3.1.3. General Procedure for the EDC-Mediated Esterification of Arecaidine (8a−c, 9a−c, 15a−c, 16a−c, 21, 25, 27)
To a heterogeneous mixture of arecaidine (1.0 equiv) and alcohol (1.5 equiv) in anhydrous CH2Cl2 (0.5 M) were added EDC-HCl (2.0 equiv) and 4-DMAP (0.5 equiv). The resulting mixture was vigorously stirred for 2 d. Then, the turbid mixture was poured into sat. aq. NaHCO3 and extracted with CH2Cl2 (3×). The combined organic layers were dried (Na2SO4) and concentrated under reduced pressure. The crude residue was purified by flash column chromatography to give the desired ester.
2-(hydroxymethyl)benzyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (8a). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 1,2-benzenedimethanol (7a). Purification by flash column chromatography (0–12% MeOH in CH2Cl2) afforded the title compound 8a (51 mg, 78%) as a pale orange solid. mp 75–77 °C. 1H NMR (400 MHz, CDCl3) δ 7.42 (m, 1H, Ph H-3), 7.37 (m, 1H, Ph H-6), 7.33 (m, 1H, Ph H-4), 7.29 (m, 1H, Ph H-5), 7.01 (m, 1H, H-4) 5.27 (s, 2H, (CO)OCH2), 4.72 (s, 2H, CH2OH), 3.3–2.9 (br s, 1H, OH), 3.12 (m, 2H, H-2), 2.48 (t, J = 5.6 Hz, 3H, H-6), 2.37 (s, 3H, NCH3), 2.35 (m, 2H, H-5). 13C NMR (100 MHz, CDCl3) δ 165.4 (C=O), 139.4 (Ph C-2), 138.2 (C-4), 133.7 (Ph C-1), 129.4 (Ph C-6), 128.7 (Ph C-34), 128.4 (Ph C-3), 128.6 (C-3), 127.9 (Ph C-5), 63.8 ((CO)OCH2), 62.6 (CH2OH), 53.0 (C-2), 50.6 (C-6), 45.5 (NCH3), 26.5 (C-5). IR (film) νmax 2943, 1709, 1454, 1398, 1290, 1263, 1139, 1087, 1046, 1026, 759. HRMS (ESI) (m/z) calcd for C15H20NO3 [M + H]+: 262.1438; found 262.1445.
3-(hydroxymethyl)benzyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (8b). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 1,3-benzenedimethanol (7b). Purification by flash column chromatography (0–12% MeOH in CH2Cl2) afforded the title compound 8b (54 mg, 83%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.32 (m, 1H, Ph H-2), 7.31 (m, 1H, Ph H-5), 7.29 (m, 1H, Ph H-4), 7.24 (m, 1H, Ph H-6), 7.01 (m, 1H, H-4), 5.14 (s, 2H, (CO)OCH2), 4.64 (s, 3H, CH2OH), 3.26 (br s, 1H, OH), 3.12 (m, 2H, H-2), 2.47 (t, J = 5.6 Hz, 3H, H-6), 2.36 (s, 3H, NCH3), 2.34 (m, 2H, H-5). 13C NMR (100 MHz, CDCl3) δ 165.4 (C=O), 141.7 (Ph C-3), 138.0 (C-4), 136.2 (Ph C-1), 128.6 (Ph C-5), 128.5 (C-3), 127.0 (Ph C-6), 126.6 (Ph C-4), 126.4 (Ph C-2), 66.0 ((CO)OCH2), 64.7 (CH2OH), 52.9 (C-2), 50.6 (C-6), 45.5 (NCH3), 26.3 (C-5). 1IR (film) νmax 1706, 1450, 1290, 1261, 1138, 1129, 1088, 1046, 1026, 999, 790, 719, 700. HRMS (ESI) (m/z) calcd for C15H20NO3 [M + H]+: 262.1438; found 262.1434.
4-(hydroxymethyl)benzyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (8c). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 1,4-benzenedimethanol (7c). Purification by flash column chromatography (0–12% MeOH in CH2Cl2) afforded the title compound 8c (48 mg, 73%) as a pale orange semi-solid. 1H NMR (400 MHz, CDCl3) δ 7.32 (m, 2H, Ph H-3,5), 7.31 (m, 2H, Ph H-2,6), 7.01 (m, 1H, H-4), 5.14 (s, 2H, (CO)OCH2), 4.64 (s, 2H, CH2OH), 3.26 (br s, 1H, OH), 3.12 (m, 2H, H-2), 2.47 (t, J = 5.7 Hz, 3H, H-6), 2.36 (s, 3H, NCH3), 2.34 (m, 2H, H-5). 13C NMR (100 MHz, CDCl3) δ 165.4 (C=O), 141.3 (Ph C-4), 138.0 (C-4), 135.1 (Ph C-1), 128.6 (C-3), 128.2 (Ph-2,6), 126.9 (Ph C-3,5), 65.9 ((CO)OCH2), 64.6 (CH2OH), 52.9 (C-2), 50.6 (C-6), 45.5 (NCH3), 26.3 (C-5). IR (film) νmax 1705, 1654, 1459, 1398, 1259, 1128, 1087, 1018, 790, 717. HRMS (ESI) (m/z) calcd for C15H20NO3 [M + H]+: 262.1438; found 262.1435.
