## 2 Results  
In the chemical investigation of the EtOAc extract, eight compounds, including three benzopyrrole derivatives and five benzopyridine derivatives, were isolated and identified. There are three new compounds (**1-3**, virantomycin D-G) and five known compounds (virantumycin **4**[17], A-503451 D **5**[18], A-503451 D acetylate **6**[18], A-503451 A **7**[18], and A-503451 B **8**[18]) (Figure 1). Compound **1** was obtained as a white amorphous powder. The molecular formula is presented as C\({}_{19}\)H\({}_{27}\)NO\({}_{4}\) by HRESIMS (m/z 356.1838 [M + Na]\({}^{+}\), Figure S7), corresponding to seven degrees of unsaturation. The \({}^{1}\)H NMR spectrum shows three aromatic signals \(\delta\) 7.62 (s), \(\delta\) 7.57 (d, \(J\) = 8.4 Hz), and \(\delta\) 6.50 (d, \(J\) = 8.4 Hz); one methoxyl signal \(\delta\) 3.27 (s); and three methyl signals \(\delta\) 1.19 (s), \(\delta\) 1.03 (s), and \(\delta\) 0.90 (s). The \({}^{13}\)C NMR and DEPT spectra of **1** presents 19 carbon signals, including seven quaternary carbons (one carbonyl and three aromatic signals), four methe carbons (three aromatic signals), four methylene carbons, and four methyl carbons. One carbonyl (\(\delta\) 169.9) and six aromatic (\(\delta\) 148.4, 131.4, 128.8, 119.6, 117.2, and 112.8) signals are displayed in the low field of the \({}^{13}\)C NMR spectrum, indicating the presence of one aromatic system and one carbonyl group for five degrees of unsaturation. Thus, **1** has two other ring structures, besides benzene ring. In the \({}^{1}\)H-\({}^{1}\)H COSY spectrum, the correlations from H-6 to H-2, from H-2 to H-3, from H-8 to H-9, and from H-11 to H-12 are observed (Figure 2). Compound **1** has a benzopyridine skeleton as deduced by the correlations between H-8 and C-4, between H-8 and C-5, between H-8 and C-6, between H-8 and C-10, and between H-9 and C-5 in the HMBC spectrum and the chemical shift value of C-10 (\(\delta\) 54.5) and C-4 (\(\delta\) 143.4) [17]. C-14 is connected to C-9 as determined by the correlations from H-9 to C-14, from H-9 to C-15, from H-9 to C-16, from H-8 to C-14, from H-15 to C-9, and from H-16 to C-9 in the HMBC spectrum. The correlations from H-2 to C-7 and from H-6 to C-7 show that the carbonyl group is located at C-6. The methoxyl group is linked to C-18 as deduced by the correlations between H-19 and C-18 and between H-18 and C-19. The substituent position of the hydroxyl is suggested to be C-13 based on the correlations between H-11  
Figure 1: The structure of compounds **1–8**. and C-13, between H-12 and C-13, between H-15 and C-13, between H-16 and C-13, and between H-17 to C-13. The structure of **1** is determined based on the \({}^{1}\)H-\({}^{1}\)H COSY, HSQC, and HMBC spectra, as shown in Figure 2.  
The coupling constants of H-9 (dd, \(J\) = 14.4, 4.8 Hz) suggest that H-9 is axial. In the ROESY spectrum, the correlations between H-9 and H-8 eq (\(\delta\) 2.64), between H-9 and H-15 (\(\delta\) 1.03), and between H-9 and H-11 ax (\(\delta\) 1.74) are observed (Figure 3). The correlations from H-18 to H-8 ax (\(\delta\) 2.72), from H-18 to H-16 (\(\delta\) 0.90), and from H-18 to H-12 ax (\(\delta\) 1.85) indicate that the orientation of C-18 is axial (Figure 3). The correlations between H-17 and H-12 ax (\(\delta\) 1.85), between H-17 and H-12 eq (\(\delta\) 1.48), between H-17 and H-15 (\(\delta\) 1.03), and between H-17 and H-16 (\(\delta\) 0.90) suggest that the methyl of C-13 is equatorial.