All required chemicals, solvents, and reagents were purchased from Sigma-Aldrich or Merck and were of reagent grade. All synthesized compounds were purified by column chromatography (silica gel 60; gradient elution with ethyl acetate (EtOAc)/petroleum ether (PE) /dichloromethane (DCM)). Merck Silica Gel 60 F254 plates were used for analytical TLC. Melting points were estimated using a Gehaka PF 1000 melting point apparatus. Compounds were fully characterized by 1H NMR, 13C NMR and 19F NMR if appropriate, using either a Bruker Avance 300 or 400 spectrometer. Splitting patterns are described as singlet (s), doublet (d), doublet of doublets (dd), triplet (t), quartet (q) and multiplet (m). Chemical shifts are expressed as δ (ppm) and coupling constants (J) in Hertz (Hz). Mass spectral analyses were recorded using a LCT Premiere XE (ESI-TOF MS) instrument or a Bruker micrOTOF-QIII instrument. All calculated exact mono isotopic mass distributions were calibrated against internal reference standards. IR data was obtained with a Thermo scientific microlet I s10 instrument model 1510 or a Shimadzu IR Prestige-21 spectrophotometer.

Synthesis and characterization of series 1 compounds

4-acetylphenyl acetate (10)

The compound was prepared and characterized as previously described in the literature [31]. Yield: 98%.

1,1-(4-hydroxy-1,3-phenylene)diethanone (11)

The compound was prepared and characterized as previously described in the literature [32]. Yield: 17%.

6-acetyl-2,2-dimethylchroman-4-one (12)

Compound 11 (2.5 g, 14.2 mmol), acetone (2.3 mL), and morpholine (0.7 mL) were added to the ionic liquid [bbim]Br (2 g) and stirred at 95–100 °C for 8 hours [22]. The reaction mixture was extracted with ethyl acetate (3 × 30 mL) and the organic layers dried over anhydrous sodium sulfate and concentrated under reduced pressure. The crude residue was purified by column chromatography (Petroleum ether (PE): ethyl acetate (EtOAc)). Characterization agreed with previously reported values [33]. Yield: 67%.

6-(1-hydroxyethyl)-2,2-dimethylchroman-4-one (1)

Compound 12 (200 mg, 0.9 mmol), dissolved in dimethylformamide (1.5 mL) was added to water (500 mL) containing D. carota slices (150 g). The reaction mixture was stirred vigorously for 7 days at room temperature. The reaction was then extracted with ethyl acetate (6 × 50 mL), and the organic layers dried over anhydrous sodium sulfate and concentrated under reduced pressure. The crude residue was purified by column chromatography (PE: EtOAc). Yellow oil, yield: 29%, αD (20 °C) −18.3 (c = 0.95, CH2Cl2); IR: 3393, 1724, 1679, 1616, 1488, 1372, 1252, 1203, 1128, 930, 835 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.37 (6H, s, (CH3)2), 1.41 (3H, d, J = 6.53 Hz, CH3CH), 2.63 (2H, s, CH2CO), 4.79 (1H, q, J = 6.53 Hz, CH3CH), 6.85 (1H, d, J = 8.53 Hz, Ar-H), 7.47 (dd, J = 8.53, 2.26 Hz, Ar-H), 7.74 (1H, d, J = 2.26 Hz, Ar-H); 13C NMR (100 MHz, CDCl3) δ = 24.9 (CH3), 26.6 (2CH3), 48.8 (CH2), 69.6 (COH), 79.3 (C2), 118.6 (Ar-CH), 119.6 (Ar-C), 123.3 (Ar-CH), 133.8 (Ar-C), 138.1 (Ar-CH), 159.4 (Ar-C), 192.8 (CO). Characterization agreed with previously reported values [13].

1-(2,2-dimethyl-4-oxochroman-6-yl)ethyl but-2-enoate (13a)

Compound 1 (20 mg, 0.09 mmol), but-2-enoic acid (15 mg, 0.18 mmol), 4-dimethylaminopyridine (5 mg, 0.045 mmol) and N,N′-dicyclohexylcarbodiimide (37 mg, 18 mmol) were dissolved in dichloromethane (5 mL) and stirred at room temperature for 20 h. The reaction mixture was filtered, washed with 1 M NaOH and extracted with dichloromethane (3 ×20 mL). The organic layers were dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by column chromatography (PE: EtOAc). Colourless oil, yield: 15%. IR: 1716, 1690, 1618, 1489, 1436, 1372, 1255, 1176, 1062, 967, 833 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.45 (6H, s, (CH3)2), 1.54 (3H, d, J = 6.6 Hz, CH3), 1.87 (3H, dd, J = 6.9, 1.4 Hz, CH3C=C), 2.71 (2H, s, CH2), 5.84-5.91 (2H, m, CH and CH=C), 6.90 (1H, d, J = 8.6 Hz, Ar-H8), 6.99 (1H, m, CH=C), 7.48 (1H, dd, J = 8.6, 2.2 Hz, Ar-H7), 7.87 (1H, d, J = 2.1 Hz, Ar-H5); 13C NMR (100 MHz, CDCl3) δ = 18.0 (CH3), 22.0 (CH3), 26.6 (CH3), 26.7 (CH3), 48.8 (CH2), 71.2, 79.3, 118.5 (Ar-CH), 119.9 (Ar-C), 122.8 (CH), 124.0 (Ar-CH), 134.4 (Ar-C), 134.5 (Ar-CH), 145.0 (CH), 159.5 (Ar-C), 165.8 (COO), 192.5 (CO). HRMS (M + Na)+ 311.1257, C17H20O4Na requires 311.1259.

1-(2,2-dimethyl-4-oxochroman-6-yl)ethyl 3-methylbut-2-enoate (13b)

50 mg (0.22 mmol) of 1 was reacted as for 13a with trans-3-methylbut-2-enoic acid (27 mg, 0.45 mmol) to afford 13b. Colourless oil, yield: 11%. IR: 1695, 1653, 1619, 1263, 705 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.38 (6H, s, (CH3)2, 1.48 (3H, d, J = 6.8 Hz, CH3CH), 1.73 and 1.76 (6H, (CH3)2C=C), 2.64 (2H, s, CH2CO), 5.81 (2H, m, CH and CH=C), 6.83 (1H, d, J = 8.5 Hz, Ar-H), 7.41 (1H, dd, J = 8.5, 2.3 Hz, Ar-H), 7.79 (1H, d, J = 2.3 Hz, Ar-H); 13C NMR (100 MHz, CDCl3) δ = 20.3 (CH3), 26.7 (CH3)2), 27.5 (CH3), 48.8 (CH2), 64.6 (CH2), 79.4 (C2), 115.7 (C=CH), 118.7 (C = CH), 119.9 (quat. C), 126.4 (C=CH), 128.9 (quat. C), 136.3 (C=CH), 157.6 (quat. C), 159.8 (quat. C), 166.3 (COO), 192.3 (CO).