(2-(((tert-butyldimethylsilyl)oxy)methyl)phenyl)(phenyl)methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (9a). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 6a. Purification by flash column chromatography (0–6% MeOH in CH2Cl2) afforded the title compound 9a (82 mg, 73%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.51 (m, 1H, Ph H-3), 7.41 (m, 1H, Ph H-6), 7.33 (m, 1H, Ph H-4), 7.30 (m, 5H, Ph H-2′,3′,4′,5′,6′), 7.29 (m, 1H, Ph H-5), 7.17 (s, 1H, CHPh2), 7.14 (m, 1H, H-4), 4.80 (d, J = 13.3 Hz, 1H, CH2OSi), 4.73 (d, J = 13.3 Hz, 1H, CH2OSi), 3.30 (m, 2H, H-2), 2.61 (m, 2H, H-6), 2.49 (s, 3H, NCH3), 2.47 (m, 2H, H-5), 0.90 (s, 9H, C(CH3)3), −0.03 (s, 3H, SiCH3), −0.04 (s, 3H, SiCH3). 13C NMR (100 MHz, CDCl3) δ 164.5 (C=O), 139.6 (Ph C-1′), 138.9 (Ph C-2), 138.2 (C-4), 137.0 (Ph C-1), 128.9 (C-3), 128.3 (Ph C-3′,5′), 128.1 (Ph C-4), 127.8 (Ph C-4′), 127.4 (Ph C-6), 127.3 (Ph C-5; Ph C-2′,6′), 127.0 (Ph C-3), 73.5 (CHPh2), 62.7 (CH2OSi), 53.2 (C-2), 50.8 (C-6), 45.7 (NCH3), 26.7 (C-5), 25.9 (C(CH3)3), 18.4 (C(CH3)3), −5.38 (SiCH3), −5.40 (SiCH3). IR (film) νmax 2928, 1710, 1462, 1251, 1189, 1140, 1115, 1075, 1024, 998, 970, 834, 775, 757, 718, 697. HRMS (ESI) (m/z) calcd for C27H38NO3Si [M + H]+: 452.2615; found 452.2621.
(3-(((tert-butyldimethylsilyl)oxy)methyl)phenyl)(phenyl)methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (9b). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 6b. Purification by flash column chromatography (0–6% MeOH in CH2Cl2) afforded the title compound 9b (89 mg, 79%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.35 (m, 2H, Ph H-2′,6′), 7.33 (m, 2H, Ph H-3′,5′), 7.32 (m, 1H, Ph H-2), 7.29 (m, 1H, Ph H-5), 7.27 (m, 1H, Ph H-4′), 7.24 (m, 2H, Ph H-4,6), 7.16 (m, 1H, H-4), 6.94 (s, 1H, CHPh2), 4.72 (s, 2H, CH2OSi), 3.29 (m, 2H, H-2), 2.60 (m, 2H, H-6), 2.48 (s, 3H, NCH3), 2.46 (m, 2H, H-5), 0.90 (s, 9H, C(CH3)3), 0.06 (s, 6H, Si(CH3)2). 13C NMR (100 MHz, CDCl3) δ 164.6 (C=O), 141.8 (Ph C-3), 140.4 (Ph C-1), 140.3 (Ph C-1′), 138.2 (C-4), 129.0 (C-3), 128.5 (Ph C-3′,5′), 128.4 (Ph C-5), 127.8 (Ph C-4′), 127.1 (Ph C-2′,6′), 125.7 (Ph C-4,6), 124.6 (Ph C-2), 76.7 (CHPh2), 64.8 (CH2OSi), 53.2 (C-2), 50.8 (C-6), 45.7 (NCH3), 26.7 (C-5), 26.0 (C(CH3)3), 18.4 (C(CH3)3), −5.3 (Si(CH3)2). IR (film) νmax 2928, 1711, 1252, 1140, 1081, 1025, 836, 777, 700. HRMS (ESI) (m/z) calcd for C27H38NO3Si [M + H]+: 452.2615; found 452.2624.
