SUPPORTING INFORMATION FOR. Regioselective Ring-opening and Isomerization Reactions of 3,4-Epoxyesters Catalyzed by Boron Trifluoride

S1 SUPPORTING INFORMATION FOR Regioselective Ring-opening and Isomerization Reactions of 3,4-Epoxyesters Catalyzed by Boron Trifluoride Javier Izquierdo, Santiago Rodríguez and Florenci V. González* Departament de Química Inorgànica i Orgànica, Universitat Jaume I, 12080 Castelló, Spain

S2 TABLE OF CONTENTS General experimental S3 General experimental procedure for the syntheses of 3-ene carboxylic acids S3 General experimental procedure for the syntheses of 3-enoates S3 General experimental procedure for the syntheses of epoxides 1a-1e S4 Compound 1a-1e S4 Compound 1f S5 General experimental procedure for the syntheses of 3-ene-ketones S5 Compound 7 S5 Compound 8 and 9 S6 General experimental procedure for the opening of 3,4-epoxyesters with alcohols S6 Compounds 2a (R 3 = Me, i-pr, t-bu), 2b (R 3 = Me, Et) S6 Compounds 2b (R 3 = i-pr, t-bu, Bn), 2c (R 3 = Me, Bn), 2d (R 3 = Me), 2e (R 3 = Me) S7 General experimental procedure for the syntheses of ketoesters 4 S8 Compounds 4a-4c, 5 and 6 S8 Compound 10, 11 and 12 S9 1 H-NMR and 13 C-NMR spectra of 1a S10-S11 1 H-NMR and 13 C-NMR spectra of 1b S12-S13 1 H-NMR and 13 C-NMR spectra of 1c S14-S15 1 H-NMR and 13 C-NMR spectra of 1d S16-S17 1 H-NMR and 13 C-NMR spectra of 1e S18-S19 1 H-NMR and 13 C-NMR spectra of 1f S20-S21 1 H-NMR and 13 C-NMR spectra of 2a (R 3 = Me) S22-S23 1 H-NMR and 13 C-NMR spectra of 2a (R 3 = i-pr) S24-S25 1 H-NMR and 13 C-NMR spectra of 2a (R 3 = t-bu) S26-S27 1 H-NMR and 13 C-NMR spectra of 2b (R 3 = Me) S28-S29 1 H-NMR and 13 C-NMR spectra of 2b (R 3 = Et) S30-S31 1 H-NMR and 13 C-NMR spectra of 2b (R 3 = i-pr) S32-S33 1 H-NMR and 13 C-NMR spectra of 2b (R 3 = t-bu) S34-S35 1 H-NMR and 13 C-NMR spectra of 2b (R 3 = Bn) S36-S37 1 H-NMR and 13 C-NMR spectra of 2c (R 3 = Me) S38-S39 1 H-NMR and 13 C-NMR spectra of 2c (R 3 = Bn) S40-S41 1 H-NMR and 13 C-NMR spectra of 2d and 3d (R 3 = Me) S42-S43 1 H-NMR and 13 C-NMR spectra of 2e (R 3 = Me) S44-S45 1 H-NMR and 13 C-NMR spectra of 4a S46-S47 1 H-NMR and 13 C-NMR spectra of 4b S48-S49 1 H-NMR and 13 C-NMR spectra of 4c S50-S51 1 H-NMR and 13 C-NMR spectra of 5 S52-S53 1 H-NMR and 13 C-NMR spectra of 6 S54-S55 1 H-NMR and 13 C-NMR spectra of 7 S56-S57 1 H-NMR and 13 C-NMR spectra of 10 S58-S59 1 H-NMR and 13 C-NMR spectra of 11 S60-S61 1 H-NMR and 13 C-NMR spectra of 12 S62-S63

S3 Experimental procedures and characterization data General. 1 H NMR spectra and 13 C NMR spectra were measured in CDCl 3 ( 1 H, 7.24 ppm; 13 C 77.0 ppm) solution at 30 C on a 300 MHz or a 500 MHz NMR spectrometer. Mass spectra were measured in a QTOF I (quadrupole-hexapole-tof) mass spectrometer with an orthogonal Z-spray-electrospray interface. IR spectra were recorded as oily films on NaCl plates on a FT-IR spectrometer. EM Science Silica Gel 60 was used for column chromatography while TLC was performed precoated plates (Kieselgel 60, F 254, 0.25 mm). Unless otherwise specified, all reactions were carried out under nitrogen atmosphere with magnetic stirring. Syntheses of 3,4-epoxyesters 1a-1e Epoxyesters 1a-1e were prepared according to the following scheme: malonic acid + aldehyde 1. SiO 2, mw, 5' 2. R 2 OH, H + R 1 CO 2 R 2 mcpba R 1 CO 2 R 2 O 1a, R 1 = Me, R 2 = Me 1b, R 1 = Et, R 2 = Et 1c, R 1 = n-pr, R 2 = Et 1d, R 1 = Bn, R 2 = Me 1e, R 1 = Ph, R 2 = Me General experimental procedure for the syntheses of 3-ene carboxylic acids. 