*4.2. Fungal Material*

The fungal strain *Mollisia* sp. SCSIO41409 was isolated from a mangrove sediment sample, collected from the Hongsha River estuary near South China Sea, in Sanya city, Hainan Island. The fungus was identified according to the internally transcribed spacer (ITS) region sequence data of the rDNA (supplementary information), and the sequence was deposited in GenBank with the accession number OP872608. A voucher specimen was deposited in the CAS Key Laboratory of Tropical Marine Bioresources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.

#### *4.3. Fermentation and Extraction*

The fungal strain was cultured in 200 mL seed medium (1.5% malt extract, 1.5% sea salt) in 500 mL Erlenmeyer flasks at 28 ◦C for 3 days on a rotary shaker (180 rpm). A large-scale fermentation was incubated statically at 26 ◦C for 60 days using a rice medium (150 g rice, 1.5% sea salt, 150 mL H2O) in the 1 L flask (×53). The whole fermented culture was extracted with EtOAc three times to afford a brown extract (197.2 g).

## *4.4. Isolation and Purification*

The crude extract was chromatographed over a silica gel column eluted with petroleum ether /CH2Cl2 (0–100%, *v*/*v*) and CH2Cl2/CH3OH (0–100%, *v*/*v*) to obtain eleven fractions (Frs. 1–11) based on TLC properties. Fr. 2 was subjected to semipreparative HPLC (63%CH3CN/H2O, 2.5 mL/min) to afford **2** (3.7 mg, tR = 18.6 min) and **1** (9.1 mg, tR = 27.0 min). Fr. 4 was separated by semipreparative HPLC (40% MeCN/H2O, 2.5 mL/min) to afford **9** (7.1 mg, tR = 6.5 min), **8** (4.1 mg, tR = 8.1 min), **3** (27.8 mg, tR = 11.1 min). Fr. 5 was separated by semipreparative HPLC (37% MeCN/H2O, 2.5 mL/min) to afford **6** (8.6 mg, tR = 9.8 min). **4** (8.0 mg, tR = 24.0 min) was obtained from Fr. 6 by semipreparative HPLC eluting with 76% CH3CN/H2O (2.5 mL/min). Fr. 10 was separated by semipreparative HPLC (23% MeCN/H2O, 2.5 mL/min) to afford **7** (22.0 mg, tR = 19.0 min) and **5** (9.0 mg, tR = 12.0 min).

#### *4.5. Spectroscopic Data of Compounds*

8-chlorine-5-hydroxy-2,3-dimethyl-7-methoxychromone (**1**): white needles, m.p. 196–198 ◦C; UV (CH3OH) *λ*max (log *ε*) 327 (3.54), 282 (3.49), 259 (4.10), 244 (4.15), 204 (4.11) nm; IR (film) *ν*max 3734, 2926, 2855, 1717, 1653, 1558, 1437, 1207, 1182, 1103, 820 cm<sup>−</sup>1; 1H and 13C NMR data as shown in Table 1; HRESIMS *m*/*z* 255.0422 [M + H]+ (calcd for C12 H12ClO4 +, 255.0419).

3,4-dichloro-1 *<sup>H</sup>*-pyrrole-2,5-dione (**3**): red needles, m.p. 173–175 ◦C; UV (CH3OH) *λ*max (log *ε*) 235.60 (0.80), 229.20 (0.79) nm; IR (film) *ν*max 3204, 1732, 1609, 1331, 1047, 1026, 851, 735, 673, 550 cm<sup>−</sup>1; 1H NMR (700 MHz, DMSO-*d*6) *δ* 11.71 (s, 1H); 13C NMR (175 MHz, DMSO) *δ* 164.06, 132.82. HRESIMS data at *m*/*z* 163.9318 [M–H]– (calcd for C4Cl2NO2, 163.9312).

## *4.6. X-ray Crystallographic Analysis*

The clear light colorless crystal of **1** was obtained in MeOH by slow evaporation. Crystallographic data for the structure has been deposited in the Cambridge Crystallographic Data Centre. Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB21EZ, UK [fax: +44(0)-1223-336033 or e-mail: deposit@ccdc.cam.ac.uk].

