3.2. Tertiary Amine Catalyzed Asymmetric [4 + 2] Cyclization
General procedure: To a 4 mL vial was sequentially added 3-aroylcoumarines 1 (0.2 mmol), catalyst 4l (0.02 mmol, 10 mol%), and EtOAc (1.0 mL); the mixture was stirred at 0 °C for 15 min before benzyl buta-2,3-dienoate 2b (0.3 mmol, 1.5 equiv.) was charged. The reaction was monitored by TLC analysis. After completion of the reaction, the solvent was removed by rotary evaporation and the residue was directly subjected to column chromatography using PE/EtOAc (20:1–15:1) as the eluent to afford product 3.
Benzyl (E)-2-(5-oxo-4-phenyl-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene) acetate (3a).
White solid (m.p. 121.4–122.1 °C); 1H NMR (400 MHz, CDCl3) δ 7.51–7.31 (m, 12H), 7.20 (t, J = 7.2 Hz, 1H), 7.10 (d, J = 8.0 Hz, 1H), 5.90 (d, J = 1.6 Hz, 1H), 5.23 (s, 2H), 4.87 (dd, J = 14.8, 6.0 Hz, 1H), 4.01 (dd, J = 12.2, 5.6 Hz, 1H), 2.56–2.49 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 166.6, 164.2, 162.3, 161.5, 150.8, 136.0, 133.1, 130.9, 129.2, 129.1, 128.8, 128.5, 128.3, 128.3, 125.8, 124.9, 122.7, 117.3, 102.2, 101.5, 66.4, 30.3, 26.1; [α]D26.0 = + 44.3 (c = 0.26, CHCl3); The enantiomeric purity of 3a was determined by HPLC analysis (DAICEL CHIRALPAK AD–H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 11.2 min (major) and 14.5 min (minor)); HRMS (ESI): Exact mass calcd for C27H21O5 [M+H]+: 425.1389, found: 425.1392.
Benzyl (E)-2-(9-methoxy-5-oxo-4-phenyl-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene) acetate (3b).
White solid (m.p. 131.1–132.8 °C); 1H NMR (400 MHz, CDCl3) δ 7.51–7.36 (m, 10H), 7.03 (d, J = 8.8 Hz, 1H), 6.91 (d, J = 2.0 Hz, 1H), 6.85 (dd, J = 8.8, 2.8 Hz, 1H), 5.91 (d, J = 1.6 Hz, 1H), 5.23 (s, 2H), 4.80 (dd, J = 14.6, 5.6 Hz, 1H), 3.98 (dd, J = 12.0, 5.6 Hz, 1H), 3.83 (s, 3H), 2.58–2.51(m,1H); 13C NMR (101 MHz, CDCl3) δ 166.6, 164.1, 162.1, 161.9, 156.8, 144.7, 136.0, 133.0, 130.8, 129.1, 128.8, 128.5, 128.3, 128.3, 123.7, 118.0, 114.2, 111.1, 102.2, 101.4, 66.4 56.0, 30.5, 25.9; [α]D26.0 = +242.2 (c = 0.49, CHCl3); The enantiomeric purity of 3b was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 15.2 min (major) and 21.0 min (minor)); HRMS (ESI): Exact mass calcd for C28H23O6 [M+H]+: 455.1495, found: 455.1496.
Benzyl (E)-2-(7-methoxy-5-oxo-4-phenyl-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3c).
White solid (m.p. 108.7–110.2 °C); 1H NMR (400 MHz, CDCl3) δ 7.53–7.34 (m, 10H), 7.14 (t, J = 8.4 Hz, 1H), 6.95 (dd, J = 13.0, 8.4 Hz, 2H), 5.91 (d, J = 1.2 Hz, 1H), 5.24 (s, 2H), 4.83 (dd, J = 14.2, 6.0 Hz, 1H), 4.00 (dd, J = 12.4, 6.0 Hz, 1H), 3.90 (s, 3H), 2.57–2.50 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 166.5, 164.2, 162.1, 161.0, 147.8, 140.2, 136.0, 132.9, 130.8, 129.1, 128.7, 128.4, 128.3, 128.2, 124.7, 123.8, 117.0, 111.7, 102.1, 101.2, 66.3, 56.2, 30.5, 26.0; [α]D26.0 = +86.5 (c = 0.5, CHCl3); The enantiomeric purity of 3c was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 13.0 min (major) and 17.0 min (minor)). HRMS (ESI): Exact mass calcd for C28H23O6 [M+H]+: 455.1495, found: 455.1493.