1 Aldehyde (14 mmol) and malonic acid (1.5g, 14 mmol) were mixed thoroughly with chromatography grade SiO 2 2 (200 mesh, 5 g) and the resulting powder in a pyrex test tube was subjected to microwave irradiation at an output of 600 watts for 4 periods of 1.5 min. The reaction mass was allowed to cool to room temperature and extracted with dichloromethane (30 ml). The crude oil was purified through chromatography (silica-gel, hexanes/etoac (7/3)). Spectroscopic data for (E)-hept-3-enoic acid (yield = 55%). 1 H NMR (300 MHz, CDCl 3 ) δ 11.36 (1H, s), 5.32-5.68 (2H, m), 3.06 (2H, d, J = 6.4 Hz), 1.93-2.15 (2H, m), 1.26-1.50 (2H, m), 0.75-0.99 (3H, m). 13 C NMR (75 MHz, CDCl 3 ) δ 179.2, 135.6, 121.2, 38.2, 34.1, 22.6, 13.9 ppm. IR (NaCl) δ 3120, 2962, 2932, 2871, 1715, 1413, 1289, 1227, 1172, 968, 924 cm -1. HRMS m/z calcd. for C 7 H 11 O 2 [M-H - ]: 127.0759, found: 127.0756. Spectroscopic data for (E)-5-phenylpent-3-enoic acid (yield = 72%). 1 H NMR (500 MHz, CDCl 3 ) δ 11.79 (s, 1H), 7.01-7.56 (5H, m), 5.83-5.91 (1H, m), 5.69-5.78 (1H, m), 3.46-3.54 (2H, d, J = 6.9 Hz), 3.19-3.25 (2H, d, J = 6.9 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 178.8, 140.1, 134.0, 128.7, 128.7, 126.4, 122.6, 39.1, 37.9 ppm. IR (NaCl) δ 3005, 1709, 1603, 1495, 1453, 1417, 1285, 1222, 1256, 1079, 1030, 969, 746, 698 cm -1. HRMS m/z calcd. for C 11 H 11 O 2 [M-H - ]: 175.0759, found: 175.0762. Spectroscopic data for (E)-4-phenylbut-3-enoic acid (yield = 81%). 1 H NMR (500 MHz, CDCl 3 ) δ 11.31 (s, 1H), 7.25-7.41 (5H, m), 6.54 (1H, m), 6.27-6.35 (m, 1H), 3.32 (2H, d, J = 7.1 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 178.5, 136.8, 134.1, 128.7, 127.8, 126.50, 121.0, 38.18 ppm. IR (NaCl) δ, 3024, 1701, 1494, 1442, 1403, 1325, 1297, 1226, 1179, 1067, 980, 918, 813, 743, 692 cm -1. HRMS m/z calcd. for C 10 H 9 O 2 [M-H - ]: 161.0603, found: 161.0609. General experimental procedure for the syntheses of 3-enoates. To an ice-bath cold solution of (E)-3-ene carboxylic acid (6.2 mmol) in the corresponding alcohol (7 ml) was added concentrated H 2 SO 4 (12 µl, 0.0002 mmol). The resulting mixture was stirred at room temperature (21 ºC) for 16 h. Then solid Na 2 CO 3 was added and stirred for 2 min. Then the solution was filtrated, washed with aqueous saturated NaHCO 3 (10 ml) and extracted with CH 2 Cl 2 (3 x 30 ml), the organic layers were washed (brine), dried (Na 2 SO 4 ) and concentrated. The crude oil was purified through chromatography (silica-gel, hexanes/etoac (7:3)) to afford the corresponding ester. Spectroscopic data for (E)-ethyl hept-3-enoate (yield = 82%). 1 H NMR (500 MHz, CDCl 3 ) δ 5.40-5.62 (2H, m), 4.13 (2H, q, J = 7.1 Hz), 2.97 (2H, d, J = 5.1 Hz), 1.99 (2H, q, J = 7.2 Hz), 1.31-1.45 (2H, m), 1.23 (3H, t, J = 7.1 Hz), 0.89 (3H, t, J = 7.2 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 172.6, 134.9, 122.1, 60.8, 38.5, 34.9, 22.6, 14.6, 13.9 ppm. IR (NaCl) δ 2958, 2932, 2875, 1742, 1464, 1373, 1253, 1165, 1035, 971 699 cm -1. HRMS m/z calcd. for C 9 H 16 O 2 Na [M+Na + ]: 156.1150, found: 156.1151. 1 Kumar, S. H. M.; Reddy, B. V. S.; Reddy, E. J.; Yadav, J. S. Tetrahedron Lett. 1999, 40, 2401.

