*3.2. Extraction and Isolation*

With assistance from the Aquatic Resources Research Institute, Chulalongkorn University and approval from the Department of Fisheries, Ministry of Agriculture and Cooperatives, Thailand (0510.2/8234, Date: 28 October 2019), a Thai blue sponge (*Xestospongia* sp.) was collected during a SCUBA diving mission at a depth of 3–5 m at Sichang Island, the Gulf of Thailand. The fresh blue sponge was mashed and subsequently pre-treated with 10% potassium cyanide solution in a phosphate-buffered solution at pH 7. Next, the suspension was macerated with methanol. The extraction process was repeated three times. The methanolic extracts were filtered, combined, and concentrated at reduced pressure. The condensed aqueous-methanolic extract was partitioned with hexane and ethyl acetate. The ethyl acetate extract was further concentrated and purified by silica gel column chromatography using hexane and ethyl acetate as the eluent. Natural renieramycins, including renieramycin M (**4**), renieramycin N (**5**) [11], and renieramycin O (**6**) [12], were obtained. Thereafter, compound **4** was transformed into Jorunnamycin A (**3**) under a three-step semisynthesis including hydrogenation, hydride reduction, and air oxidation [21,24].

### *3.3. Screening of the Photoredox Reaction Conditions with the Renieramycins*

Natural renieramycins **4**–**6** were employed as the starting material for the light-induced intramolecular photoredox reaction. A solution of the renieramycin alkaloid (15 mg) with 20 mL of the selected solvent (CH2Cl2, CHCl3, and THF) was stirred vigorously under a light source comprising white light (18 W fluorescent) and blue light (4 W LED) for 24 h at room temperature under a nitrogen atmosphere. The reaction was monitored by TLC using a solution of ethyl acetate and hexane (1:1 *v*/*v*) as the mobile phase. After the completion of the reaction, the solvent was evaporated under reduced pressure. The resultant crude product was purified by flash column chromatography using silica gel as the stationary phase and the mixed solvents of ethyl acetate and hexane as the mobile phase to afford the corresponding products, **7** and **8**.