(4-(((tert-butyldimethylsilyl)oxy)methyl)phenyl)(phenyl)methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (9c). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 6c. Purification by flash column chromatography (0–6% MeOH in CH2Cl2) afforded the title compound 9c (79 mg, 70%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.34 (m, 2H, Ph H-2′,6′), 7.33 (m, 2H, Ph H-3′,5′), 7.32 (m, 2H, Ph H-2,6), 7.31 (m, 2H, Ph H-3,5), 7.27 (m, 1H, Ph H-4′), 7.18 (m, 1H, H-4), 6.93 (s, 1H, CHPh2), 4.72 (s, 2H, CH2OSi), 3.34 (m, 2H, H-2), 2.64 (m, 2H, H-6), 2.51 (s, 3H, NCH3), 2.48 (m, 2H, H-5), 0.93 (s, 9H, C(CH3)3), 0.09 (s, 6H, Si(CH3)2). 13C NMR (100 MHz, CDCl3) δ 164.7 (C=O), 141.2 (Ph C-4), 140.4 (Ph C-1′), 138.9 (Ph C-1), 138.2 (C-4), 129.0 (C-3), 128.5 (Ph C-3′,5′), 127.8 (Ph C-4′), 127.0 (Ph C-2,6; Ph C-2′,6′), 126.1 (Ph C-3,5), 76.5 (CHPh2), 64.6 (CH2OSi), 53.2 (C-2), 50.8 (C-6), 45.7 (NCH3), 26.7 (C-5), 26.0 (C(CH3)3), 18.4 (C(CH3)3), −5.3 (Si(CH3)2). IR (film) νmax 2928, 1711, 1252, 1140, 1084, 1024, 837, 776, 698. HRMS (ESI) (m/z) calcd for C27H38NO3Si [M + H]+: 452.2615; found 452.2625.
(2-((tert-butyldimethylsilyl)oxy)phenyl)(phenyl)methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (15a). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 13a. Purification by flash column chromatography (0–6% MeOH in CH2Cl2) afforded the title compound 15a (85 mg, 78%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.38 (dd, J = 7.7, 1.8 Hz, 1H, Ph H-6), 7.34 (s, 1H, CHPh2), 7.32 (m, 2H, Ph H-2′,6′), 7.30 (m, 2H, Ph H-3′,5′), 7.24 (m, 1H, Ph H-4′), 7.18 (m, 1H, Ph H-4), 7.14 (m, 1H, H-4), 6.96 (m, 1H, Ph H-5), 6.84 (dd, J = 8.1, 1.1 Hz, 1H, Ph H-3), 3.22 (m, 2H, H-2), 2.50 (m, 2H, H-6), 2.41 (s, 3H, NCH3), 2.38 (m, 2H, H-5), 0.97 (s, 9H, C(CH3)3), 0.29 (s, 3H, SiCH3), 0.21 (s, 3H, SiCH3). 13C NMR (100 MHz, CDCl3) δ 164.4 (C=O), 152.7 (Ph C-2), 140.2 (Ph C-1′), 137.7 (C-4), 130.7 (Ph C-1), 129.0 (C-3), 128.6 (Ph C-4), 128.2 (Ph C-3′,5′), 127.7 (Ph C-6), 127.5 (Ph C-4′), 127.0 (Ph C-2′,6′), 121.0 (Ph C-5), 118.4 (Ph C-3), 71.4 (CHPh2), 53.1 (C-2), 50.7 (C-6), 45.6 (NCH3), 26.5 (C-5), 25.7 (C(CH3)3), 18.2 (C(CH3)3), −4.13 (SiCH3), −4.18 (SiCH3). IR (film) νmax 2930, 1713, 1489, 1454, 1254, 1141, 1025, 921, 839, 783, 697. HRMS (ESI) (m/z) calcd for C26H36NO3Si [M + H]+: 438.2459; found 438.2461.