Benzyl (E)-2-(8-methoxy-5-oxo-4-phenyl-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3d).
White solid (m.p. 101.9–102.5 °C); 1H NMR (400 MHz, CDCl3) δ 7.50–7.34 (m, 10H), 7.27–7.24 (m, 1H), 6.74 (dd, J = 8.6, 2.4 Hz, 1H), 6.63 (d, J = 2.4 Hz, 1H), 5.87 (d, J = 1.6 Hz, 1H), 5.21 (s, 2H), 4.81 (dd, J = 14.8, 5.6 Hz, 1H), 3.92 (dd, J = 12.4, 5.6 Hz, 1H), 3.80 (s, 3H), 2.47–2.44 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 166.6, 164.3, 162.2, 161.5, 160.3, 151.5, 136.0, 133.1, 130.8, 129.0, 128.8, 128.4, 128.3, 126.5, 114.5, 111.1, 102.5, 102.0, 101.7, 66.3, 55.7, 29.7, 26.4; [α]D26.0 = −44.3 (c = 0.26, CHCl3); The enantiomeric purity of 3d was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 12.2 min (major) and 17.7 min (minor)). HRMS (ESI): Exact mass calcd for C28H23O6 [M+H]+: 455.1495, found: 455.1498.
Benzyl (E)-2-(9-methyl-5-oxo-4-phenyl-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3e).
White solid (m.p. 127.6–128.9 °C); 1H NMR (400 MHz, CDCl3) δ 7.51–7.35 (m, 10H), 7.18 (s, 1H), 7.12 (d, J = 8.4 Hz, 1H), 6.99 (d, J = 8.0 Hz, 1H), 5.91 (d, J = 1.6 Hz, 1H), 5.24 (s, 2H), 4.87 (dd, J = 14.8, 5.6 Hz, 1H), 3.97 (dd, J = 12.4, 5.6 Hz, 1H), 2.53–2.46 (m, 1H), 2.37 (s,3H); 13CNMR (101 MHz, CDCl3) δ 166.7, 164.4, 162.1, 161.7, 148.7, 136.0, 134.6, 133.1, 130.8, 129.7, 129.0, 128.8, 128.5, 128.3, 128.2, 126.2, 122.2, 117.0, 102.0, 101.6, 66.4, 30.2, 26.1, 21.0; [α]D26.0 = +155.3 (c = 0.50, CHCl3); The enantiomeric purity of 3e was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 12.7 min (major) and 18.5 min (minor)). HRMS (ESI): Exact mass calcd for C28H23O5 [M+H]+: 439.1545, found: 439.1548.
Benzyl (E)-2-(7,9-di-tert-butyl-5-oxo-4-phenyl-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3f).
Yellow solid (m.p. 83.7–84.9 °C); 1H NMR (400 MHz, CDCl3) δ 7.54–7.37 (m, 11H), 7.28 (s, 1H), 5.95 (s, 1H), 5.28 (s, 2H), 4.76 (dd, J = 14.8, 6.0 Hz, 1H), 4.01 (dd, J = 11.6, 6.0 Hz, 1H), 2.77 (t, J = 13.2 Hz, 1H), 1.49 (s, 9H), 1.39 (s, 9H); 13C NMR (101 MHz, CDCl3) δ 166.6, 164.1, 162.1, 161.9, 156.8, 144.7, 136.0, 133.0, 130.9, 129.1, 128.8, 128.5, 128.3, 128.3 123.7, 118.0, 114.2, 111.1, 102.2, 101.4, 66.4, 56.0, 30.5, 25.9; [α]D26.0 = +58.6 (c = 0.52, CHCl3); The enantiomeric purity of 3f was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 6.0 min (major) and 5.1 min (minor)). HRMS (ESI): Exact mass calcd for C35H37O5 [M+H]+: 537.2641, found: 537.2643.