1-(2,2-dimethyl-4-oxochroman-6-yl)ethyl cinnamate (13c)

50 mg (0.22 mmol) of 1 was reacted as for 13a with cinnamic acid (67 mg, 0.45 mmol) to afford 13c. Colourless oil, yield: 61%. IR: 1710, 1692, 1618, 1490, 1255, 1168 cm−1. 1H NMR (400 MHz, CDCl3): δ = 1.46 (6H, d, J = 2.2 Hz, CH3CCH3), 1.60 (3H, d, J = 6.6 Hz, CH3CH), 2.72 (2H, s, CH2), 5.98 (1H, q, J = 6.4 Hz, CHCH3), 6.46 (1H, d, J = 15.9 Hz, CH=CH), 6.92 (1H, d, J = 8.6 Hz, ArH), 7.38 (3H, m, 3 x ArH), 7.52 (3H, m, 3 x ArH) 7.69 (1H, d, J = 16.1 Hz, CH=CH), 7.92 (1H, d, J = 2.2 Hz, ArH); 13C NMR (100 MHz, CDCl3) δ = 22.0, 26.6, 26.7, 48.8, 71.7, 79.0, 118.3, 118.6, 124.1, 128.1 (2C), 128.9 (2C), 130.3, 134.2, 134.4, 134.5, 145.0, 158.5, 166.2, 192.4 (one quat. C obscured). HRMS (M+Na)+ 373.1411, C22H22O4Na requires 373.1416.

1-(2,2-dimethyl-4-oxochroman-6-yl)ethyl (E)-4-phenylbut-3-enoate (13d)

60 mg (0.3 mmol) of 1 was reacted as for 13a with 4-phenylbut-3-enoic acid (50 mg, 0.6 mmol) to afford 13d. Colourless oil, yield: 64%. IR: 1734, 1700, 1616, 1257, 750 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.45 (6H, d, J = 3.2 Hz, CH3CCH3), 1.54 (3H, d, J = 6.6 Hz, CH3CH), 2.71 (2H, s, CH2), 3.26 (2H, d, J = 7 Hz, CH2C = C), 5.87 (1H, q, J = 6.5 Hz, CHCH3), 6.30 (1H, dt, J = 7 Hz, CH2CH=CH), 6.48 (1H, d, J = 16 Hz, CH2CH=CH), 6.90 (1H, d, J = 8.6 Hz, H8), 7.20–7.36 (6H, m, 5 x ArH), 7.47 (1H, dd, J = 8.6, 2.1 Hz, H7), 7.87 (1H, d, J = 2.1 Hz, H5); 13C NMR (100 MHz, CDCl3) δ = 21.9, 26.6, 26.7, 38.6, 48.8, 72.0, 79.4, 118.6, 119.9, 121.6, 124.1, 126.3 (2C), 127.6, 128.5 (2C), 133.5, 134.0, 134.5, 136.8, 159.6, 170.9, 192.4. HRMS (M+Na)+ 387.1563, C23H24O4Na requires 387.1567.

Synthesis and characterization of series 2 compounds

1-(2,2-dimethylchroman-6-yl)ethanone (14)

Compound 9 (2.50 g, 18.4 mmol) was dissolved in formic acid (75 mL) and 2-methylbut-3-en-2-ol (1.58 g, 18.3 mmol) was added slowly. The mixture was heated to reflux for 8 h. It was then cooled, ice cold H2O (200 mL) was added and the mixture was extracted with CH2Cl2 (3 × 100 mL). The combined organic layers were washed with saturated NaHCO3 and then dried (Na2SO4), concentrated in vacuo and the residue purified by flash chromatography (PE: EtOAc). Colourless oil, yield: 20%. Characterization agreed with previously reported values [34].

1-(2,2-dimethylchroman-6-yl)ethanol (15)

To compound 14 (1 g, 4.9 mmol) dissolved in methanol (15 mL) was slowly added sodium borohydride (0.25 g, 6.6 mmol). The mixture was stirred at room temperature for 2 hours, and then extracted with dichloromethane (3 × 30 mL). The organic layers were dried over anhydrous sodium sulfate concentrated under reduced pressure and purified by column chromatography (PE: EtOAc). Yellow oil, yield: 100%. IR: 3354, 1616, 1587, 1495, 1367, 1252, 1121, 1070, 820, 607 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.25 (6H, s, (CH3)2), 1.39 (3H, d, J = 6.27 Hz, CH3), 1.72 (2H, t, CH2), 2.69 (2H, t, CH2), 4.72 (1H, q, CH), 6.69 (1H, d, J = 8 Hz, Ar-H), 7.01 (2H, m, 2 x Ar-H); 9.03 (OH); 13C NMR (100 MHz, CDCl3) δ = 22.6 (CH2), 24.9 (CH3), 26.9 (CH3), 26.9 (CH3), 32.8 (CH2), 70.1 (CHOH), 74.3 (C2), 117.2 (Ar-CH), 120.8 (Ar-C), 124.6 (Ar-CH), 126.6 (Ar-C), 136.9 (Ar-CH), 153.4 (Ar-C).

1-(2,2-dimethylchroman-6-yl)ethyl but-2-enoate (16a)

Compound 15 (100 mg, 0.5 mmol) and but-2-enoic acid (80 mg, 1 mmol), 4-dimethylaminopyridine (3 mg, 0.025 mmol) and N,N′-dicyclohexylcarbodiimide (200 mg, 1 mmol)) was dissolved in DCM (5 mL) and stirred at room temperature for 20 h. The reaction mixture was filtered, washed with 1 M NaOH and extracted with DCM. The organic layer was dried over anhydrous sodium sulfate, concentrated under reduced pressure and purified by column chromatography (PE: EtOAc). Yellow oil, yield: 37%. IR: 1713, 1497, 1151, 1122, 1099, 1059, 967, 820 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.24 (6H, s, (CH3)2), 1.46 (3H, d, J = 6.53 Hz, CH3CH), 1.71 (2H t, J = 6.78 Hz, CH2), 1.79 (3H, dd, J = 6.9, 1.6 Hz, CH3C=C), 2.68 (2H, t, J = 6.78 Hz, CH2), 5.80 (2H, m, CH=CH and CH3CH), 6.68 (d, J = 8.28 Hz, Ar-H), 6.89 (1H, m, CH = CH), 6.99 (br. s, Ar-H), 7.03 (1H, dd, J = 8.53, 2.26 Hz, Ar-H); 13C NMR (100 MHz, CDCl3) δ = 18.0 (CH3), 22.0 (CH2), 22.5 (CH3), 26.9 (2CH3), 32.7 (CH2), 71.9 (CH), 74.3 (C), 117.2 (Ar-CH), 120.6 (CH), 123.1 (Ar-C), 125.3 (Ar-CH), 127.7 (Ar-CH), 132.7 (C), 144.5 (CH), 153.7 (Ar-C), 165.9 (CO). HRMS (M + Na)+ 297.1462, C17H22O3Na requires 297.1467.

1-(2,2-dimethylchroman-6-yl)ethyl 2-methylbut-2-enoate (16b)

Compound 15 (200 mg, 1 mmol) was reacted as for 16a with trans-2-methyl-but-2-enoic acid (100 mg, 2 mmol) to afford 16b. Yellow oil, yield: 7%. IR: 1714, 1497, 1224, 1142, 1059, 947, 819 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.25 (6H, s, (CH3)2), 1.46 (3H, d, J = 6.53 Hz, CH3), 1.70–1.80 (8H, m, 2 x CH3 and CH2), 2.69 (2H, t, CH2), 5.80 (1H, q, CH), 6.68 (1H, d, J = 8.53 Hz, Ar-H), 6.81 (1H, m, CH=CH), 6.98–7.04 (2H, m, 2x CH=CH); 13C NMR (100 MHz, CDCl3) δ = 12.1 (CH3), 14.3 (CH3), 22.2 (CH3), 22.5 (CH2), 26.9 (2CH3), 32.8 (CH2), 72.0 (CH), 74.3 (C2), 117.2 (CH=CH), 120.6 (quat. C), 125.2 (CH=CH), 127.5 (CH=CH), 129.0 (quat. C), 133.1 (quat. C), 136.9 (CH=CH), 153.6 (Ar-C), 167.4 (CO). HRMS (M+) 288.1723, C18H24O3 requires 288.1725.