S4 Spectroscopic data for (E)-methyl 4-phenylbut-3-enoate (yield = 76%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.19-7.45 (5H, m), 6.50 (1H, d, J = 16.0 Hz), 6.23-6.39 (m, 1H), 3.73 (3H, s), 3.18-3.35 (2H, m). 13 C NMR (125 MHz, CDCl 3 ) δ 172.1, 137.0, 133.9, 128.8, 128.4, 128.1, 127.1, 126.8, 121.9, 52.0, 38.5, 38.4, 38.3 ppm. IR (NaCl) δ 3083, 3024, 2999, 2952, 2901, 1739, 1501, 1434,1356, 1263, 1155, 1068, 968, 746, 693 cm -1. HRMS m/z calcd. for C 11 H 12 O 2 Na [M+Na + ]: 199.0735, found: 199.0733 Spectroscopic data for (E)-methyl 5-phenylpent-3-enoate (yield = 64%). 1 H NMR (300 MHz, CDCl 3 ) δ 7.06-7.45 (5H, m), 5.59-5.85 (2H, m), 3.71 (s, 3H), 3.45 (2H, d, J = 5.9 Hz), 3.11 (2H, d, J = 6.4 Hz). 13 C NMR (75 MHz, CDCl 3 ) δ 172.5, 140.3, 133.4, 128.7, 128.7, 128.6, 51.9, 39.1, 37.9 ppm. IR (NaCl) δ 3086, 3029, 3002, 2952, 2905, 2835, 1739, 1684, 1494, 1433,1356, 1249, 1155, 1078, 968, 746, 699 cm -1. HRMS m/z calcd. for C 12 H 14 O 2 Na [M+Na + ]: 213.0891, found: 213.0894 General experimental procedure for the syntheses of epoxides 1a-1e. To an ice-bath cold solution of (E)-3-enoate (8.50 mmol) in chloroform (80 ml) was added meta-chloroperbenzoic acid (85%) (2.60 g, 12.70 mmol). The resulting mixture was stirred at room temperature for 16 h and then potassium carbonate (2.5 g) was added in one portion and stirred for 30 min at room temperature, then was filtered, washed with a saturated sodium bicarbonate aqueous solution, brine (twice), dried (Na 2 SO 4 ) and concentrated. The crude oil was purified through chromatography (silica-gel, hexanes/etoac (8:2) and (7:3)). Spectroscopic data for methyl 3-hydroxy-4-methoxypentanoate 1a (yield = 85%). 1 H NMR (300 MHz, CDCl 3 ) δ 3.71 (3H, s), 3.00 (1H, td, J= 5.8, 2.1Hz), 2.82 (1H, qd, J= 5.2, 2.1Hz), 2.57 (1H, dd, J = 16.3, 6.0Hz), 2.53 (1H, dd, J = 16.3, 5.6 Hz), 1.32 (3H, d, J = 5.3 Hz). 13 C NMR (75 MHz, CDCl 3 ) δ 170.8, 54.7, 54.3, 51.8, 37.4, 17.2 ppm. HRMS m/z calcd. for C 6 H 11 O 3 [M+H + ]: 131.0708, found: 131.0707. Spectroscopic data for ethyl 2-(3-ethyloxiran-2-yl)acetate 1b (yield = 97%). 1 H NMR (500 MHz, CDCl 3 ) δ 4.07 (2H, q, J = 7.1 Hz), 2.93 (1H, td, J = 5.9, 1.9 Hz), 2.62 (1H, td, J = 1.9, 5.5 Hz), 2.47 (1H, dd, J = 16.2, 6.1 Hz), 2.40 (1H, dd, J = 16.2, 5.6 Hz), 1.57 1.38 (2H, m), 1.17 (3H, t, J = 7.1 Hz), 0.91 (3H, t, J = 7.4 Hz). 13 C NMR (125 MHz, CDCl 3 ) 170.2, 60.6, 59.4, 53.5, 37.8, 24.7, 14.0, 9.5 ppm. IR (NaCl) δ 2971, 2933, 2971, 2877, 1738, 1462, 1373, 1321, 1304, 1254, 1182, 1029, 948, 911, 888 cm -1. HRMS m/z calcd. for C 8 H 15 O 3 [M+H + ]: 159.1021, found: 159.1025; calcd. for C 8 H 14 O 3 Na [M+Na + ]: 181.0841, found: 181.0841. Spectroscopic data for ethyl 2-(3-propyloxiran-2-yl)acetate 1c (yield = 87%). 