D, J = 7.eight, 3.0, two.1 Hz, 1H, H-10), three.89 (s, 3H, OCH3 ), 3.89 (three.88) (s, 3H, OCH3 ), 3.85 (s, 3H, OCH3 ), three.91-3.82 (overlapped, 1H, H-23), 3.79 (three.78) (s, 3H, OCH3 ), 3.55 (dd, J = 11.7, 3.0 Hz, 1H, H-23), 3.30.09 (m, 4H, two CH2 CH3 ), 1.04 (br.s, 6H, 2 CH2 CH3 ), 0.89 (s, 9H, TBS), 0.06 (s, 6H, TBS). 13 C NMR (75 MHz, CDCl3 ) 186.53, 166.30, 164.20, 162.37, 154.46 (154.40), 149.40, 149.15 (149.09), 144.48, 143.89 (143.85), 129.13 (129.09), 129.03 (128.94), 120.91 (120.78), 120.14 (120.08), 117.04 (116.88), 116.54 (116.36), 111.12 (111.07), 110.43 (110.27), 104.42 (104.38), 93.43, 93.36, 81.25 (81.15), 78.66, 76.09 (76.02), 74.35 (74.27), 62.35, 56.19 (56.17), 56.02 (55.99), 55.94, 55.70 (55.67), 42.15 (41.49), 25.90, 18.37, 13.89 (13.43), -5.07, -5.34. HRMS (ESI): m/z calculated for C39 H52 NO11 Si [MH] : 738.3310. Identified: 738.3329. IR (film) max : 2930, 2854, 1693, 1607, 1573, 1508 cm-1 . HPLC purity 100 (only a single signal was observed for the diastereomers). three.four.three. 23-O-TBS-5,7,20-O-Trimethyl-3-O-(N,N-dimethylthiocarbamoyl)silybin (13) This derivative was achieved by PTLC purification employing EtOAc/hexane (7:three, v/v) followed by hexane/EtOAc (1:1, v/v). Yield, 45 ; Polmacoxib Data Sheet slight yellow strong; 835 C. 1 H NMRMolecules 2021, 26,12 of(300 MHz, CDCl3 ) 7.16 (7.13) (d, J = two.1 Hz, 1H, H-13), 7.09.95 (overlapped, 4H, H-15, H-16, H-18, H-22), 6.89 (d, J = 8.four Hz, 1H, H-21), six.60 (6.57) (d, J = 11.six Hz, 1H, H-3), six.12 (6.11) (d, J = two.three Hz, 1H, H-8), 6.09 (d, J = 2.3 Hz, 1H, H-6), 5.36 (d, J = 11.6 Hz, 1H, H-2), 5.01 (5.00) (d, J = 7.eight Hz, 1H, H-11), 3.98 (ddd, J = 7.8, four.2, 2.7 Hz, 1H, H-10), 3.90 (s, 3H, OCH3 ), three.90 (3.89) (s, 3H, OCH3 ), three.86 (s, 3H, OCH3 ), three.90.82 (overlapped, 1H, H-23), three.80 (s, 3H, OCH3 ), 3.55 (dd, J = 11.7, three.0 Hz, 1H, H-23), three.34 (s, 3H, NCH3 ), 3.ten (s, 3H, NCH3 ), 0.90 (s, 9H, TBS), 0.06 (s, 3H, TBS), 0.06 (0.05) (s, 3H, TBS). 13 C NMR (75 MHz, CDCl3 ) 187.53, 187.49, 166.46, 164.02, 162.40, 149.49, 149.17, 144.74, 143.98, 129.14 (129.09), 128.42 (128.33), 121.05, 120.20, 117.29 (117.17), 116.93 (116.80), 111.18 (111.15), 110.53 (110.38), 104.37, 93.48, 93.46, 81.17, 78.68 (78.64), 77.four, 76.22 (76.16), 62.41, 56.20, 56.06, 56.02, 55.79, 43.37, 38.33, 25.98, 18.44, -5.00, -5.29. HRMS (ESI): m/z calculated for C37 H48 NO10 SSi [MH] : 726.2769. Discovered: 726.2796. IR (film) max : 2929, 2854, 1690, 1607, 1573, 1508 cm-1 . HPLC purity 96.7 (only 1 signal was observed for the diastereomers). 3.5. Synthesis of Tetramethyltaxifolin (14) A reaction flask was charged with taxifolin (20 mg, 0.066 mmol) and potassium carbonate (82 mg, 0.59 mmol), which was vacuumed 3 instances under argon just before the addition of anhydrous acetone (0.47 mL, 0.14 M). Dimethylsulfate (75 , 0.79 mmol) was then added into the reaction flask by means of a long needle. The reaction remedy was refluxed overnight and cooled down to area temperature prior to the aqueous remedy of ammonium chloride (20 mL) was added to quench the reaction. The subsequent 3-Chloro-5-hydroxybenzoic acid Agonist mixture was extracted with ethyl acetate (10 mL three), the combined organic extracts had been dried over anhydrous sodium sulfate, along with the organic solvents have been removed under vacuum. The crude solution was purified over preparative TLC plate eluting with ethyl acetate/hexane (five:1, v/v) and ethyl acetate/hexane (7:three, v/v), sequentially, to furnish the preferred 14 as a slight yellow solid in 86 yield; 14951 C; in [37], 16566 C; in [38], 15355 C. 1 H NMR (300 MHz, CDCl3 ) 7.11 (dd, J = 8.three, 1.9 Hz, 1H, H-6 ), 7.07 (d,.