1-(2,2-dimethylchroman-6-yl)ethyl 3-methylbut-2-enoate (16c)

Compound 15 (200 mg, 1 mmol) was reacted as for 16a with trans-3-methyl-but-2-enoic acid (100 mg, 2 mmol) to afford 16c. Yellow oil, yield: 7%. IR: 1705, 1527, 1304, 1121, 1059, 819, 733 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.24 (6H, s, (CH3)2), 1.44 (3H, d, J = 6.53 Hz, CH3CH), 1.71 (2H, t, CH2), 1.79 (3H, s, CH3), 2.08 (3H, s, CH3), 2.68 (2H, t, CH2), 5.62 (1H, d, J = 1.00 Hz, CH), 5.77 (1H, q, CH3CH), 6.67 (1H, d, J = 8.28 Hz, Ar-H), 6.99 (1H, s, Ar-H), 7.01 (dd, Ar-H); 13C NMR (100 MHz, CDCl3) δ = 19.2 (CH3). 21.1 (CH3), 21.5 (CH2), 25.9 (CH3), 26.3 (2CH3), 31.7 (CH2) 70.1 (CH), 73.2 (C2), 115.5 (CH), 116.2 (CH), 119.6 (Ar-C), 124.3 (Ar-CH), 126.5, (CH), 132.0 (Ar-C), 152.6 (quat. C), 155.4 (quat. C), 164.9 (CO). HRMS (M + Na)+ 311.1614, C18H24O3Na requires 311.1618.

1-(2,2-dimethylchroman-6-yl)ethyl 4-phenylbut-3-enoate (16d)

Compound 15 (200 mg, 1 mmol) was reacted as for 16a with 4-phenylbut-3-enoic acid (32 mg, 2 mmol) to afford 16d. Yellow oil, yield: 17%. IR: 1728, 1496, 1294, 1209, 1121, 1057, 819, 691 cm−1. 1H NMR (CDCl3, 400 MHz) δ = 1.24 (6H, s, C(CH3)2), 1.46 (3H, d, J = 6.53 Hz, CH3CH), 1.70 (2H, t, J = 6.78 Hz, CH2), 2.67 (2H, td, J = 6.65 Hz, CH2), 3.17 (2H, d, J = 6.3 Hz, CH2C=C), 5.78 (1H, q, J = 6.53 Hz, CH3CH), 6.23 (1H, m, CH2CH=CH), 6.39 (1H, d, J = 19 Hz, CH2CH=CH), 6.67 (1H, d, J = 8.3 Hz, H8), 6.99 (1H, br. s, H5), 7.01 (1H, dd, J = 8.3, 2.3 Hz, H7), 7.12–7.29 (5H, m, ArCH2´-6´); 13C NMR (100 MHz, CDCl3) δ = 20.9, 21.4, 25.9, 31.7, 37.7, 71.6, 73.3, 116.2, 119.6, 120.9, 124.3, 125.2 (2 x ArCH), 126.4, 126.7, 127.5 (2 x ArCH), 131.3, 132.3, 135.9, 152.8, 169.9. HRMS (M + Na)+ 373.1774, C23H26O3Na requires 373.1780.

1-(2,2-dimethylchroman-6-yl)ethyl 4,4,4-trifluoro-3-methylbut-2-enoate (16e)

Compound 15 (100 mg, 0.5 mmol) was reacted as for 16a with 4,4,4-trifluoro-3-methylbut-2-enoic acid (150 mg, 1 mmol) to afford 16e. Colourless oil, yield: 24%. IR: 1722, 1498, 1293, 1197, 1122, 1096, 1059, 947, 892 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.25 (6H, s, C(CH3)2), 1.49 (3H, d, J = 6.53 Hz, CH3CH), 1.72 (3H, t, CH2), 2.15 (3H, d, J = 1.51 Hz, CH3C=C), 2.69 (2H, t, CH2), 5.83 (1H, q, CH3CH) 6.25 (1H, d, CH = C), 6.69 (d, J = 8.28 Hz, Ar-H), 7.01 (2H, m, 2Ar-H); 13C NMR (100 MHz, CDCl3) δ = 11.3 (CH3), 20.8 (CH3), 21.5 (CH2), 25.9 (2CH3), 31.7 (CH2), 72.1 (CH), 73.4 (C2), 116.3 (CH=C), 119.8 (Ar-CH), 120.9 (Ar-C), 124.4 (Ar-CH), 126.7 (Ar-CH), 130.9 (Ar-C), 140.6 (quat. C), 153.0 (quat. C), 163.2 (CO); 19F NMR (376.5 MHz, CDCl3): δ = −71.3 (CF3). HRMS (M+) 342.1435, C18H21O3F3 requires 342.1443.

N-(1-(2,2-dimethylchroman-6-yl)ethyl)acetamide (16f)

Compound 15 (50 mg, 0.25 mmol), acetamide (16 mg, 0.25 mmol), and FeCl3 (20 mg, 0.12 mg) were dissolved in nitromethane (3 mL) and stirred overnight at room temperature, after which time the reaction was concentrated under reduced pressure and purified by column chromatography (PE: EtOAc). Colourless oil, yield: 34%. IR: 3282, 1738, 1644, 1494, 1456, 1367, 1257, 1121, 946, 818 cm−1. 1H NMR (400 MHz, CDCl3): δ = 1.25 (6H, s, (CH3)2), 1.39 (3H, d, J = 6.78 Hz, CH3CH), 1.71 (2H, t, CH2), 1.89 (3H, s, CH3CO), 2.68 (2H, t, CH2), 4.96 (1H, m, CH3CH), 5.60 (1H, br. s, NH), 6.67 (d, J = 8.3 Hz, Ar-H), 6.94 (2H, m, 2Ar-H); 13C NMR (100 MHz, CDCl3): δ = 21.5 (CH3), 22.5 (CH2), 25.9 (CH3), 28.7 (2CH3), 31.7 (CH2), 47.3 (CH) 73.3 (C2), 116.4 (Ar-CH), 119.9 (Ar-C), 124.0 (Ar-CH), 126.6 (Ar-CH), 133.1 (Ar-C), 152.3 (Ar-C), 168.0 (CO). HRMS (M + Na)+ 270.1469, C15H21NO2Na requires 270.1465.