1 H NMR (500 MHz, CDCl 3 ) δ 3.91 (2H, q, J = 7.1 Hz), 2.76 (1H, m), 2.54 (1H, m), 2.28 (2H, m), 1.24 (4H, m), 1.01 (3H, t, J = 7.1 Hz), 0.71 (3H, t, J = 7.1 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 170.0, 60.3, 57.9, 53.6, 37.5, 33.5, 19.0, 13.9, 13.5. IR (NaCl) δ 2962, 2872, 1739, 1605, 1467, 1377, 1313, 1256, 1172, 1028, 944, 904, 860, 736 cm -1 HRMS m/z calcd. for C 9 H 17 O 3 [M+H + ]: 173.1178, found: 173.1178 Spectroscopic data for methyl 2-(3-benzyloxiran-2-yl)acetate 1d (yield = 63%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.23-7.35 (5H, m), 3.68 (3H, s), 3.16 (1H, dt, J = 2.0, 5.9 Hz), 2.99 (1H, dt, J = 2.0, 5.5 Hz), 2.92 (1H, dd, J = 5.6, 14.6 Hz), 2.86 (1H, dd, J = 5.4, 14.6 Hz), 2.60 (1H, dd, J = 6.2, 16.3 Hz), 2.55 (1H, dd, J = 5.7, 16.3 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 171.0, 137.2, 133.9, 129.2, 128.8, 126.9, 58.8, 54.2, 52.2, 38.3, 37.6. IR (NaCl) δ 3083, 3066, 3033, 3003, 2952, 2848, 1739, 1605, 1574, 1497, 1440, 1366, 1169, 1118, 1078, 994, 958, 854, 743, 699 cm -1 HRMS m/z calcd. for C 12 H 14 O 3 Na [M+Na + ]: 229.0841, found: 229.0838. Spectroscopic data for methyl 2-(3-phenyloxiran-2-yl)acetate 1e (yield = 87%). 1 H NMR (300 MHz, CDCl 3 ) δ 7.22-7.32 (5H, m), 3.69 (3H, s), 3.31 (2H, ddd, J = 2.0, 5.0, 6.7 Hz), 2.72 (1H, dd, J = 4.9, 16.4 Hz), 2.63 (1H, dd, J = 6.5, 16.4 Hz). 13 C NMR (75 MHz, CDCl 3 ) δ 170.6, 136.8, 128.5, 128.3, 125.7, 58.1, 57.9, 51.9, 37.6. IR (NaCl) δ 3086, 3066, 3026, 3003, 2956, 2848, 1742, 1605, 1575, 1494, 1477, 1367, 1256, 1165, 1102, 1001, 951, 870, 756, 699 cm -1 HRMS m/z calcd. for C 11 H 12 O 3 Na [M+Na + ]: 215.0684, found: 215.0684. Synthesis of 4,5-epoxyester 1f: Epoxyester 1f was prepared according to the following scheme: OHC CO 2 Et 1. Pd(OH) 2 /C, H 2, 98% mcpba Et Et CO 2 Et CHCl 3 O 2. PPh 3 I 72% 1f CO 2 Et BuLi, THF 59% Ethyl 4-oxobutanoate. To a stirred solution of ethyl 4-oxo-2-butenoate (3 g, 23.4 mmol) in 15 ml of AcOEt was added Pd(OH) 2 /C (300 mg). The resulting suspension was stirred under H 2 atmosphere for nine hours. Then it was filtrated through celite and concentrated to afford ethyl 4-oxobutanoate (2.95 g, 98%) as a colorless oil which was submitted to the next step without any further purification. 1 H NMR (300 MHz, CDCl 3 ) δ 9.74 (1H, s), 4.07 (2H, q, J = 7.1 Hz), 2.75 (2H, t, J= 6.6 Hz), 2.58 (2H, t, J= 6.6