(3-((tert-butyldimethylsilyl)oxy)phenyl)(phenyl)methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (15b). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 13b. Purification by flash column chromatography (0–6% MeOH in CH2Cl2) afforded the title compound 15b (92 mg, 84%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.34 (m, 2H, Ph H-2′,6′), 7.33 (m, 2H, Ph H-3′,5′), 7.27 (m, 1H, Ph H-4′), 7.19 (m, 1H, Ph H-5), 7.15 (m, 1H, H-4), 6.93 (m, 1H, Ph H-6), 6.89 (s, 1H, CHPh2), 6.84 (m, 1H, Ph H-2), 6.76 (m, 1H, Ph H-4), 3.22 (m, 2H, H-2), 2.51 (m, 2H, H-6), 2.43 (s, 3H, NCH3), 2.40 (m, 2H, H-5), 0.97 (s, 9H, C(CH3)3), 0.17 (s, 6H, Si(CH3)2). 13C NMR (100 MHz, CDCl3) δ 164.5 (C=O), 155.7 (Ph C-3), 141.7 (Ph C-1), 140.2 (Ph C-1′), 138.2 (C-4), 129.4 (Ph C-5), 129.0 (C-3), 128.4 (Ph C-3′,5′), 127.8 (Ph C-4′), 127.0 (Ph C-2′,6′), 119.9 (Ph C-6), 119.5 (Ph C-4), 118.7 (Ph C-2), 76.4 (CHPh2), 53.2 (C-2), 50.7 (C-6), 45.7 (NCH3), 26.6 (C-5), 25.5 (C(CH3)3), 18.2 (C(CH3)3), −4.47 (SiCH3), −4.49 (SiCH3). IR (film) νmax 2930, 1714, 1602, 1486, 1253, 1141, 1084, 1026, 838, 784, 699. HRMS (ESI) (m/z) calcd for C26H36NO3Si [M + H]+: 438.2459; found 438.2464.
(4-((tert-butyldimethylsilyl)oxy)phenyl)(phenyl)methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (15c). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 13c. Purification by flash column chromatography (0–6% MeOH in CH2Cl2) afforded the title compound 15c (94 mg, 86%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.33 (m, 4H, Ph H-2′,3′,5′,6′), 7.27 (m, 1H, Ph H-4′), 7.21 (m, 2H, Ph H-2,6), 7.14 (m, 1H, H-4), 6.93 (s, 1H, CHPh2), 6.80 (m, 2H, Ph H-3,5), 3.22 (m, 2H, H-2), 2.51 (m, 2H, H-6), 2.42 (s, 3H, NCH3), 2.39 (m, 2H, H-5), 0.98 (s, 9H, C(CH3)3), 0.20 (s, 6H, Si(CH3)2). 13C NMR (100 MHz, CDCl3) δ 164.6 (C=O), 155.3 (Ph C-4), 140.5 (Ph C-1′), 138.0 (C-4), 132.9 (Ph C-1), 129.0 (C-3), 128.4 (Ph C-2,6), 128.3 (Ph C-3′,5′), 127.6 (Ph C-4′), 126.8 (Ph C-2′,6′), 119.8 (Ph C-3,5), 76.3 (CHPh2), 53.1 (C-2), 50.7 (C-6), 45.6 (NCH3), 26.6 (C-5), 25.6 (C(CH3)3), 18.0 (C(CH3)3), −4.5 (Si(CH3)2). IR (film) νmax 1711, 1509, 1252, 1189, 1140, 1083, 1025, 913, 839, 781, 699. HRMS (ESI) (m/z) calcd for C26H36NO3Si [M + H]+: 438.2459; found 438.2461.
2-((tert-butyldimethylsilyl)oxy)benzyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (16a). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 14a. Purification by flash column chromatography (0–6% MeOH in CH2Cl2) afforded the title compound 16a (72 mg, 80%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.31 (m, 1H, Ph H-6), 7.19 (m, 1H, Ph H-4), 7.02 (m, 1H, H-4), 6.93 (m, 1H, Ph H-5), 6.81 (m, 1H, Ph H-3), 5.20 (s, 2H, OCH2), 3.16 (m, 2H, H-2), 2.48 (m, 2H, H-6), 2.39 (s, 3H, NCH3), 2.35 (m, 2H, H-5), 1.00 (s, 9H, C(CH3)3), 0.24 (s, 6H, Si(CH3)2). 13C NMR (100 MHz, CDCl3) δ 165.6 (C=O), 153.8 (Ph C-2), 137.5 (C-4), 129.9 (Ph C-6), 129.2 (Ph C-4), 129.0 (C-3), 126.7 (Ph C-1), 121.0 (Ph C-5), 118.4 (Ph C-3), 61.9 (OCH2), 53.2 (C-2), 50.7 (C-6), 45.6 (NCH3), 26.5 (C-5), 25.6 (C(CH3)3), −4.3 (Si(CH3)2). IR (film) νmax 2931, 1712, 1492, 1456, 1256, 1141, 1086, 1027, 921, 838, 782. HRMS (ESI) (m/z) calcd for C20H32NO3Si [M + H]+: 362.2146; found 362.2165.
