Synthesis of curcusone C derivatives
Derivative C-1. Using 1.5 mL CH2Cl2 dissolved Curcusone C (15.2 mg, 0.048 mmol), and DMF of 2 drops and SO2Cl2 (7.0 µL, 0.096 mmol) were added. Following the reflux reaction by TLC, and the reaction was stopped about 1.5 h later. After drying the solvent, diluting with water, and extracting with ethyl acetate, and the organic layer was washed with saturated salt. Drying with anhydrous Na2SO4, decompression and concentration, derivative C-1 (light yellow solid, 9.3 mg, 57.8%) was purified by PTLC (PE: EtOAc = 5:1).
Derivative C-2. Using 1.5 mL THF dissolved Curcusone C (33.7 mg, 0.108 mmol), tert-butyl hypochlorite (18.3 µL, 0.162 mmol) was added in ice bath. The reaction was gradually raised from 0 °C to room temperature. TLC followed the reaction for about 10 h, and the reaction was stopped and diluted with water. Derivative C-2 (yellow oil, 26.6 mg, 67.6%) was obtained after decompression concentration and purification by PTLC (PE: EtOAc = 4:1).
Derivative C-3. Using 1 mL DMF dissolved Curcusone C (14.8 mg, 0.047 mmol), adding iodine elemental (71.2 mg, 0.281 mmol). The reaction proceeded at room temperature. The reaction was followed by TLC and was stopped after 15 min. After adding sodium thiosulfate solution into the reaction solution, the organic layer was washed with saturated salt. After drying with anhydrous Na2SO4, decompression and concentration, derivative C-3 (light yellow solid, 3.9 mg, 18.0%) was purified by PTLC (PE: EtOAc = 4:1).
Derivative C-13. Curcusone C (25.1 mg, 0.080 mmol) was dissolved in 1 mL THF, and tert-butyl hypochlorite (27.3 µL, 0.240 mmol) was added in ice bath. The reaction was gradually increased from 0 °C to room temperature, followed by TLC, and stopped about 24 h later. After diluting with water, extracting with ethyl acetate for 3 times, using saturated salt washing organic layer, drying with anhydrous Na2SO4, and condensing under pressure by PTLC (PE: EtOAc = 4: 1), derivative C-13 (yellow oily, 27.9 mg, 87.0%) was purified.
Derivative C-4. Using 1.5 mL DMSO dissolved derivative C-13. Then, KH2PO4 and catalytic KI (5% equiv) were added, and heated to 80 °C for about 20 h. Quenched with water after the reaction was complete, and extracted with ethyl acetate for 3 times. Then, combining with organic layer, washing with saturated salt, and drying by anhydrous Na2SO4. Derivative C-4 (28.0 mg, 52.2%, after two steps) was purified by PTLC (CH2Cl2: MeOH = 60:1) after decompression concentration.
Derivative C-5. Derivative C-13 (14.2 mg, 0.036 mmol) was dissolved in 1 mL acetone, followed by the addition of potassium acetate (14.2 mg, 0.140 mmol) and catalytic amount of KI (5% equiv). The reaction was carried out at room temperature, followed by TLC tracking reaction. After about 48 h, the reaction was complete and stopped. The combined organic layer was dried with anhydrous Na2SO4. After decompression concentration, derivative C-5 (yellow solid, 8.4 mg, 55.9%) was purified by PTLC (PE: EtOAc = 2:1).
Derivative C-6. Derivative C-13 was dissolved in 1.5 mL acetone followed by reflux reaction with potassium sorbate (58.2 mg, 0.376 mmol) and a catalytic amount of KI (5% equiv). TLC tracked reaction, and the reaction was complete about 30 h later. The reaction was stopped, and the acetone was dried under pressure, diluted with water, and ethyl acetate extraction for 3 times. The combined organic layer was dried with anhydrous Na2SO4, condensed under pressure and purified by PTLC (CH2Cl2: MeOH = 80:1) to obtain derivative C-6 (6.9 mg, 15.1% after two steps).
Derivative C-7. Derivative C-13 (20.7 mg, 0.052 mmol) was dissolved in 1 mL acetone, followed by the addition of KI (13.2 mg, 0.080 mmol), and the reaction was stopped at room temperature for 20 h. The acetone was dried under pressure, dichloromethane was dissolved, the insoluble matter was filtered out, and the crude product was obtained by drying. The crude product was dissolved in 1.6 mL DMSO: H2O = 3:5. Then, cuprous oxide (14.2 mg, 0.099 mmol) was added to the solvent, heated to 50 °C. The reaction was stopped for about 8 h, the insoluble matter was filtered out, diluted with water, extracted with ethyl acetate for 3 times, and the combined organic layer was dried with anhydrous Na2SO4. After decompression, the concentration was processed by PTLC (PE: EtOAc = 2: 1). Derivative C-7 (yellow solid, 7.1 mg, 36.0%) was purified.
Derivative C-8. Derivative C-13 (14.2 mg, 0.036 mmol) was dissolved in 1 mL acetone, followed by the addition of potassium acetate (14.2 mg, 0.140 mmol) and catalytic amount of KI (5% equiv). The reaction was carried out at room temperature, followed by TLC tracking reaction. After about 48 h, the reaction was complete and stopped. The combined organic layer was dried with anhydrous Na2SO4. After decompression and concentration, derivative C-8 (yellow solid, 8.4 mg, 55.9%) was purified by PTLC (PE: EtOAc = 2:1).