S5 Hz), 1.22 (3H, t, J = 7.1 Hz). 13 C NMR (75 MHz, CDCl 3 ) δ 200.4, 172.5, 61.0, 38.7, 26.8, 14.3 ppm. IR (NaCl) δ 3480, 2984, 2939, 2733, 1792, 1732, 1662, 1447, 1375, 1349, 1179, 1035, 962, 935, 893, 855, 822, 790, 687 cm -1. (E)-Ethyl hept-4-enoate. To an ice-bath cold suspension of the n-propyl triphenyl phosphonium iodide (5.9 g, 15.4 mmol) in THF (40 ml) was added dropwise n-buli (1.6 M in hexanes) (10 ml, 16 mmol). The resulting solution was stirred for 1 h. Then a solution of ethyl 4-oxobutanoate (2 g, 15.4 mmol) in THF (7 ml) was added dropwise and the resulting mixture was stirred at room temperature (21 ºC) for 5 h. Then was quenched with brine and extracted with Et 2 O (3 x 30 ml), dried (Na 2 SO 4 ) and concentrated. The resulting mixture was treated with hexanes/et 2 O to afford a white solid (triphenylphosphine oxide) which was filtered off. The resulting solution was concentrated to afford (E)-ethyl hept-4-enoate (1.43 g, 59 %) as a yellowish oil. 1 H NMR (300 MHz, CDCl 3 ) δ 5.15-5.51 (2H, m), 4.10 (2H, q, J = 7.1 Hz), 2.19-2.49 (4H, m), 1.90-2.15 (2H, m), 1.21 (3H, t, J= 7.1 Hz), 0.94 (3H, t, J = 7.5 Hz). 13 C NMR (75 MHz, CDCl 3 ) δ 173.4, 132.3, 127.07, 60.5, 34.7, 28.2, 22.3, 20.7, 14.5 ppm. Ethyl 3-(3-ethyloxiran-2-yl)propanoate 1f. To an ice-bath cold solution of (E)-ethyl hept-4-enoate (1.43 g, 9.15 mmol) in chloroform (96 ml) was added meta-chloroperbenzoic acid (85%) (3.1 g, 13.7 mmol). The resulting mixture was stirred at room temperature for 16 h and then potassium carbonate (3 g) was added in one portion and stirred for 30 min at room temperature, then was filtered, washed with a saturated sodium bicarbonate solution, brine (twice), dried (Na 2 SO 4 ) and concentrated. The crude oil was purified through chromatography (silica-gel, hexanes/etoac (9:1) to afford compound 1f (1.12 g, 72%) as a colorless oil. 1 H NMR (500 MHz, CDCl 3 ) δ 4.09 (2H, q, J= 7.0 Hz), 2.90 (1H, m), 2.83 (1H, m), 2.35-2.45 (2H, m), 1.80-1.87 (1H, m), 1.68-1.75 (1H, m), 1.44-1.53 (2H, m), 1.20 (3H, t, J= 7.5 Hz), 0.98 (3H, t, J= 7.5 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 173.0, 60.7, 58.7, 56.3, 31.5, 23.5, 21.3, 14.4, 10.7 ppm. IR (NaCl) δ 2974, 2878, 1737, 1464, 1374, 1352, 1260, 1180, 1096, 1038, 908, cm -1. HRMS m/z calcd. for C 8 H 14 O 3 Na [M+Na + ]: 181.0841, found: 181.0842. Syntheses of 3,4-epoxyketones 7 and 8 Epoxyketones 7 and 8 were prepared according to the following scheme: R CO 2 H 1. MsOH, 2. EtMgBr O R O Et mcpba R O O 7, R = Bn 8, R = Ph Et General experimental procedure for the syntheses of 