3-((tert-butyldimethylsilyl)oxy)benzyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (16b). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 14b. Purification by flash column chromatography (0–6% MeOH in CH2Cl2) afforded the title compound 16b (73 mg, 81%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.20 (m, 1H, Ph H-5), 7.05 (m, 1H, H-4), 6.93 (m, 1H, Ph H-6), 6.83 (m, 1H, Ph H-2), 6.78 (m, 1H, Ph H-4), 5.12 (s, 2H, OCH2), 3.17 (m, 2H, H-2), 2.49 (m, 2H, H-6), 2.40 (s, 3H, NCH3), 2.36 (m, 2H, H-5), 0.98 (s, 9H, C(CH3)3), 0.19 (s, 6H, Si(CH3)2). 13C NMR (100 MHz, CDCl3) δ 165.4 (C=O), 155.7 (Ph C-3), 137.9 (C-4), 137.5 (Ph C-1), 129.4 (Ph C-5), 128.9 (C-3), 120.7 (Ph C-6), 119.7 (Ph C-4), 119.5 (Ph C-2), 65.8 (OCH2), 53.2 (C-2), 50.7 (C-6), 45.7 (NCH3), 26.6 (C-5), 25.6 (C(CH3)3), −4.5 (Si(CH3)2). IR (film) νmax 2930, 1712, 1588, 1487, 1444, 1257, 1141, 1089, 1030, 959, 839, 782, 693. HRMS (ESI) (m/z) calcd for C20H32NO3Si [M + H]+: 362.2146; found 362.2166.
4-((tert-butyldimethylsilyl)oxy)benzyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (16c). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 14c. Purification by flash column chromatography (0–6% MeOH in CH2Cl2) afforded the title compound 16c (80 mg, 89%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.22 (m, 2H, Ph H-2,6), 7.02 (m, 1H, H-4), 6.80 (m, 2H, Ph H-3,5), 5.10 (s, 2H, OCH2), 3.15 (m, 2H, H-2), 2.47 (m, 2H, H-6), 2.39 (s, 3H, NCH3), 2.35 (m, 2H, H-5), 0.97 (s, 9H, C(CH3)3), 0.19 (s, 6H, Si(CH3)2). 13C NMR (100 MHz, CDCl3) δ 165.6 (C=O), 155.6 (Ph C-4), 137.7 (C-4), 129.7 (Ph C-2,6), 129.0 (C-3), 128.8 (Ph C-1), 120.0 (Ph C-3,5), 65.8 (OCH2), 53.1 (C-2), 50.7 (C-6), 45.7 (NCH3), 26.6 (C-5), 25.6 (C(CH3)3), −4.5 (Si(CH3)2). IR (film) νmax 2931, 1712, 1512, 1254, 1141, 1086, 1028, 914, 839, 781. HRMS (ESI) (m/z) calcd for C20H32NO3Si [M + H]+: 362.2146; found 362.2166.
2-((tert-butyldimethylsilyl)oxy)-1-phenylethyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (21). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 20. Purification by flash column chromatography (0–6% MeOH in CH2Cl2) afforded the title compound 21 (71 mg, 76%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.33 (m, 2H, Ph H-2,6), 7.32 (m, 2H, Ph H-3,5), 7.28 (m, 1H, Ph H-4), 7.08 (m, 1H, H-4), 5.89 (dd, J = 7.3, 4.6 Hz, 1H, CHCH2OH), 3.89 (dd, J = 10.9, 7.3 Hz, 1H, CHCH2OH), 3.80 (dd, J = 10.9, 4.6 Hz, 1H, CH2), 3.18 (m, 2H, H-2), 2.48 (m, 2H, H-6), 2.40 (s, 3H, NCH3), 2.37 (m, 2H, H-5), 0.84 (s, 9H, C(CH3)3), −0.02 (s, 6H, Si(CH3)2). 13C NMR (100 MHz, CDCl3) δ 164.8 (C=O), 137.9 (Ph C-1), 137.6 (C-4), 129.1 (C-3), 128.2 (Ph C-3,5), 127.9 (Ph C-4), 126.6 (Ph C-2,6), 76.2 (CHCH2OH), 66.1 (CHCH2OH), 5h3.2 (C-2), 50.7 (C-6), 45.6 (NCH3), 26.5 (C-5), 25.7 (C(CH3)3), 18.1 (C(CH3)3), –5.55 (SiCH3), −5.59 (SiCH3). IR (film) νmax 2928, 1713, 1253, 1128, 1088, 1027, 835, 777, 699. HRMS (ESI) (m/z) calcd for C21H34NO3Si [M + H]+: 376.2302; found 376.2302.