N-(1-(2,2-dimethylchroman-6-yl)ethyl)acrylamide (16g)

Compound 15 (120 mg, 0.58 mg) was reacted as for 16f with acrylamide (40 mg, 0.58) to afford 16g. Colourless oil, yield: 53%. IR: 3269, 1653, 1624, 1494, 1233, 1208, 1121, 946, 728 cm−1. 1H NMR (400 MHz, CDCl3): δ = 1.24 (6H, s, (CH3)2), 1.41 (3H, d, J = 6.78 Hz, CH3CH); 1.70 (2H, t, CH2), 2.66 (2H, t, CH2), 5.05 (1H, m, CH3CH), 5.52 (1H, dd, H of CH2), 6.01 (2H, H of CH2 and NH), 6.19 (1H, C=CH), 6.65 (1H, d, J = 8.28 Hz, Ar-H), 6.95 (2H, m, 2Ar-H); 13C NMR (100 MHz, CDCl3): δ = 21.6 (CH3), 22.5 (CH2), 26.9 (2CH3) 32.7 (CH2), 48.3 (CH), 74.2 (C2), 117.3 (Ar-CH), 120.8 (Ar-C), 125.1 (Ar-CH), 126.3 (CH2), 127.7 (Ar-CH), 131.1 (CH), 134.1 (Ar-C), 153.3 (Ar-C), 164.6 (CO). HRMS (M + Na)+ 282.1477, C16H21NO2Na requires 282.1465.

Synthesis and characterization of series 3 compounds

1-(4-(3-hydroxypropoxy)phenyl)ethanone (17)

4-hydroxyacetophenone (10 g, 73.44 mmol), 3-chloro-1-propanol (7.3 mL), K2CO3 (13 g, 94 mmol), and KI (120 mg, 0.7 mmol) were dissolved in DMF (100 mL), and stirred at 100 °C for 18 h, after which time water was added, and the reaction extracted with diethyl ether (3 × 100 mL). The organic layers were washed sequentially with 1 M NaOH and saturated NaCl solution, dried over anhydrous sodium sulfate, concentrated under reduced pressure and purified by column chromatography (PE: EtOAc). Characterization agreed with previously reported values [35].

3-(4-acetylphenoxy)propanoic acid (18)

Compound 17 (3.3 g, 17 mmol) and KMnO4 (13.7 g, 86.8 mmol) were dissolved in acetone (150 mL) and stirred at room temperature for 18 h. Sodium thiosulfate saturated solution was added, followed by acidification with 1 M HCl. The mixture was then extracted with DCM (3 × 100 mL), washed with saturated NaCl solution, dried over anhydrous sodium sulfate and concentrated under reduced pressure. White solid, yield: 100%; mp 142 °C; IR (KBr) 3489, 2921, 2349, 2306, 1727, 1660, 1559, 1421, 1362, 1268, 1173, 1034, 960, 833, 671 cm−1. 1H NMR (270 MHz, CDCl3): δ = 2.56 (3H, s, CH3), 2.89 (2H, t, CH2), 4.32 (2H, t, CH2), 6.95 (2H, d, 2Ar-H), 7.94 (2H, d, 2Ar-H); 13C NMR (67.5 MHz, CDCl3): δ = 26.5 (CH3), 34.1 (CH2), 63.4 (CH2), 114.4 (2Ar-CH), 130.8 (2Ar-CH), 162.4 (Ar-C), 175.1 (COOH), 197.1 (CO).

6-acetylchroman-4-one (19)

Compound 18 (1 g, 4.8 mmol) and PPA (20 g) were stirred at 100 °C for 5 h, after which time was added water, and the reaction stirred for 5 minutes. It was extracted with DCM, washed with saturated NaCl solution dried over anhydrous sodium sulfate, concentrated under reduced pressure and purified by column chromatography (DCM: EtOAc). White solid, yield: 44%; mp 115 °C; IR (KBr): 2998, 2919, 1686, 1604, 1491, 1424, 1357, 1247, 1129, 1027, 837, 754 cm−1. 1H NMR (270 MHz, CDCl3): δ = 2.60 (3H, s, CH3). 2.87 (2H, t, CH2), 4.62 (2H, t, CH2), 7.04 (1H, d, Ar-H), 8.14 (1H, dd, Ar-H), 8.48 (1H, d, Ar-H); 13C NMR (67.5 MHz, CDCl3): δ = 26.4 (CH3), 37.4 (CH2), 67.3 (CH2), 118.7 (Ar-CH), 120.4 (Ar-C), 128.7 (Ar-CH), 130.9 (Ar-C), 135.3 (Ar-CH), 165.2 (Ar-C), 190.9 (CO), 196.3 (CO).

6-(1-hydroxyethyl)chroman-4-one (20)

Compound 19 (100 mg, 0.53 mmol) dissolved in DMF (1.5 mL) was added to water (500 mL) and D. carota slices (40 g). The reaction mixture was vigorously stirred at room temperature for 3 days. The reaction was then extracted with ethyl acetate (6 × 100 mL), dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by column chromatography (DCM: EtOAc). Yellow oil, yield: 79%; αD (20 °C) −3.62 (c = 1.28, CH2Cl2); IR (KBr): 3517, 2232, 1708, 1681, 1607, 1498, 1357, 1250, 1135, 1050, 831, 733 cm−1. 1H NMR (270 MHz, CDCl3): δ = 2.10 (2H, m, CH2). 2.57 (3H, s, CH3), 4.37 (2H, m, CH2), 4.88 (1H, s, CH), 6.90 (1H, d, Ar-H), 7.82 (1H, d, Ar-H), 8.01 (1H, d, Ar-H); 13C NMR (67.5 MHz, CDCl3): δ = 26.3, 30.5, 37.4, 62.6, 63.1, 117.2 (Ar-CH), 124.2 (Ar-C), 130.1 (Ar-C), 130.3 (Ar-CH), 130.8 (Ar-CH), 158.9 (Ar-C), 190.9 (CO), 196.8 (CO). HRMS (M + Na)+ 215.0677, C11H12O3Na requires 215.0679.

6-acetylchroman-4-yl (E)-but-2-enoate (21a)

Compound 20 (100 mg, 0.5 mmol), but-2-enoic acid (90 mg, 1 mmol), 4-dimethylaminopyridine (31 mg, 0.25 mmol) and N,N′-dicyclohexylcarbodiimide (214 mg, 1 mmol) were dissolved in DCM (5 mL) and stirred at room temperature for 20 h. The reaction mixture was filtered, washed with 1 M NaOH, and extracted with DCM. The organic layer was dried over anhydrous sodium sulfate, concentrated under reduced pressure, and purified by column chromatography (PE: EtOAc) to afford 21a. Colourless oil, yield: 7%; IR: 1712, 1675, 1247, 1169, 1049, 833 cm−1. 1H NMR (400 MHz, CDCl3): δ = 1.89 (3H, dd, J = 7.0, 1.6 Hz, CH = CHCH3), 2.13–2.30 (2H, m, CHCH2), 2.54 (3H, s, COCH3), 4.29–4.41 (2H, m, OCH2), 5.87 (1H, dd, J = 15.4, 1.7 Hz, CH=CH), 6.01 (1H, t, J = 3.7 Hz, CH), 6.91 (1H, d, J = 8.6 Hz, Ar-H8), 7.03 (1H, m, CH=CH), 7.87 (1H, dd, J = 8.8, 2.2 Hz, Ar-H7), 7.94 (1H, d, J = 2.2 Hz, Ar-H5); 13C NMR (100 MHz, CDCl3): δ = 18.0, 26.3, 28.1, 62.7, 64.6, 117.4, 120.1, 122.5, 130.2, 130.5, 132.1, 145.8, 159.4, 165.7, 196.6. HRMS (M + Na)+ 283.0948, C15H16O4Na requires 283.0941.

