## 4 Materials and Methods
### Extraction and Isolation  
The ethyl acetate extract (55.0 g) was performed on a silica gel column using a gradient mixture of petroleum ether-ethyl acetate (15:1-0:1) as the eluent to produce 13 major fractions. Fr.7 was separated by Sephadex LH-20 using methanol to further purify, and 3 fractions (Fr.7.1-Fr.7.3) were obtained by combining the same parts according to HPLC behavior. Fr.7.2 was separated by a preparative HPLC using CH3 CN (30-90%) as an eluent (24 mL/min) to afford compounds **4** (52.3 mg, tR = 22.19 min), **6** (3.8 mg, tR = 21.61 min), and **7** (3.5 mg, tR = 23.14 min). Fr.8 was chromatographed on a silica gel column, eluted with petroleum ether-ethyl acetate (4:1-0:1), and yielded 3 fractions (Fr.8.1-8.3). Fr.8.2 and Fr.8.3 were combined and then further separated over preparative HPLC to obtain **1** (6.3 mg, tR = 11.00 min) and **8** (5.7 mg, tR = 13.42 min). Fr.9 was subjected to a silica gel column using petroleum ether-ethyl acetate (4:1-0:1) to provide four portions (Fr.9.1-Fr.9.4). Among them, Fr.9.2 was subjected to a Sephadex LH-20 (MeOH) to provide 4 portions. Fr.9.2.3 was eluted on a preparative HPLC column (7.5 mL/min) with 70% CH3 CN to give compound **5** (19.3 mg, tR = 13.93 min). Fr.10 was subjected to a preparative HPLC using 24% CH3 CN to obtain compound **3** (8.6 mg, tR = 10.06 min). Finally, Fr.11 was chromatographed on a silica gel column and then purified by a preparative HPLC (elute with CH3 CN-H2O, gradient from 20:80 to 80:20; 24.0 mL/min) to give compound **2** (9.0 mg, tR = 12.53 min).  
Virantumycin D (**1**): white amorphous powder; [\(\alpha\)]\({}^{25}_{\mathrm{D}}\) -15.0\({}^{\circ}\) (\(c\) 0.001, MeOH); UV (MeOH) \(\lambda_{\mathrm{max}}\) (log \(\epsilon\)): 230 (4.02), 310 (4.41) nm; CD (\(c\) 0.90 mM, MeOH) \(\lambda_{\mathrm{max}}\)(\(\Delta\epsilon\)) 207 nm (\(-3.55\)), 233 nm (\(-\)0.91), 285 nm (\(+\)2.03), 318 nm (\(-\)0.80); \({}^{1}\)H NMR (600 MHz, CD\({}_{3}\)OD) and \({}^{13}\)C NMR (150 MHz, CD\({}_{3}\)OD) data, see Table 1; HR-ESI-MS _m_/\(\dot{\simeq}\) 356.1838 [M + Na]\({}^{+}\) (calcd for C\({}_{19}\)H\({}_{27}\)NO\({}_{4}\)Na, 356.1826).  
Virantumycin E (**2**): white amorphous powder; [\(\alpha\)]\({}^{25}_{\mathrm{D}}\) -127.9\({}^{\circ}\) (\(c\) 0.001, MeOH); UV (MeOH) \(\lambda_{\mathrm{max}}\) (log \(\epsilon\)): 236 (3.98), 317 (4.44) nm; CD (\(c\) 0.86 mM, MeOH) \(\lambda_{\mathrm{max}}\)(\(\Delta\epsilon\)) 213 nm (\(-\)2.09), 316 nm (\(-\)4.94); \({}^{1}\)H NMR (600 MHz, CD\({}_{3}\)OD) and \({}^{13}\)C NMR (150 MHz, CD\({}_{3}\)OD) data, see Table 1; HR-ESI-MS _m_/\(\dot{\simeq}\) 372.1787 [M + Na]\({}^{+}\) (calcd for C\({}_{19}\)H\({}_{27}\)NO\({}_{5}\)Na, 372.1787).  
Virantumycin F (**3**): white amorphous powder; [\(\alpha\)]\({}^{25}_{\mathrm{D}}\) -11.2\({}^{\circ}\) (\(c\) 0.001, MeOH); UV (MeOH) \(\lambda_{\mathrm{max}}\) (log \(\epsilon\)): 230 (4.02), 318 (4.42) nm; CD (\(c\) 0.82 mM, MeOH) \(\lambda_{\mathrm{max}}\)(\(\Delta\epsilon\)) 210 nm (\(-\)1.60), 225 nm (\(-\)0.49), 249 nm (\(+\)0.26), 288 nm (\(-\)1.10), 315 nm (\(+\)0.37); \({}^{1}\)H NMR (600 MHz, CD\({}_{3}\)OD) and \({}^{13}\)C NMR (150 MHz, CD\({}_{3}\)OD) data, see Table 1; HR-ESI-MS _m_/\(\dot{\simeq}\) 390.1441 [M + Na]\({}^{+}\) (calcd for C\({}_{19}\)H\({}_{26}\)CINO\({}_{4}\)Na, 390.1448).