Benzyl (E)-2-(9-fluoro-5-oxo-4-phenyl-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3g).
Yellow solid (m.p. 118.4–119.7 °C); 1H NMR (400 MHz, CDCl3) δ 7.53–7.39 (m, 10H), 7.11–7.00 (m, 3H), 5.93 (d, J = 1.6 Hz, 1H), 5.25 (s, 2H), 4.80 (dd, J = 14.6, 5.6 Hz, 1H), 3.97 (dd, J = 12.4, 5.6 Hz, 1H), 2.56–2.49 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 166.3, 163.5, 162.6, 161.1, 159.4 (d, 1J = 243 Hz), 146.7, 135.9, 132.8, 130.9, 129.0, 128.7, 128.4, 128.2, 128.2, 124.3, 124.2, 118.5, 118.4, 115.8 (d, 2J = 23 Hz), 112.6 (d, 3J = 25 Hz), 102.4, 100.4, 66.4, 30.3, 25.7; [α]D26.0 = −22.8 (c = 0.47, CHCl3); The enantiomeric purity of 3g was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 11.4 min (major) and 14.1 min (minor)). HRMS (ESI): Exact mass calcd for C27H20FO5 [M+H]+: 443.1295, found: 443.1297.
Benzyl (E)-2-(9-chloro-5-oxo-4-phenyl-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3h).
White solid (m.p. 127.4–128.9 °C); 1H NMR (400 MHz, CDCl3) δ 7.50–7.47 (m, 3H), 7.43–7.40 (m, 8H), 7.39–7.28 (m, 1H), 7.03 (d, J = 8.4 Hz, 1H), 5.92 (d, J = 2.0 Hz, 1H), 5.24 (s, 2H), 4.83 (dd, J = 14.6, 5.6 Hz, 1H), 3.98 (dd, J = 12.4, 5.6 Hz, 1H), 2.55–2.47 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 166.4, 163.5, 162.9, 161.0, 149.3, 135.9, 132.8, 131.0, 130.1, 129.2, 129.0, 128.8, 128.5, 128.3, 128.3, 125.9, 124.3, 118.6, 102.6, 100.4, 66.5, 30.3, 25.8; [α]D26.0 = −56.8 (c = 0.19, CHCl3); The enantiomeric purity of 3h was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 13.7 min (major) and 16.4 min (minor)). HRMS (ESI): Exact mass calcd for C27H20ClO5 [M+H]+: 459.0999, found: 459.0997.
Benzyl (E)-2-(9-bromo-5-oxo-4-phenyl-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3i).
White solid (m.p. 131.4–132.7 °C); 1H NMR (400 MHz, CDCl3) δ 7.51–7.35 (m, 12H), 6.98 (d, J = 8.8 Hz, 1H), 5.92 (d, J = 1.2 Hz, 1H), 5.24 (s, 2H), 4.83 (dd, J = 14.6, 6.0 Hz, 1H), 3.99 (dd, J = 12.2, 6.0 Hz, 1H), 2.55–2.48 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 166.4, 163.5, 162.9, 160.9, 149.9, 135.9, 132.8, 132.2, 131.0, 129.0, 128.8, 128.8, 128.5, 128.3, 128.3, 124.8, 119.0, 117.6, 102.6, 100.4, 66.5, 30.3, 25.8; [α]D26.0 = −17.8 (c = 0.22, CHCl3); The enantiomeric purity of 3i was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 17.1 min (major) and 14.2 min (minor)). HRMS (ESI): Exact mass calcd for C27H20BrO5 [M+H]+: 503.0494, found: 503.0490.
Benzyl (E)-2-(8-bromo-5-oxo-4-phenyl-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3j).
