 7.0, H-6 ); ten methylene protons at δ H 3.24 (d, J = 7.1, H 2 -1 ), 2.26 (m, H 2 -9 ), 2.20 (m, H 2 -8 ), 2.07 (dd, J = 7.3, 14.6, H 2 -5 ), and 1.96 (t, J = 7.4, H 2 -4 ); and three methyl groups at δ H 2.13 (s, H 3 -7), 1.74 (s, H 3 -12 ), and 1.57 (s, H 3 -11 ) (Table 1). The 13 C NMR spectrum, in combination with the gHSQC NMR spectrum, displayed nineteen resonances belonging to a carboxyl carbon at δ C 177.9 (C-10 ); six non-protonated sp 2 carbons at δ C 156. The gross structure of 1 was identified by a detailed analysis of 1 H-1 H COSY and HMBC data.…”

“…Compound 7 was isolated as a yellowish powder with a molecular formula of C 13 The structure of a symmetrical 1,4-disubstituted benzene ring was determined by the COSY correlations from H-4 to H-5 and from H-7 to H-8, and the HMBC correlations from H-4 to C-6 and C-8, from H-5 to C-3 and C-7, from H-7 to C-3 and C-5, and from H-8 to C-4 and C-6 (Figure 2). A carboxy methyl group attached to the benzene ring at C-3 was supported by the HMBC correlations from H 2 -2 to C-1, C-3, C-4, and C-8.…”

“…Therefore, the broth extract was selected for further study. The culture broth was extracted with EtOAc, and the organic extract was fractionated into 15 fractions as described previously [13]. Compound 7 (10.0 mg) was purified from fraction 8 by a semipreparative HPLC (YMC-PackODS-A, 250 × 10 mm i.d., 5 µm, flow rate 2.5 mL/min) with an isocratic elution of 25% MeCN in H 2 O for 28.0 min.…”