2-hydroxy-2,2-diphenylethyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (25). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 24. Purification by flash column chromatography (0–10% MeOH in CH2Cl2) afforded the title compound 25 (58 mg, 69%) as a colorless solid. mp 150–153 °C. 1H NMR (400 MHz, CDCl3) δ 7.41 (m, 4H, Ph H-2,6), 7.32 (m, 4H, Ph H-3,5), 7.25 (m, 2H, Ph H-4), 6.85 (m, 1H, H-4), 4.71 (s, 2H, (CO)OCH2), 3.46 (br s, 1H, OH), 3.02 (m, 2H, H-2), 2.45 (m, 2H, H-6), 2.33 (s, 3H, NCH3), 2.29 (m, 2H, H-5). 13C NMR (100 MHz, CDCl3) δ 165.4 (C=O), 143.7 (Ph C-1), 138.4 (C-4), 128.3 (C-3), 128.2 (Ph C-3,5), 127.4 (Ph C-4), 126.4 (Ph C-2,6), 77.3 (CPh2), 70.0 ((CO)OCH2), 52.8 (C-2), 50.5 (C-6), 45.4 (NCH3), 26.4 (C-5). IR (film) νmax 2797, 1707, 1449, 1262, 1140, 1094, 1028, 700. HRMS (ESI) (m/z) calcd for C21H24NO3 [M + H]+: 338.1751; found 338.1764.
2′-hydroxy-[1,1′-biphenyl]-2-yl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (27). Following the general procedure on a 0.25 mmol scale, arecaidine was esterified using 26. Purification by flash column chromatography (0–10% MeOH in CH2Cl2) afforded the title compound 27 (60 mg, 78%) as a pale orange solid. mp 142–144 °C. 1H NMR (400 MHz, CDCl3) δ 7.43 (m, 1H, Ph H-4), 7.39 (m, 1H, Ph H-6), 7.33 (m, 1H, Ph H-5), 7.24 (m, 1H, Ph H-3), 7.21 (m, 1H, Ph H-4′), 7.14 (dd, J = 7.6, 1.7 Hz, 1H, Ph H-6′), 7.02 (m, 1H, H-4), 6.92 (m, 1H, Ph H-5′), 6.80 (dd, J = 8.2, 1.0 Hz, 1H, Ph H-3′), 3.05 (m, 2H, H-2), 2.47 (t, J = 5.6 Hz, 2H, H-6) 2.35 (m, 2H, H-5), 2.33 (s, 3H, NCH3). 13C NMR (100 MHz, CDCl3) δ 164.0 (C=O), 153.6 (Ph C-2′), 148.5 (Ph C-2), 139.7 (C-4), 131.7 (Ph C-6), 130.9 (Ph C-6′), 130.7 (Ph C-1), 129.4 (Ph C-4′), 129.0 (Ph C-4), 127.9 (C-3), 126.3 (Ph C-5), 124.3 (Ph C-1′), 123.0 (Ph C-3), 120.1 (Ph C-5′), 115.9 (Ph C-3′), 52.7 (C-2), 50.5 (C-6), 45.4 (NCH3), 26.4 (C-5). IR (film) νmax 1730, 1440, 1235, 1191, 1122, 1045, 1013, 755. HRMS (ESI) (m/z) calcd for C19H20NO3 [M + H]+: 310.1438; found 310.1436.
3.1.4. General Procedure for the TBAF-Mediated TBS Deprotection of Arecaidine Esters (10a−c, 17b, 18b, 22)
To an ice-cooled solution of TBS-protected alcohol in anhydrous THF (0.2 M) was added TBAF (1.0 M in THF, 1.0 equiv) and it was stirred for 20 min at the indicated temperature. Then, volatiles were removed under reduced pressure and the crude residue was purified by flash column chromatography to give the desired deprotected alcohol.
(2-(hydroxymethyl)phenyl)(phenyl)methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (10a). Following the general procedure on a 0.10 mmol scale, 9a was deprotected. Purification by flash column chromatography (0–10% MeOH in CH2Cl2) afforded the title compound 10a (29 mg, 87%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.41 (m, 1H, Ph H-3), 7.39 (m, 1H, Ph H-6), 7.30 (m, 4H, Ph H-2′,3′,5′,6′), 7.29 (m, 2H, Ph H-4,5), 7.27 (m, 1H, Ph H-4′), 7.20 (s, 1H, CHPh2), 7.13 (m, 1H, H-4), 4.84 (d, J = 12.7 Hz, 1H, CH2OH), 4.63 (d, J = 12.7 Hz, 1H, CH2OH), 3.32 (br s, 1H, OH), 3.18 (m, 2H, H-2), 2.50 (m, 2H, H-6), 2.39 (s, 3H, NCH3), 2.38 (m, 2H, H-5). 13C NMR (100 MHz, CDCl3) δ 164.8 (C=O), 139.6 (Ph C-1′), 138.6 (Ph C-2; C-4), 137.9 (Ph C-1), 128.9 (Ph C-3), 128.6 (C-3), 128.43 (Ph C-3′,5′), 128.37 (Ph C-4), 128.2 (Ph C-5), 127.8 (Ph C-4′), 127.7 (Ph C-6), 126.9 (Ph C-2′,6′), 73.5 (CHPh2), 62.7 (CH2OH), 52.9 (C-2), 50.6 (C-6), 45.5 (NCH3), 26.5 (C-5). IR (film) νmax 1708, 1452, 1245, 1190, 1138, 1085, 1022, 758, 699. HRMS (ESI) (m/z) calcd for C21H24NO3 [M + H]+: 338.1751; found 338.1756.