3-ene-ketones. To a -20 ºC cold solution of 3-ene carboxylic acid (4.06 mmol) (readily prepared as described above 2 ) in CH 2 Cl 2 (16 ml) was added methanesulfonic acid (1% in CH 2 Cl 2 ) (52 μl, 8 10-3 mmol) followed by 2,3-dihydrofuran (321 μl, 4.26 mmol). The resulting mixture was stirred at -20 ºC for 15 min and then in an icebath for 4 h. Then it was cold again at -20 ºC and ethyl magnesium bromide (3 M in THF) (1.35 ml, 4.05 mmol) was added dropwise for 5 min. The resulting mixture was stirre allowing to warm up to room temperature for 18 h. Then the reaction was cooled with an ice-bath and then quenched with H 3 PO 4 (1 M) (8 ml). Then the reaction mixture was warmed up to room temperature and water was added, then was extracted with CH 2 Cl 2 (3 x 30 ml), dried (Na 2 SO 4 ) and concentrated. The crude oil was purified through chromatography (silica-gel, hexanes/etoac (7:3). Spectrocopic data for (E)-7-phenylhept-5-en-3-one (yield = 58%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.23-7.44 (5H, m), 5.46-5.81 (2H, m), 3.40 (2H, d, J = 5.0 Hz), 3.15 (2H, m), 2.30-2.57 (2H, m), 0.95-1.24 (3H, t, J = 7.3 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 209.7, 140.3, 133.5, 128.7, 128.6, 128.5, 126.3, 123.8, 46.3, 39.2, 35.5, 7.9 ppm. IR (NaCl) δ, 3084, 3061, 3027, 2976, 2937, 2904, 2841, 1713, 1603, 1495, 1454, 1411, 1355, 1179, 1111, 1030, 970, 919, 747, 699 cm -1. HRMS m/z calcd. for C 13 H 16 ONa [M+Na + ]: 211.1099, found: 211.1096. Spectroscopic data for (E)-6-phenylhex-5-en-3-one (yield = 45%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.19-7.41 (5H, m), 6.43-6.49 (1H, d, J = 16 Hz), 6.28-6.37 (1H, m), 3.31 (2H, dd, J = 1.3, 7.1 Hz), 2.60 (2H, q, J = 7.3 Hz), 1.08 (3H, t, J = 7.3 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 209.5, 137.2, 133.8, 128.8, 127.8, 126.5, 122.5, 46.8, 35.9, 8.0 ppm. IR (NaCl) δ 3082, 3060, 3027, 2977, 2938, 2880, 1714, 1599, 1496, 1450, 1410, 1355, 1201, 1111, 1070, 1029, 967, 915, 746, 694 cm -1. General experimental procedure for the epoxidation of ketones 7 and 8. To an ice-bath cold solution of the alkene (1.03 mmol) in CH 2 Cl 2 (7 ml) were added Na 2 CO 3 (218 mg, 2.06 mmol) followed by meta-chloroperbenzoic acid (85%) (231 mg, 1.03 mmol). The resulting mixture was stirred at room temperature (21 ºC) for 50 min. Then was quenched with saturated aqueous NaHCO 3 solution and extracted with CH 2 Cl 2 (2 x 30 ml). The combined organic layers were dried (Na 2 SO 4 ), filtered and concentrated. The 2 Mattson, M. N.; Rapoport, H. J. Org. Chem. 1996, 61, 6071.