6-acetylchroman-4-yl (Z)-2-methylbut-2-enoate (21b)

Compound 20 (80 mg, 0.40 mmol) was reacted as for 21a with trans-2-methyl-but-2-enoic acid (83 mg, 0.8 mmol) to afford 21b. Colourless oil, yield: 17%; IR (KBr): 3050, 2921, 1671, 1605, 1494, 1435, 1250, 1134, 1057, 975, 828, 739 cm−1. 1H NMR (400 MHz, CDCl3): δ = 1.79 and 1.85 (6H, m, 2 x CH3). 2.17 (2H, m, CH2), 2.54 (3H, s, CH3), 4.37 (2H, m, CH2), 6.03 (1H, m, CH), 6.90 (2H, m, CH and Ar-H), 7.87 (1H, d, Ar-H), 7.95 (1H, d, Ar-H); 13C NMR (100 MHz, CDCl3): δ = 12.1, 14.4, 26.3, 28.1, 62.8, 64.7, 117.3 (Ar-CH), 120.2 (Ar-C), 128.5 (Ar-C), 130.2 (Ar-C), 130.5 (Ar-CH), 132.1 (Ar-CH), 138.2 (Ar-CH), 159.4 (Ar-C), 167.3 (CO), 196.7 (CO). HRMS (M + Na)+ 297.1099, C16H18O4Na requires 297.1097.

6-acetylchroman-4-yl 3-methylbut-2-enoate (21c)

Compound 20 (80 mg, 0.40 mmol) was reacted as for 21a with trans-3-methyl-but-2-enoic acid (83 mg, 0.8 mmol) to afford 21c. Colourless oil, yield: 20%. IR: 3055, 2925, 2223, 1713, 1677, 1607, 1501, 1358, 1253, 1140, 1076, 1018, 832, 735, 703 cm−1. 1H NMR (400 MHz, CDCl3): δ = 1.90 (3H, d, CH3). 2.11–2.29 (2H, m, CH2), 2.21 (3H, s, CH3), 2.54 (3H, s, COCH3), 4.26–4.20 (2H, m, OCH2), 5.69 (1H, t, CH), 5.98 (1H, 5, J = 3.5 Hz, CH), 6.90 (1H, d, J = 8.8 Hz, Ar-H8), 7.86 (1H, dd, J = 8.6, 2.2 Hz, Ar-H7), 7.95 (1H, d, J = 2.2 Hz, Ar-H5); 13C NMR (100 MHz, CDCl3): δ = 20.4, 26.3, 27.5, 28.1, 62.8, 63.8, 115.8, 117.3, 120.4, 130.2, 130.4, 132.0, 158.2, 159.4, 165.8, 196.7. HRMS (M + Na)+ 297.1102, C16H18O4Na requires 297.1097.

1-(4-oxochroman-6-yl)ethyl 4-phenylbut-3-enoate (21d)

Compound 20 (60 mg, 0.3 mmol), was reacted as for 21a with 4-phenylbut-3-enoic acid (50 mg, 0.6 mmol) to afford 21d. Colourless oil, yield: 34%; IR: 1729, 1672, 1606, 1358, 1248, 1139, 1046 cm−1. 1H NMR (400 MHz, CDCl3): δ = 2.13–2.29 (2H, m, CH2), 2.52 (3H, s, CH3), 3.30 (2H, d, J = 7.1 Hz, CH2), 4.28–4.41 (2H, m, CH2), 5.99 (1H, t, J = 3.5 Hz, CH), 6.30 (1H, dt, J = 15.9, 7.1 Hz, CH=CH), 6.51 (1H, d, J = 15.9 Hz, CH = CH), 6.91 (1H, d, J = 8.8 Hz, Ar-H8), 7.22–7.37 (5H, m, 5 x Ar-H),), 7.88 (1H, dd, J = 8.7, 1.8 Hz, Ar-H7), 7.94 (1H, d, J ~ 2 Hz, Ar-H5); 13C NMR (100Mz, CDCl3): δ = 26.3 (CH3), 27.9 (CH2), 38.6 (CH2C=C), 62.6 (OCH2), 65.3 (OCH), 117.4 (CH), 120.0 (ArC), 121.2 (CH), 126.3 (2CH), 127.7 (CH), 128.6 (2CH), 130.2 (ArC), 130.6 (CH), 132.1 (CH), 133.9 (CH), 136.7 (ArC), 159.3 (ArC), 171.0 (OC = O), 196.6 (C=O). HRMS (M + Na)+ 359.1253, C21H20O4Na requires 359.1254.

Synthesis and characterization of series 4 compounds

(E)-N-((2,2-dimethyl-4-oxochroman-6-yl)methyl)but-2-enamide (24a)

To a solution of trans-2-butenoic acid (0.084 g, 0.98 mmol) in dichloromethane (15 mL) at 0oC under a N2 atmosphere was added EDC (0.28 g, 1.48 mmol) and triethylamine (0.18 mL, 1.30 mmol). After 30 minutes, 23 (200 mg, 0.98 mmol) was added to this solution. The reaction was allowed to reach room temperature and stirred for 24 hours. The residual solvent was removed in vacuo, the residue extracted with saturated bicarbonate/DCM, and the crude organic residue purified by flash column chromatography to afford amide (24a). Colourless oil, yield: 28%; IR (neat): 3267, 1690, 1615, 1574, 1485, 1191, 973, 924, 834 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.37 (6H, s, C(CH3)2), 1.78 (3H, dd, J = 6.9, 1.0 Hz, CH3CH=CH), 2.63 (2H, s, CH2C = O), 4.37 (2H, d, J = 6 Hz, NHCH2), 5.75 (1H, dd, J = 15.2, 1.6 Hz, CH=CH), 5.85 (1H, br., NH), 6.77–6.86 (2H, m, H8 and CH=CHCH3), 7.37 (1H, dd, J = 8.5, 2.3 Hz, H7), 7.65 (1H, d, J = 2.1 Hz, H5); 13CNMR (100Mz, CDCl3) δ = 17.8 (CH3C=C), 26.6 ((CH3)2), 42.6 (NHCH2), 48.8 (CH2C = O), 79.3 (C2), 118.9 (CH), 119.8 (ArC), 124.7 (CH), 125.2 (CH), 130.9 (ArC), 136.1 (CH), 140.6 (CH), 159.4 (ArC), 165.9 (NHC=O), 192.5 (C4). HRMS (M + Na)+ 296.1269, C16H19NO3Na requires 296.1263.