(3-(hydroxymethyl)phenyl)(phenyl)methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (10b). Following the general procedure on a 0.10 mmol scale, 9b was deprotected. Purification by flash column chromatography (0–10% MeOH in CH2Cl2) afforded the title compound 10b (29 mg, 86%) as a pale-yellow solid. mp 125–128 °C. 1H NMR (400 MHz, CDCl3) δ 7.33 (m, 2H, Ph H-2′,6′), 7.32 (m, 3H, Ph H-2; Ph H-3′,5′), 7.28 (m, 1H, Ph H-5), 7.27 (m, 1H, Ph H-4′), 7.25 (m, 2H, Ph H-4,6), 7.12 (m, 1H, H-4), 6.92 (s, 1H, CHPh2), 4.60 (s, 2H, CH2OH), 3.37 (br s, 1H, OH), 3.20 (m, 2H, H-2), 2.49 (m, 2H, H-6), 2.37 (s, 3H, NCH3), 2.37 (m, 2H, H-5). 13C NMR (100 MHz, CDCl3) δ 164.4 (C=O), 141.6 (Ph C-3), 140.5 (Ph C-1), 140.1 (Ph C-1′), 138.2 (C-4), 129.0 (C-3), 128.6 (Ph C-5), 128.5 (Ph C-3′,5′; C-3), 127.8 (Ph C-4′), 127.0 (Ph C-2′,6′), 126.4 (Ph C-4), 126.0 (Ph C-6), 125.4 (Ph C-2), 69.2 (CHPh2), 64.7 (CH2OH), 52.8 (C-2), 50.5 (C-6), 45.4 (NCH3), 26.3 (C-5). IR (film) νmax 1707, 1452, 1396, 1243, 1190, 1137, 1085, 1022, 787, 733, 698, 607. HRMS (ESI) (m/z) calcd for C21H24NO3 [M + H]+: 338.1751; found 338.1766.
(4-(hydroxymethyl)phenyl)(phenyl)methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (10c). Following the general procedure on a 0.10 mmol scale, 9c was deprotected. Purification by flash column chromatography (0–10% MeOH in CH2Cl2) afforded the title compound 10c (31 mg, 92%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.32 (m, 4H, Ph H-2′,3′,5′,6′), 7.30 (m, 4H, Ph H-2,3,5,6), 7.27 (m, 1H, Ph H-4′), 7.13 (m, 1H, H-4), 6.91 (s, 1H, CHPh2), 4.61 (s, 2H, CH2OH), 3.38 (br s, 1H, OH), 3.22 (m, 2H, H-2), 2.53 (m, 2H, H-6), 2.40 (s, 3H, NCH3), 2.39 (m, 2H, H-5). 13C NMR (100 MHz, CDCl3) δ 164.4 (C=O), 140.9 (Ph C-4), 140.1 (Ph C-1′), 139.4 (Ph C-1), 138.2 (C-4), 128.5 (Ph C-3′,5′), 128.4 (C-3), 127.9 (Ph C-4′), 127.2 (Ph C-2,6), 127.0 (Ph C-3,5), 126.9 (Ph C-2′,6′), 76.7 (CHPh2), 64.6 (CH2OH), 52.8 (C-2), 50.5 (C-6), 45.4 (NCH3), 26.2 (C-5). IR (film) νmax 1709, 1455, 1396, 1248, 1139, 1085, 1024, 699. HRMS (ESI) (m/z) calcd for C21H24NO3 [M + H]+: 338.1751; found 338.1765.