Crystal data for **1**: 2C12H11ClO4, *M*r = 509.31, crystal size 0.3 × 0.03 × 0.02 mm3, triclinic, *a* = 10.3781 (6) Å, *b* = 10.7434 (9) Å, *c* = 11.7251 (8) Å, *α* = 94.077(6)◦, *β* = 101.693 (5)◦, *γ* = 118.572 (7)◦, *V* = 1102.59 (14) Å3, *Z* = 4, *T* = 100.00 (10) K, space group *P*-1, *μ*(Cu K*α*) = 3.099 mm<sup>−</sup>1, *Dcalc* = 1.534 g/cm3, 3879 reflections measured (7.852◦ ≤ 2Θ ≤ 133.17◦), 3879 unique (*R*sigma = 0.0731). The final *R*1 values were 0.0733 (I > 2*σ*(I)). The final *wR*(F2) values were 0.2186 (I > 2*σ*(I)). The final *R*1 values were 0.1004 (all data). The final *wR*(F2) values were 0.2360 (all data). The goodness of fit on F<sup>2</sup> was 1.059 (CCDC 2221470).

Crystal data for **3**: 2C4HCl2NO2, *M*r = 165.96, crystal size 0.09 × 0.06 × 0.06 mm3, monoclinic, *a* = 7.11690 (10) Å, *b* = 8.03280 (10) Å, *c* = 10.2446 (2) Å, *α* = 90◦, *β* = 99.9790(10)◦, *γ* = 90◦, *V* = 576.809 (16) Å3, *Z* = 4, *T* = 100.00 (10) K, space group *P*21/c, *μ*(Cu K*α*) = 9.446 mm<sup>−</sup>1, *Dcalc* = 1.911 g/cm3, 2500 reflections measured (12.63◦ ≤ 2Θ ≤ 148.6◦), 1126 unique (*R*sigma = 0.0272). The final *R*1 values were 0.0239 (I > 2*σ*(I)). The final *wR*(F2) values were 0.0666 (I > 2*σ*(I)). The final *R*1 values were 0.0246 (all data). The final *wR*(F2) values were 0.0671 (all data). The goodness of fit on F<sup>2</sup> was 1.092 (CCDC 2221370).

Crystal data for **4**: 2C30H42O7·CH3OH, *M*r = 1061.31, crystal size 0.06 × 0.06 × 0.05 mm3, orthorhombic, *a* = 6.37690 (10) Å, *b* = 19.5291 (3) Å, *c* = 49.6907 (8) Å, *α* = 94.077(6)◦, *β* = 101.693(5)◦, *γ* = 118.572(7)◦, *V* = 1102.59 (14) Å3, *Z* = 4, *T* = 100.01 (10) K, space group *P*-1, *μ*(Cu K*α*) = 3.099 mm<sup>−</sup>1, *Dcalc* = 1.534 g/cm3, 3879 reflections measured (7.852◦ ≤ 2Θ ≤ 133.17◦), 3879 unique (*R*sigma = 0.0731). The final *R*1 values were 0.0733 (I > 2*σ*(I)). The final *wR*(F2) values were 0.2186 (I > 2*σ*(I)). The final *R*1 values were 0.1004 (all data). The final *wR*(F2) values were 0.2360 (all data). The goodness of fit on F<sup>2</sup> was 1.020. The flack parameter was 0.18 (9) (CCDC 2221376).

## *4.7. Antibacterial Activity Assay*

The antimicrobial activities against six fungi (Botrytis cinerea, Verticillium dahlia kieb., Fusarium graminearum schw., Fusarium oxysporum f.sp. niveum, Rhizoctonia solani, and Septoria nodorum Berk.) and four bacteria (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Streptococcus suis SC19, Erysipelothrix rhusiopathiae WH13013) were evaluated in 96-well plates with a twofold serial dilution method described previously [32]. Cycloheximide and penicillin were used as positive controls against fungi and bacteria, respectively.