(E)-N-((2,2-dimethyl-4-oxochroman-6-yl)methyl)-2-methylbut-2-enamide (24b)

100 mg (0.49 mmol) of 23 was reacted as for 24a with trans-2,3-dimethylacrylic acid (49 mg, 0.49 mmol) to afford 24b. Colourless oil, yield: 61%; IR (neat): 3305, 1689, 1616, 1530, 1352, 1296, 1254, 1188, 1129, 683 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.37 (6H, s, C(CH3)2), 1.67 (3H, d, J = 6.8 Hz, CH3CH = C), 1.77 (3H, br. s, CH3C=CH), 2.62 (2H, s, CH2C=O), 4.35 (2H, d, J = 5.8 Hz, NHCH2), 6.18 (1H, br., NH), 6.40 (1H, q, J = 6.8 Hz, CH3CH=C), 6.81 (1H, d, J = 8.5 Hz, H8), 7.37 (1H, dd, J = 8.5, 2.5 Hz, H7), 7.65 (1H, dd, J = 2, 0.5 Hz, H5); 13CNMR (100Mz, CDCl3) δ = 12.4 (CH3C=C), 14.0 (CH3C = C), 26.6 ((CH3)2), 42.9 (NHCH2), 48.7 (CH2C=O), 79.3 (C2), 118.9 (CH), 119.8 (ArC), 125.2 (CH), 131.1 (ArC), 131.3 (CH), 131.4 (ArC), 136.1 (CH), 159.3 (ArC), 169.3 (NHC = O), 192.5 (C4). HRMS (M-H)+ 288.1446, C17H20NO3 requires 288.1443.

N-((2,2-dimethyl-4-oxochroman-6-yl)methyl)-3-(thiophen-2-yl)acrylamide (24c: E/Z mix)

200 mg (0.98 mmol) of 23 was reacted as for 24a with 3-(2-thienyl)acrylic acid (0.15 g, 0.97 mmol) to afford amide 24c. Off-white solid, yield: 60%; IR (neat): 3271, 1693, 1649, 1612, 1555, 1487, 1231, 1208, 828 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.37 (6H, s, C(CH3)2), 2.63 (2H, s, CH2C = O), 4.43 (2H, d, J = 5.9 Hz, NHCH2), 6.02 (1H, br., NH), 6.16 (1H, d, J = 15.3 Hz, CH=CH), 6.83 (1H, d, J = 8.6 Hz, H8), 6.95 (1H, m, CH), 7.13 (1H, d, J = 3.3 Hz, CH), 7.23 (1H, d, J = 5 Hz, CH), 7.40 (1H, dd, J = 8.6, 2.1 Hz, H7), 7.70 (2H, m, CH and H5); 13CNMR (100Mz, CDCl3) δ = 26.6 ((CH3)2), 42.9 (NHCH2), 48.8 (CH2C=O), 79.4 (C2), 119.0 (CH), 119.2 (CH), 119.9 (ArC), 125.3 (CH), 127.4 (CH), 128.0 (CH), 130.5 (CH), 130.7 (CH), 136.2 (CH), 134.3 (CH), 139.9 (ArC), 159.4 (ArC), 165.6 (NHC=O), 192.5 (C4). HRMS (M + H)+ 342.1149, C19H20NO3S requires 342.1164.

N-((2,2-dimethyl-4-oxochroman-6-yl)methyl)cinnamamide (24d)

100 mg (0.49 mmol) of 23 was reacted as for 24a with trans-cinnamic acid (72 mg, 0.49 mmol) to afford amide 24d. White solid, yield: 21%; IR (neat): 3258, 2924, 1691, 1655, 1617, 1552, 1486, 1385, 1221 cm−1. 1H NMR (CDCl3, 400 MHz) δ = 1.44 (6H, s, C(CH3)2), 2.69 (2H, s, CH2C=O), 4.51 (2H, d, J = 5.9 Hz, NHCH2), 6.18 (1H, br., NH), 6.43 (1H, d, J = 15.7 Hz, COCH=CH), 6.90 (1H, d, J = 8.6 Hz, H8), 7.33–7.37 (3H, m, 3 x ArH), 7.46–7.50 (3H, m, 3 x ArH), 7.66 (1H, d, J = 15.7 Hz, CH=CHAr), 7.77 (1H, d, J = 2.2 Hz, H5); 13C NMR δ = 26.6 ((CH3)2), 42.9 (NHCH2), 48.8 (CH2C=O), 79.4 (C2), 119.0 (CH), 119.9 (ArC), 120.3 (CH), 125.3 (CH), 127.8 (2xCH), 128.8 (2xCH), 129.8(CH), 130.8 (ArC), 134.7 (ArC), 136.2 (CH), 141.6 (CH), 159.4 (ArC), 165.9 (NHC=O), 192.5 (C4). HRMS (M-H)+ 334.1434, C21H20NO3 requires 334.1443.

(E)-N-((2,2-dimethyl-4-oxochroman-6-yl)methyl)-4-phenylbut-3-enamide (24e)

100 mg (0.49 mmol) of 23 was reacted as for 24a with 4-phenylbut-3-enoic acid (79 mg, 0.49 mmol) to afford amide 24e. Colourless oil, yield: 36%; IR (neat): 3286, 1644, 1487, 1300, 1257, 1189, 966, 693 cm−1. 1H NMR (400 MHz, CDCl3) δ = 1.37 (6H, s, C(CH3)2), 2.63 (2H, s, CH2C=O), 3.14 (2H, dd, J = 7.3, 1.5 Hz, CH2C=C), 4.33 (2H, d, J = 5.8 Hz, NHCH2), 5.90 (1H, br., NH), 6.24 (1H, m, CH2CH=CH), 6.47 (1H, d, J = 16 Hz, CH2CH = CH), 6.82 (1H, d, J = 8.5 Hz, H8), 7.16–7.32 (5H, m, ArCH2´-6´), 7.35 (1H, dd, J = 8.5, 2.3 Hz, H7), 7.65 (1H, d, J = 2.3 Hz, H5); 13CNMR (100Mz, CDCl3) δ = 26.6 ((CH3)2), 40.8 CH2C = C), 42.9 (NHCH2), 48.8 (CH2C = O), 79.4 (C2), 119.0 (C8), 119.9 (ArC), 122.1 (ArCH), 125.3 (C5), 126.4 (2 x ArCH), 127.9 (ArC), 128.6 (2 x ArCH), 130.6 (ArC), 135.0 (ArCH), 136.0 (C7), 136.5 (ArC), 159.4 (ArC), 170.6 (NHC=O), 192.4 (C4). HRMS (M-H)+ 348.1612, C22H22NO3 requires 348.1600.

General procedure for the synthesis of phosphonium salts (26)

A mixture of ω-bromocarboxylic acid (1 equiv.) and triphenylphosphine (1 equiv.) in 20 mL of toluene was refluxed for 24–48 h under nitrogen. The mixture was allowed to cool at room temperature and concentrated in vacuo. The residue was crystallized from various solvents to give the corresponding phosphonium salt in yields between 46–96%.

General procedure for the synthesis of unsaturated carboxylic acids (28)

To a stirred suspension of phosphonium salt 26 (1 equiv) in dry THF (10 mL) was slowly added lithium bis(trimethylsilyl)amide (1.0 M in THF). The solution was stirred for 30 min, and then cooled to −78 °C. A solution of benzaldehyde 27 (1 equiv.) was then added dropwise. The reaction was allowed to warm to room temperature overnight. Water and ether were added. The water layer was separated and acidified with 1 M aqueous hydrochloric acid to pH 1, then extracted twice with ethyl acetate. The combined organic layers were dried over sodium sulfate, filtered and concentrated in vacuo. The crude product was chromatographed on silica gel (hexane:ethyl acetate) to afford the acid products as oils.

5-phenylpent-4-enoic acid (28f) ~2:1 mix of E/Z.