(3-hydroxyphenyl)(phenyl)methyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (17b). Following the general procedure on a 0.10 mmol scale, 15b was deprotected. Purification by flash column chromatography (0–10% MeOH in CH2Cl2) afforded the title compound 17b (29 mg, 90%) as an off-white solid. mp 143–144 °C. 1H NMR (400 MHz, CDCl3) δ 7.31 (m, 4H, Ph H-2′,3′,5′,6′), 7.26 (m, 1H, Ph H-4′), 7.11 (m, 1H, Ph H-5), 7.13 (m, 1H, H-4), 6.85 (s, 1H, CHPh2), 6.82 (m, 1H, Ph H-6), 6.74 (m, 1H, Ph H-2), 6.65 (m, 1H, Ph H-4), 3.28 (m, 2H, H-2), 2.56 (m, 2H, H-6), 2.41 (s, 3H, NCH3), 2.39 (m, 2H, H-5). 13C NMR (100 MHz, CDCl3) δ 164.4 (C=O), 156.3 (Ph C-3), 141.7 (Ph C-1), 140.0 (Ph C-1′), 138.3 (C-4), 129.7 (Ph C-5), 128.5 (Ph C-3′,5′), 128.2 (C-3), 127.9 (Ph C-4′), 127.0 (Ph C-2′,6′), 118.6 (Ph C-6), 115.1 (Ph C-4), 114.2 (Ph C-2), 76.8 (CHPh2), 52.7 (C-2), 50.4 (C-6), 45.2 (NCH3), 25.9 (C-5). IR (film) νmax 2949, 1710, 1588, 1453, 1248, 1127, 1086, 1022, 735, 701. HRMS (ESI) (m/z) calcd for C20H22NO3 [M + H]+: 324.1594; found 324.1588.
3-hydroxybenzyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (18b). Following the general procedure on a 0.10 mmol scale, 16b was deprotected. Purification by flash column chromatography (0–10% MeOH in CH2Cl2) afforded the title compound 18b (20 mg, 82%) as an off-white solid. mp 115–119 °C. 1H NMR (400 MHz, CDCl3) δ 8.84 (br s, 1H, OH), 7.15 (m, 1H, Ph H-5), 6.82 (m, 1H, H-6), 6.72 (m, 1H, Ph H-2), 6.71 (m, 1H, Ph H-4), 5.07 (s, 2H, OCH2), 3.28 (m, 2H, H-2), 2.59 (m, 2H, H-6), 2.45 (s, 3H, NCH3), 2.40 (m, 2H, H-5). 13C NMR (100 MHz, CDCl3) δ 165.3 (C=O), 157.0 (Ph C-3), 138.2 (C-4), 137.2 (C-1), 129.7 (Ph C-5), 128.0 (C-3), 119.3 (Ph C-6), 115.6 (Ph C-4), 115.2 (Ph C-2), 66.2 (OCH2), 52.6 (C-2), 50.4 (C-6), 45.2 (NCH3), 25.8 (C-5). IR (film) νmax 1707, 1589, 1458, 1398, 1261, 1127, 1089, 1026, 787, 719, 694. HRMS (ESI) (m/z) calcd for C14H18NO3 [M + H]+: 248.1281; found 248.1287.
2-hydroxy-1-phenylethyl 1-methyl-1,2,5,6-tetrahydropyridine-3-carboxylate (22). Following the general procedure on a 0.10 mmol scale, 21 was deprotected. Purification by flash column chromatography (0–10% MeOH in CH2Cl2) afforded the title compound 22 (17 mg, 65%) as a yellow oil. 1H NMR (400 MHz, CDCl3) δ 7.39 (m, 2H, Ph H-2,6), 7.36 (m, 2H, Ph H-3,5), 7.31 (m, 1H, Ph H-4), 7.04 (m, 1H, H-4), 4.98 (dd, J = 8.1, 3.5 Hz, 1H, CHCH2OH), 4.34 (dd, J = 11.5, 3.5 Hz, 1H, CHCH2OH), 4.24 (dd, J = 11.5, 8.1 Hz, 1H, CH2), 3.17 (m, 2H, H-2), 3.01 (br s, 1H, OH), 2.53 (m, 2H, H-6), 2.42 (s, 3H, NCH3), 2.40 (m, 2H, H-5). 13C NMR (100 MHz, CDCl3) δ 165.6 (C=O), 140.1 (Ph C-1), 138.3 (C-4), 128.5 (Ph C-3,5), 128.4 (C-3), 128.2 (Ph C-4), 126.1 (Ph C-2,6), 72.4 (CHCH2OH), 69.4 (CHCH2OH), 52.9 (C-2), 50.6 (C-6), 45.5 (NCH3), 26.4 (C-5). IR (film) νmax 1706, 1656, 1453, 1398, 1261, 1192, 1138, 1089, 1026, 790, 755, 701. HRMS (ESI) (m/z) calcd for C15H20NO3 [M + H]+: 262.1438; found 363.1432.