White solid (m.p. 119.2–120.7 °C); 1H NMR (400 MHz, CDCl3) δ 7.49–7.46 (m, 3H), 7.45–7.29 (m, 8H),7.24–7.20 (m, 2H), 5.90 (d, J = 2.0 Hz, 1H), 5.21 (s, 2H), 4.80 (dd, J = 14.8, 5.6 Hz, 1H), 3.90 (dd, J = 12.2, 5.6 Hz, 1H), 2.51–2.44 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 166.4, 163.6, 162.8, 160.7, 151.2, 135.9, 132.7, 130.9, 129.0, 128.7, 128.4, 128.3, 127.8, 127.1, 122.0, 121.8, 120.4, 102.4, 100.5, 66.4, 30.0, 25.8; [α]D26.0 = +67.4 (c = 0.52, CHCl3); The enantiomeric purity of 3j was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 14.7 min (major) and 18.0 min (minor)). HRMS (ESI): Exact mass calcd for C27H20BrO5 [M+H]+: 503.0494, found: 503.0497.
Benzyl (E)-2-(5-oxo-4-(p-tolyl)-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3k).
Yellow solid (m.p. 133.2–133.9 °C); 1H NMR (400 MHz, CDCl3) δ 7.44–7.32 (m, 9H), 7.24–7.19 (m, 3H), 7.11 (d, J = 8.0 Hz, 1H), 5.91 (d, J = 1.2 Hz, 1H), 5.24 (s, 2H), 4.87 (dd, J = 14.8, 5.6 Hz, 1H), 3.99 (dd, J = 12.2, 6.0 Hz, 1H), 2.55–2.48 (m, 1H), 2.41 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 166.5, 164.3, 162.4, 161.7, 150.8, 141.3, 136.0, 130.0, 129.1, 129.0, 128.7, 128.4, 128.3, 125.7, 124.8, 122.8, 117.2, 102.0, 100.9, 66.3, 30.3, 26.0, 21.7; [α]D26.0 = +32.2 (c = 0.54, CHCl3); The enantiomeric purity of 3k was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 12.1 min (major) and 18.0 min (minor)). HRMS (ESI): Exact mass calcd for C28H23O5 [M+H]+: 439.1545, found: 439.1543.
Benzyl (E)-2-(5-oxo-4-(m-tolyl)-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3l).
Yellow solid (m.p. 135.6–136.8 °C); 1H NMR (400 MHz, CDCl3) δ 7.43–7.31 (m, 9H), 7.24–7.19 (m, 3H), 7.11 (d, J = 8.4 Hz, 1H), 5.91 (d, J = 1.2 Hz, 1H), 5.24 (s, 2H), 4.87 (dd, J = 14.8, 6.0 Hz, 1H), 3.99 (dd, J = 12.4, 5.6 Hz, 1H). 2.55–2.48 (m, 1H), 2.41 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 166.5, 164.3, 162.4, 161.7, 150.8, 141.3, 136.0, 130.0, 129.1, 129.0, 128.7, 128.4, 128.3, 125.7, 124.8, 122.8, 117.2, 102.0, 100.9, 66.3, 30.3, 26.0, 21.7; [α]D26.0 = +42.2 (c = 0.52, CHCl3); The enantiomeric purity of 3l was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 9.9 min (major) and 13.2 min (minor)). HRMS (ESI): Exact mass calcd for C28H23O5 [M+H]+: 439.1545, found: 439.1544.
Benzyl (E)-2-(4-(4-chlorophenyl)-5-oxo-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3m).
Yellow solid (m.p. 122.5–123.7 °C); 1H NMR (400 MHz, CDCl3) δ 7.46–7.32 (m, 11H), 7.23–7.19 (m, 1H), 7.10 (d, J = 8.0 Hz, 1H), 5.90 (d, J = 1.6 Hz, 1H), 5.23 (s, 2H), 4.86 (dd, J = 14.8, 6.0 Hz, 1H), 4.00 (dd, J = 12.4, 5.6 Hz, 1H), 2.55–2.48 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 166.4, 163.9, 161.4, 161.1, 150.7, 137.0, 136.0, 130.5, 129.3, 128.8, 128.6, 128.5, 128.3, 125.8, 125.0, 122.5, 117.3, 102.3, 101.9, 66.4, 30.3, 26.0; [α]D26.0 = −148.3 (c = 0.49, CHCl3); The enantiomeric purity of 3m was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 13.9 min (major) and 21.5 min (minor)). HRMS (ESI): Exact mass calcd for C27H20ClO5 [M+H]+: 459.0999, found: 459.0999.
Benzyl (E)-2-(4-(3-chlorophenyl)-5-oxo-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3n).