S6 crude oil was purified through chromatography (silica-gel, hexanes/etoac (7:3) to afford the corresponding epoxy ketone as a colorless oil. Spectrocopic data for 1-(3-benzyloxiran-2-yl)butan-2-one 7 (yield = 44%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.19-7.34 (5H, m), 3.14 (1H, dt, J = 2.1, 5.9 Hz), 2.92-2.98 (1H, dq, J = 2.1, 5.5 Hz), 2.90 (2H, t, J = 5.1 Hz), 2.64 (2H, m), 2.41-2.49 (2H, q, J = 7.3 Hz), 1.05 (3H, t, J = 7.3 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 209.0, 134.0, 129.3, 128.85, 128.6, 127.0, 59.0, 54.3, 45.3, 38.5, 36.9, 7.8 ppm. IR (NaCl) δ, 3063, 3028, 2977, 2938, 1712, 1572, 1495, 1455, 1412, 1375, 1288, 1255, 1130, 1071, 1032, 913, 847, 806, 745, 700 cm -1. HRMS m/z calcd. for C 13 H 16 O 2 Na [M+Na + ]: 227.1048, found: 227.1048. Spectroscopic data for 1-(3-phenyloxiran-2-yl)butan-2-one 8 (yield = 51%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.23-7.40 (5H, m), 3.64 (1H, m), 3.26-3.35 (1H, m), 2.72-2.82 (2H, m), 2.54 (2H, q, J = 7.3 Hz), 1.08 (3H, t, J = 7.3 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 208.6, 137.1, 128.8, 128.6, 126.0, 58.6, 58.3, 45.6, 37.0, 7.8 ppm. IR (NaCl) δ, 3063, 3031, 2973, 2939, 2881, 1714, 1575, 1495, 1453, 1286, 1254, 1125, 1027, 752, 700cm -1. HRMS m/z calcd. for C 12 H 14 O 2 Na [M+Na + ]: 213.0081, found: 213.0089. Spectroscopic data for 2-(7-oxabicyclo[4.1.0]heptan-1-yl)cyclohexanone 9. (yield = 51%). 1 H NMR (500 MHz, CDCl 3 ) δ 2.75 (1H, s), 2.06-2.30 (3H, m), 1-71-2.04 (5H, m), 1.49-1.71 (5H, m), 1.18-1.37 (4H, m). 13 C NMR (125 MHz, CDCl 3 ) δ 210.2, 59.6, 59.5, 59.0, 41.9, 28.4, 26.9, 25.3, 24.8, 24.4, 20.0, 18.8 ppm. IR (NaCl) δ, 2935, 2862, 1708, 1448, 1434, 1364, 1308, 1234, 1130, 1071, 1031, 968, 922, 874, 839, 784, 755 cm -1. HRMS m/z calcd. for C 12 H 18 O 2 Na [M+Na + ]: 217.1204, found: 217.1209 OH 30 mol% BF R 1 CO 2 R 3 Et 2 O R O 2 R1 CO 2 R 2 + 1 O 1 R 3 OH, DCM, rt, 18h OR 2 3 3 R 3 O O General experimental procedure for the opening of 3,4-epoxyesters with alcohols. To an ice-bath cold solution of epoxide (0.54 mmol) in a (1/1) mixture of alcohol / CH 2 Cl 2 (2 ml) was added BF 3 OEt 2 (21 μl, 0.16 mmol) dropwise. Then the resulting mixture was stirred at room temperature (21 ºC) for 17 h. Then was quenched with saturated aqueous NaHCO 3 solution and extracted with CH 2 Cl 2 (2 x 30 ml). The combined organic layers were dried (Na 2 SO 4 ), filtered and concentrated. The crude oil was purified through chromatography (silica-gel, hexanes/etoac (7:3) to afford the corresponding compound 2 as a colorless oil. Spectroscopic data for methyl 3-hydroxy-4-methoxypentanoate 2a R 3 = Me (yield = 99%) 1 H NMR (500 MHz, CDCl 3 ) δ 3.93 (dq, J = 4.5, 4.2 Hz, 1H), 3.63 (s, 3H), 3.29 (s, 3H), 3.25 (dq, J = 6.1, 1.3 Hz, 1H), 3.02 (br s, 1H), 2.50 (dd, J = 16.0, 3.8 Hz, 1H), 2.41 (dd, 8.9 Hz, 1H), 1.08 (d, J = 6.3 Hz, 3H). 