Derivative C-9. Derivative C-13 (20.2 mg, 0.051 mmol) was dissolved in 1.5 mL acetone, followed by the addition of mono-methyl malonate potassium salt (33.0 mg, 0.211 mmol) and catalytic amount of KI (5% equiV). The reflux reaction was followed by TLC tracking reaction. After about 48 h, the reaction was complete. The combined organic layer was dried with anhydrous Na2SO4 and purified by PTLC (PE: EtOAc = 2:1) after decompression and concentration, derivative C-9 (yellow oily, 13.6 mg, 56.5%) was obtained.
Derivative C-10. Derivative C-2 (14.5 mg, 0.040 mmol) was dissolved in 1 mL DMF, followed by potassium acetate (6.0 mg, 0.061 mmol), reacted at room temperature. The reaction was followed by TLC, and stopped for about 12 h. Then, the reaction was diluted with water, extracted with ethyl acetate for 3 times, and washed with saturated salt for the combined organic layer. Derivative C-10 (yellow oily, 6.3 mg, 40.8%) was purified by PTLC (PE: EtOAc = 3:1) after anhydrous Na2SO4 drying and decompression concentration.
Derivative C-11. Derivative C-2 (16.8 mg, 0.046 mmol) was dissolved in 1 mL DMF, diethylamine (9.5 µL, 0.092 mmol) and K2CO3 (19.9 mg, 0.144 mmol) were added to react at room temperature, followed by TLC, and the reaction was stopped for about 12 h, diluted with water. Derivative C-11 (yellow oily, 5.6 mg, 30.4%) was obtained after decompression concentration and purification by PTLC (PE: EtOAc = 3:1).
Derivative C-12. Derivative C-13 (26.0 mg, 0.0651 mmol) was dissolved in 1.5 mL acetone, followed by the addition of sodium p-nitrophenol (32.1 mg, 0.163 mmol) and catalytic amount of KI (5% equiV). The reaction was performed at room temperature, followed by TLC follow-up reaction, and the reaction was complete and stopped about 24 h later. The combined organic layer was dried with anhydrous Na2SO4. After decompression and concentration, derivative C-12 was purified by PTLC (CH2Cl2: MeOH = 70:1) to obtain a brown-yellow solid, 11.1 mg, 28.3%.
Derivative C-14. Derivative C-13 (28.9 mg, 0.072 mmol) was dissolved in 1.5 mL acetone, followed by the addition of potassium indolebutyrate (37.2 mg, 0.144 mmol) and catalytic amount of KI (5% equiv). The reflux reaction was followed by TLC tracking reaction. After about 48 h, the reaction was complete and stopped. The combined organic layer was dried with anhydrous Na2SO4. After decompression and concentration, derivative C-14 was purified by PTLC (PE: EtOAc = 2:1) to obtain an oily brown-yellow color, 10.1 mg, 24.6%.
Derivative C-15. Curcusone C (19.2 mg, 0.062 mmol), hydroxylamine hydrochloride (7.2 mg, 0.104 mmol) and potassium acetate (12.1 mg, 0.123 mmol) were dissolved in 1.5 mL methanol. The reflux reaction was followed by TLC, and the reaction was stopped after about 4 h. The organic layer was washed with saturated salt, dried with anhydrous Na2SO4, concentrated under reduced pressure, and purified by PTLC (PE: EtOAc = 2:1) to obtain derivative C-15 (yellow solid, 14.3 mg, 67.4%).
Positive probe. Hexylic acid (16.5 µL, 0.150 mmol) was dissolved in 1.5 mL CH2Cl2, and SO2Cl2 (163 µL, 2.250 mmol) was added for reflux reaction. The reaction was stopped about 8 h later. The CH2Cl2 and SO2Cl2 were removed under pressure to obtain the crude product of hexylic chloride. Added 1 mL CH2Cl2 to dissolve, drop by drop into the sample solution of CH2Cl2 with Cur C (15.2 mg, 0.048 mmol), Et3N (20.3 µL, 0.146 mmol) and DMAP (catalytic volume, 5%). The reflux reaction was stopped after about 12 h. The organic layer was dried with anhydrous Na2SO4. After decompression, PTLC (PE: EtOAc = 5:1) was concentrated to obtain positive probe (yellow oily, 12.7 mg, 64.2%).
Negative probe. The positive probe (22.1 mg, 0.054 mmol) was dissolved in 1.5 mL methanol, followed by the addition of hydroxylamine hydrochloride (5.8 mg, 0.083 mmol) and potassium acetate (9.0 mg, 0.091 mmol). The reflux reaction was followed by TLC, and stopped about 4 h later. Methanol was distilled under pressure, diluted with water, extracted with ethyl acetate. Then, the organic layer was washed with water and dried with anhydrous Na2SO4. PTLC (PE: EtOAc = 3:1) was concentrated under pressure to obtain negative probe (yellow solid, 10.5 mg, 43.9%).
The instrument used in this part are AVANCE III-400 NMR instrument (Bruck, Switzerland), AVANCE III-500 NMR instrument (Bruck, Switzerland) and QSTAR Plusar I mass spectrometer (Thermo, USA).