Commercial (3-carboxypropyl)triphenylphosphonium bromide (1 g, 2.33 mmol) was reacted using the general procedure to obtain 28f. Colourless waxy semi-solid, yield: 75%. 1H NMR (CDCl3, 400 MHz) δ = 2.49–2.71 (4H, m, (CH2)2), 5.64 & 6.22 (1H, 2 x m, C=CH), 6.45 & 6. 49 (1H, 2 x d, C=CH), 7.19–7.38 (5H, m, 5 x ArH); 13C NMR δ = 27.9, 33.8, 126.1, 127.2, 128.0, 128.5, 128.7, 130.1, 131.2, 137.2, 179.1 (signals of dominant E isomer).

6-phenylhex-5-enoic acid (28g) (2.5:1 mix of E/Z)

Commercial (4-carboxybutyl)triphenylphosphonium bromide (1 g, 2.26 mmol) was reacted using the general procedure to obtain 28g. Colourless oil, yield: 74%. 1H NMR (CDCl3, 400 MHz) δ = 1.83 (2H, m, (CH2), 2.25–2.43 (4H, m, (CH2)2), 5.63 & 6.18 (1H, 2 x dt, C=CH), 6.41 & 6.47 (1H, 2 x d, C = CH), 7.18–7.35 (5H, m, 5 x ArH); 13C NMR δ = 24.2, 32.3, 33.4, 126.0, 127.1, 128.2, 128.5, 128.7, 129.3, 131.0, 137.5, 180.1 (signals of dominant E isomer).

7-phenylhept-6-enoic acid (28h) 1.3:1 mix of E/Z.

26h (1.0 g, 2.19 mmol) was reacted using the general procedure to obtain 28h. Colourless oil, yield: 58%. 1H NMR (CDCl3, 400 MHz) δ = 1.53 (2H, m, (CH2), 1.70 (2H, m, (CH2), 2.22–2.43 (4H, m, (CH2)2), 5.64 & 6.21 (1H, 2 x dt, C=CH), 6.39 & 6.43 (1H, 2 x d, C = CH), 7.17–7.35 (5H, m, 5 x ArH); 13C NMR δ = 24.2 & 24.3, 28.2 & 28.7, 29.3 & 32.6, 33.9 & 33.9, 125.9, 126.5, 126.9, 128.1, 128.5, 128.5, 128.7, 129.3, 130.2, 130.2, 130.2, 130.2, 132.2, 133.8, 137.6 & 137.7, 172.0 & 179.9.

8-phenyloct-7-enoic acid (28i) 1:1.7 mix of E/Z.

26i (1.7 g, 3.61 mmol) was reacted using the general procedure to obtain 28i. Orange-brown oil, yield: 7%. 1H NMR (CDCl3, 400 MHz) δ = 1.33–1.53 (4H, m, (CH2)2), 1.64 (2H, m, (CH2), 2.17–2.38 (4H, m, (CH2)2), 5.64 & 6.21 (1H, 2 x dt, C=CH), 6.38 & 6.41 (1H, 2 x d, C=CH), 7.17–7.35 (5H, m, 5 x ArH); 13C NMR δ = 24.6, 28.4, 28.8, 29.6, 32.8, 125.9, 126.5, 128.2, 128.5, 128.8, 129.0, 132.8, 137.7, 179.8 (signals of dominant Z isomer).

(E)-N-((2,2-dimethyl-4-oxochroman-6-yl)methyl)-5-phenylpent-4-enamide (24f)

100 mg (0.49 mmol) of 23 was reacted as for 24a with 28f (86 mg, 0.49 mmol) to afford amide 24f. Colourless oil, yield: 48%; IR (neat): 3297, 2925, 1689, 1637, 1618, 1488, 1372, 1253, 1208, 1191, 964 cm−1. 1H NMR (CDCl3, 400 MHz) δ = 1.44 (6H, s, C(CH3)2), 2.38 (2H, br. t, CH2), 2.58 (2H, m, CH2), 2.69 (2H, s, CH2C=O), 4.39 (2H, d, J = 5.9 Hz, NHCH2), 5.84 (1H, br., NH), 6.20 (1H, 2 x t, J = 6.9 Hz, CH2CH=CH), 6.43 (1H, d, J = 16 Hz, CH2CH=CH), 6.82 (1H, d, J = 8.6 Hz, H8), 7.18–7.33 (5H, m, ArCH2´-6´), 7.39 (1H, dd, J = 8.5, 2.4 Hz, H7), 7.72 (1H, d, J = 2.4 Hz, H5); 13C NMR δ = 26.6 ((CH3)2), 29.0 (CH2), 36.4 (CH2), 42.7 (NHCH2), 48.8 (CH2C=O), 79.4 (C2), 119.0 (CH), 119.8 (ArC), 125.3 (CH), 126.1 (2 x CH), 127.2 (CH), 128.5 (2 x CH), 128.6 (CH), 130.8 (ArC), 131.2 (CH), 136.1 (CH), 137.3 (ArC), 159.4 (ArC), 172.1 (NHC=O), 192.5 (C4). HRMS (M-H)+ 362.1772, C23H24NO3 requires 362.1756.

N-((2,2-dimethyl-4-oxochroman-6-yl)methyl)-6-phenylhex-5-enamide, 3:1 E/Z (24g)

110 mg (0.54 mmol) of 23 was reacted as for 24a with 28g (102 mg, 0.54 mmol) to afford amide 24g. Semi-solid gum, yield: 30%; IR (neat): 3292, 2929, 1687, 1644, 1617, 1487, 1256, 1188 cm−1. 1H NMR (CDCl3, 400 MHz) δ = 1.44 (6H, s, C(CH3)2), 1.85 (2H, m, CH2), 2.18–2.41 (4H, m, (CH2)2), 2.70 (2H, s, CH2C=O), 4.27 & 4.38 (2H, 2 x d, J = 5.9 Hz, NHCH2), 5.66 & 5.80 (1H, 2 x br., NH), 5.62 & 6.18 (1H, 2 x m, CH2CH = CH), 6.37 & 6.46 (1H, 2 x d, J = 15.9 & 11.7 Hz, CH2CH=CH), 6.88 (1H, 2 x d, J = 8.6 Hz, H8), 7.17–7.33 (5H, m, ArCH2´-6´), 7.36 & 7.41 (1H, 2 x dd, J = 8.6, 2.2 Hz, H7), 7.68 & 7.72 (1H, 2 x d, J = 2.1 Hz, H5); 13C NMR δ = 25.1 & 25.8 (CH2), 26.6 ((CH3)2), 27.8 & 32.4 (CH2), 35.9 & 35.9 (CH2), 42.6 & 42.7 (NHCH2), 48.8 (CH2C=O), 79.4 & 79.4 (C2), 118.9 & 119.0 (CH), 119.8 & 119.9 (ArC), 125.2 & 125.3 (CH), 126.0 (2 x CH), 126.7 & 127.0 (CH), 128.5 (2 x CH), 128.2 & 128.7 (CH), 129.7 & 130.8 (CH), 129.8 & 130.9 (ArC), 136.1 & 136.1 (CH), 137.4 & 137.5 (ArC), 159.4 & 159.4 (ArC), 172.6 & 172.7 (NHC=O), 192.5 (C4). HRMS (M-H)+ 376.1906, C24H26NO3 requires 376.1913.

