## 4 Experimental Section
### Fermentation, Extraction, and Isolation  
Mutant M6 was selected to perform a large-scale fermentation (33 L) in yeast extract-malt extract broth. The liquid culture was centrifuged at 9000 rpm for 10 min, and the supernatant was extracted at room temperature by ethyl acetate. The residue was extracted at room temperature overnight by a solvent mixture of ethyl acetate:methanol:acetic acid (80:5:5, v:v:v). The second supernatant was then filtered, and the residue was extracted twice more as described above. All the supernatants were combined and concentrated under vacuum at 37 \({}^{\circ}\)C to remove the organic phase. The crude extract (13.4 g) was obtained and was then subjected to silica gel column chromatography with elution by a mixture of dichloromethane (CH\({}_{2}\)Cl\({}_{2}\)) and methanol (MeOH) (gradient from CH\({}_{2}\)Cl\({}_{2}\) (300 mL), 70:1 (v:v, 300 mL), 60:1 (v:v, 300 mL), 50:1 (v:v, 1.5 L), 30:1 (v:v, 800 mL), 10:1 (v:v, 1.5 L), 5:1 (v:v, 1 L), 2:1 (v:v, 1 L), 1:1 (v:v, 600 mL) to MeOH (600 mL)) and ten fractions (Fr.A-Fr.J) were obtained. Guided by HPLC fingerprinting, two fractions, Fr.F (3.09 g) eluted by CH\({}_{2}\)Cl\({}_{2}\):MeOH = 15:1 to 10:1 and Fr.H (1.17 g) eluted by CH\({}_{2}\)Cl\({}_{2}\):MeOH = 2:1, were collected and further subjected to Sephadex LH-20 column chromatography with elution by 100% methanol.  
Fr.F-2 (0.478 g) was a subfraction of Fr.F, which was identified as the target fraction according to the HPLC fingerprints. Fr.F-2 was subsequently subjected to silica gel column chromatography and was eluted with CH\({}_{2}\)Cl\({}_{2}\):MeOH. Fr.F-2-4 (eluted with CH\({}_{2}\)Cl\({}_{2}\):MeOH (40:1, v:v)) showed the target peaks of the xiamenomycin derivatives from UV characterization at \(\lambda_{\rm max}=206\) and 260 nm. Fr.F-2-4 (18 mg) was further purified again by semi-preparative HPLC (Agilent ZOBRAX-C18 column, 5 \(\upmu\)m, 9.4 \(\times\) 250 mm), with the following gradient: CH\({}_{3}\)CN (A)/H\({}_{2}\)O (B): 0 min 42% A, 8 min 42% A, 33 min 72% A, 34 min 100% A, 50 min 100% A, at a flow rate of 1.5 mL/min. One sub-fraction Fr.F-2-4-2 contained compound **2** (1.5 mg). Fr.F-2-2 (8 mg) was subsequently purified by semi-preparative HPLC (Agilent ZOBRAX-C18 column, 5 \(\upmu\)m, 9.4 \(\times\) 250 mm), with the following gradient: CH\({}_{3}\)CN (A)/H\({}_{2}\)O (B): 0 min 45% A, 5 min 45% A, 35 min 100% A, 50 min 100% A, at the flow rate of 1.5 mL/min. One sub fraction Fr.F-2-2-3 was collected as compound **1** (1.5 mg).  
Compound **1**: Yellow amorphous powder (MeOH); \(\left[\alpha\right]^{26}\)\({}_{\rm D}\) +28.45\({}^{\circ}\) (\(c\) 0.0034, MeOH); UV (MeOH) \(\lambda_{\rm max}=206\), 260 nm; CD (\(c\) 0.0024, MeOH) \(\Delta\)\(\varepsilon_{201}\) +12.3, \(\Delta\)\(\varepsilon_{202}\) +9.6, \(\Delta\)\(\varepsilon_{205}\) +8.0, \(\Delta\)\(\varepsilon_{207.4}\) +7.1, \(\Delta\)\(\varepsilon_{213.6}\) +0.14, \(\Delta\)\(\varepsilon_{217}\) -1.2, \(\Delta\)\(\varepsilon_{245.2}\) +2.0, \(\Delta\)\(\varepsilon_{259.8}\) +3.14, \(\Delta\)\(\varepsilon_{283}\) +0.03; \({}^{1}\)H and \({}^{13}\)C NMR data, see Table 2; HRESIMS _m/z_ 290.1768 [M + H]\({}^{+}\), (caled. for C\({}_{17}\)H\({}_{24}\)NO\({}_{3}\), _m/z_ 290.1756), 288.1610 [M - H]\({}^{-}\), (caled. for C\({}_{17}\)H\({}_{22}\)NO\({}_{3}\), _m/z_ 288.2073).  
Compound **2**: Yellow amorphous powder (MeOH); \(\left[\alpha\right]^{30}\)\({}_{\rm D}\) +6.52\({}^{\circ}\) (\(c\) 0.0024, MeOH); UV (MeOH) \(\lambda_{\rm max}\) 206, 260 nm; CD (\(c\) 0.0034, MeOH) \(\Delta\)\(\varepsilon_{205.6}\) +6.7, \(\Delta\)\(\varepsilon_{206.9}\) +5.5, \(\Delta\)\(\varepsilon_{213}\) +20.1, \(\Delta\)\(\varepsilon_{223.4}\) +0.85, \(\Delta\)\(\varepsilon_{260}\) +9.23, \(\Delta\)\(\varepsilon_{296.8}\) +1.0; \({}^{1}\)H and \({}^{13}\)C NMR data, see Table 2; HRESIMS _m/z_ 406.2210 [M + H]\({}^{+}\), (caled. for C\({}_{22}\)H\({}_{32}\)NO\({}_{6}\), _m/z_ 406.2230).