Yellow solid (m.p. 124.5–125.3 °C); 1H NMR (400 MHz, CDCl3) δ 7.49–7.34 (m, 11H), 7.23–7.21 (m, 1H), 7.11–7.09 (m, 1H), 5.92 (d, J = 2.0 Hz, 1H), 5.24 (d, J = 2.0 Hz, 2H), 4.90–4.85 (m, 1H), 4.01–3.98 (m, 1H), 2.52 (t, J = 12.8, 1H); 13C NMR (101 MHz, CDCl3) δ 166.3, 163.8, 161.1, 160.6, 150.6, 135.9, 134.7, 134.2, 131.4, 130.8, 129.5, 129.2, 129.0, 128.7, 128.4, 128.3, 127.4, 125.8, 125.0, 122.3, 117.2, 102.4, 102.2, 66.4, 30.2, 25.9; [α]D26.0 = +100.7 (c = 0.55, CHCl3); The enantiomeric purity of 3n was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 12.4 min (major) and 13.9 min (minor)). HRMS (ESI): Exact mass calcd for C27H20ClO5 [M+H]+: 459.0999, found: 459.1003.
Benzyl (E)-2-(4-([1,1’-biphenyl]-4-yl)-5-oxo-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3o).
White solid (m.p. 130.7–131.4 °C); 1H NMR (400 MHz, CDCl3) δ 7.66–7.60(m, 6H), 7.49–7.33 (m, 10H), 7.22 (t, J = 7.6 Hz, 1H), 7.13 (d, J = 8.0 Hz, 1H), 5.95 (s, 1H), 5.26 (s, 2H), 4.89 (dd, J = 14.8, 5.6 Hz, 1H), 4.03 (dd, J = 12.0, 5.6 Hz, 1H), 2.55 (t, J = 14.0 Hz, 1H); 13C NMR (101 MHz, CDCl3) δ 166.5, 164.2, 162.0, 161.6, 150.8, 143.7, 140.3, 136.0, 129.6, 129.1, 128.9, 128.7, 128.4, 128.3, 127.3, 126.9, 125.8, 117.2, 102.1, 101.4, 66.3, 30.3, 26.0; [α]D26.0 = +91.1 (c = 0,34, CHCl3); The enantiomeric purity of 3o was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 17.9 min (major) and 31.4 min (minor)). HRMS (ESI): Exact mass calcd for C33H25O5 [M+H]+: 501.1702, found: 501.1708.
Benzyl (E)-2-(5-oxo-4-(thiophen-3-yl)-1,10b-dihydro-2H,5H-pyrano[3,4-c]chromen-2-ylidene)acetate (3p).
White solid (m.p. 135.7–136.2 °C); 1H NMR (400 MHz, CDCl3) δ 7.83 (d, J = 3.6 Hz, 1H), 7.53 (d, J = 5.2 Hz, 1H), 7.41–7.30 (m, 7H), 7.18 (t, J = 7.6 Hz, 1H), 7.09 (dd, J = 8.4, 4.8 Hz, 2H), 5.92 (d, J = 1.2 Hz, 1H), 5.27–5.20 (m,2H), 4.70 (dd, J = 15.0, 6.0 Hz, 1H), 4.02 (dd, J = 12.6, 5.6 Hz, 1H), 2.69–2.62 (m,1H); 13C NMR (101 MHz, CDCl3) δ 166.5, 164.0, 163.0, 161.6, 155.2, 150.6, 136.0, 133.6, 132.8, 130.7, 129.1, 128.8, 128.5, 128.3, 127.3, 125.7, 124.9, 122.6, 117.1, 101.8, 100.3, 66.4, 30.9, 29.8, 26.4; [α]D26.0 = +123.7 (c = 0.22, CHCl3); The enantiomeric purity of 3p was determined by HPLC analysis (DAICEL CHIRALPAK AD-H (0.46 cmφ × 25 cm), hexane:2-propanol = 60:40, flow rate = 0.75 mL/min, retention time: 12.4 min (major) and 14.6 min (minor)). HRMS (ESI): Exact mass calcd for C25H19O5S [M+H]+: 459.0999, found: 459.1003.