N-((2,2-dimethyl-4-oxochroman-6-yl)methyl)-7-phenylhept-6-enamide, 1.5:1 E/Z (24h)

65 mg (0.32 mmol) of 23 was reacted as for 24a with 28h (65 mg, 0.32 mmol) to afford amide 24h. Pale oil, yield: 27%; IR (neat): 3284, 2925, 1686, 1644, 1616, 1538, 1487, 1436, 1255, 1189, 983 cm−1. 1H NMR (CDCl3, 400 MHz) δ = 1.45 & 1.45 (6H, 2 x s, C(CH3)2), 1.51 (2H, m, CH2), 1.69 (2H, m, CH2), 2.15–2.38 (4H, m, (CH2)2), 2.70 & 2.71 (2H, 2 x s, CH2C = O), 4.36 & 4.39 (2H, 2 x d, J = 5.7 Hz, NHCH2), 5.65 & 5.73 (1H, 2 x br., NH), 5.64 & 6.20 (1H, 2 x m, CH2CH = CH), 6.37 & 6.42 (1H, 2 x d, J ~ 16 & 11.6 Hz, CH2CH = CH), 6.90 (1H, 2 x d, J = 8.6 Hz, H8), 7.17–7.34 (5H, m, ArCH2´-6´), 7.42 (1H, 2 x dd, J = 8.4, 2.4 Hz, H7), 7.72 (1H, m, H5); 13C NMR δ = 25.2 & 25.3 (CH2), 26.6 ((CH3)2), 28.1 & 32.8 (CH2), 29.0 & 29.4 (CH2), 36.5 & 36.6 (CH2), 42.7 & 42.7 (NHCH2), 48.8 (CH2C=O), 79.4 (C2), 119.0 (CH), 120.0 (ArC), 125.3 (CH), 126.0 (2 x CH), 126.5 & 126.9 (CH), 128.5 (2 x CH), 128.2 & 128.7 (CH), 129.2 & 130.2 (ArC), 130.4 & 130.9 (CH), 136.1 (CH), 137.6 & 137.7 (ArC), 159.4 (ArC), 172.8 & 172.8 (NHC=O), 192.5 (C4). HRMS (M+Na)+ 414.2040, C25H29NO3Na requires 414.2045.

N-((2,2-dimethyl-4-oxochroman-6-yl)methyl)-8-phenyloct-7-enamide, 1:1 E/Z (24i)

51 mg (0.25 mmol) of 23 was reacted as for 24a with 28i (50 mg, 0.23 mmol) to afford amide 24i. Semi-solid gum, yield: 22%; IR (neat): 2927, 1689, 1644, 1617, 1539, 1488, 1434, 1258, 11882 cm−1. 1H NMR (CDCl3, 400 MHz) δ = 1.32–1.53 (4H, m, CH2, signal overlap), 1.45 (6H, s, C(CH3)2), 1.61–1.73 (2H, m, CH2), 2.17–2.38 (4H, m, (CH2)2), 2.71 (2H, s, CH2C=O), 4.38 (2H, m, NHCH2), 5.70 (1H, br., NH), 5.64 & 6.20 (1H, 2 x m, CH2CH=CH), 6.39 (1H, m, CH2CH=CH), 6.90 (1H, d, J = 8.6 Hz, H8), 7.17–7.35 (5H, m, ArCH2´-6´), 7.42 (1H, dd, H7), 7.72 (1H, d, H5); 13C NMR δ = 25.5 (CH2), 26.6 ((CH3)2), 28.4 (CH2), 26.9(CH2), 29.6(CH2), 36.7 (CH2), 42.7 (NHCH2), 48.8 (CH2C=O), 79.3 (C2), 118.9 (ArCH), 119.8 (ArC), 125.2 (ArCH), 125.9 (ArCH), 126.5 (ArCH), 128.1 (ArCH), 128.5 (ArCH), 128.7 (ArCH), 129.9 (CH=CH), 130.8 (CH=CH), 132.8 (ArC), 136.0 (ArCH), 137.7 (ArC), 159.4 (ArC), 172.9 (NHC=O), 192.5 (C4). HRMS (M+Na)+ 428.2197, C26H31NO3Na requires 428.2202.

Biologic activityAntileishmanial activity on L. infantum axenic amastigotes

L. infantum promastigotes (MHOM/MA/67/ITMAP-263, CNR Leishmania, Montpellier, France, expressing luciferase activity) were cultivated in RPMI 1640 medium supplemented with 10% foetal calf serum (FCS), 2 mM L-glutamine and antibiotics (100 U/mL penicillin and 100 μg/mL streptomycin) and harvested in the logarithmic phase of growth by centrifugation at 900 g for 10 min. The supernatant was carefully removed and replaced by the same volume of RPMI 1640 complete medium at pH 5.4, and then incubated for 24 h at 24 °C. The acidified promastigotes were then incubated for 24 h at 37 °C in a ventilated flask to transform promastigotes into axenic amastigotes. The effects of the tested compounds on the growth of L. infantum axenic amastigotes were assessed as follows. L. infantum amastigotes were incubated at a density of 2 × 106 parasites/mL in sterile 96-well plates with various concentrations of compounds dissolved in DMSO (final con-centration less than 0.5% v/v), in duplicate. Appropriate controls, DMSO and amphotericin, were added to each set of experiments. After a 48 h incubation period at 37 °C, each plate-well was then microscopically-examined to detect any precipitate formation. To estimate the luciferase activity of axenic amastigotes, 80 μL of each well were transferred to white 96-well plates, Steady Glow® reagent (Promega) was added according to the manufacturer’s instructions, and plates were incubated for 2 min. The luminescence was measured using a Microbeta Luminescence Counter (PerkinElmer). The inhibitory concentration 50% (IC50) was defined as the concentration of drug required to inhibit by 50% the metabolic activity of L. infantum amastigotes compared to control. IC50 values were calculated by non-linear regression analysis on dose response curves, using TableCurve 2D V5 software. IC50 values represent the mean of three independent experiments.

Cytotoxicity evaluation on J774A.1 cells

Evaluation of the cytotoxicity of test compounds was performed by MTT assay using the J774A.1 cell line (mouse macrophage cell line, Sigma-Aldrich). Briefly, cells (5 × 104 cells/mL) in 100 μL of complete medium, [DMEM High glucose supplemented with 10% fetal calf serum (FCS), 2 mM L-glutamine and antibiotics (100 U/mL penicillin and 100 µg/mL streptomycin)] were seeded into each well of 96-well plates and incubated at 37 °C in a humidified 5% CO2 with 95% air atmosphere. After 24 h incubation, 100 µL of medium with various product concentrations and appropriate controls were added and the plates were incubated for 72 h at 37 °C. Each plate-well was then examined under the microscope to detect possible precipitate formation before the medium was aspirated from the wells. 100 µL of MTT solution (0.5 mg/mL in RPMI) was then added to each well. Cells were incubated for 2 h at 37 °C. After this time, the MTT solution was removed and DMSO (100 µL) was added to dissolve the resulting formazan crystals. Plates were shaken vigorously (300 rpm) for 5 min. The absorbance was measured at 570 nm with a microplate spectrophotometer. DMSO was used as blank and doxorubicin (Sigma Aldrich) as positive control. CC50 values were calculated by non-linear regression analysis on dose–response curves, using TableCurve 2D V5 software.