13 C NMR (125 MHz, CDCl 3 ) δ 173.0, 78.9, 70.4, 56.6, 51.6, 36.9, 14.2 ppm. IR (NaCl) δ 3418, 2975, 2930, 1735, 1439, 1375, 1260, 1216, 1172, 1095, 1027, 800. cm -1. HRMS m/z calcd. for C 7 H 15 O 4 [M+H + ]: 163.0970, found: 163.0967; calcd. for C 7 H 14 O 4 Na [M+Na + ]: 185.0790, found: 185.0790. Spectroscopic data for methyl 3-hydroxy-4-isopropoxypentanoate 2a R 3 = i-pr (yield = 70%). 1 H NMR (500 MHz, CDCl 3 ) δ 3.90 (m, 1H), 3.65 3.71 (m, 4H), 3.47 (m, 1H), 2.57 (dd, J = 3.6, 16.1 Hz, 1H), 2.46 (dd, J = 8.8, 16.1 Hz, 1H), 1.08 1.14 (m, 9H). 13 C NMR (125 MHz, CDCl 3 ) δ 173.5, 74.9, 71.5, 70.1, 52.0, 37.3, 23.5, 22.6, 16.5 ppm. IR (NaCl) δ 3503, 2959, 2925, 2854, 1740, 1458, 1439, 1377, 1260, 1173, 1125, 1075, 1015, 879, 798 cm -1. HRMS m/z calcd. for C 9 H 19 O 4 [M+H + ]: 191.1283, found: 191.1282; calcd. for C 9 H 18 O 4 Na [M+Na + ]: 213.1103, found: 213.1100. Spectroscopic data for methyl 4-tert-butoxy-3-hydroxypentanoate 2a R 3 = t-bu (yield = 77%). 1 H NMR (500 MHz, CDCl 3 ) δ 3.90 (m, 1H), 3.70 (s, 3H), 3.65 (m, 1H), 2.51 (dd, J = 4.3, 15.8 Hz, 1H), 2.46 (dd, J = 8.5, 16.1 Hz, 1H), 1.19 (s, 9H), 1.12 (d, J= 6.2 Hz, 3H). 13 C NMR (125 MHz, CDCl 3 ) δ 173.0, 74.0, 71.7, 69.2, 51.7, 37.0, 28.6, 17.9 ppm. IR (NaCl) δ 3489, 2956, 2925, 2854, 1740, 1458, 1439, 1366, 1259, 1195, 1172, 1073, 849, 800, cm -1. HRMS m/z calcd. for C 10 H 21 O 4 [M+H + ]: 205.1440, found: 205.1438; calcd. for C 10 H 20 O 4 Na [M+Na + ]: 227.1259, found: 227.1255. Spectroscopic data for ethyl 3-hydroxy-4-methoxyhexanoate 2b R 3 = Me (yield = 97%). 1 H NMR (500 MHz, CDCl 3 ) δ 4.14 (2H, q, J = 7.1 Hz), 4.01 (1H, m), 3.38 (3H, s), 3.08 (1H, m), 2.79 (br s, 1H), 2.53 (dd, J = 3.5, 16.2 Hz, 1H), 2.45 (dd, J = 9.0, 16.2 Hz, 1H), 1.61 1.42 (2H, m), 1.24 (3H, t, J= 7.1 Hz), 0.91 (3H, t, J= 7.4 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 173.0, 84.1, 69.0, 60.6, 58.2, 36.9, 22.4, 14.1, 9.4 ppm. IR (NaCl) δ 3464, 2973, 2931, 2878, 1725, 1461, 1374,1256, 1176, 1102, 1031, 984 cm -1. HRMS m/z calcd. for C 9 H 18 O 4 [M+H + ]: 191.1283, found: 191.1278; calcd. for C 9 H 17 O 4 Na [M+Na + ]: 213.1103, found: 213.1102 Spectroscopic data for ethyl 4-ethoxy-3-hydroxyhexanoate 2b R 3 = Et (yield = 98%). 1 H NMR (500 MHz, CDCl 3 ) δ 4.16 (2H, q, J= 7.1 Hz), 4.02 (1H, ddd, J = 3.5, 5.0, 8.8 Hz), 3.54 3.69 (2H, m), 3.20 (1H, dt, J = 4.9, 7.0 Hz), 2.56 (1H, dd, J = 3.5, 16.2 Hz), 2.48 (1H, dd, J = 3.6, 16.2 Hz), 1.47-1.60 (2H, m), 1.54 (2H, m), 1.26 (3H, t, J= 7.2 Hz), 1.18 (3H, t, J= 7.1 Hz), 0.94 (3H, t, J = 7.4

S7 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 173.1, 82.7, 69.3, 65.9, 60.6, 37.0, 22.9, 15.6, 14.1, 9.5 ppm. IR (NaCl) δ 3490, 2972, 2933, 1725, 1575, 1461, 1371, 1287, 1255, 1169, 1095, 1033, 810, 749 cm -1. HRMS m/z calcd. for C 10 H 21 O 4 [M+H + ]: 205.1440, found: 205.1440; calcd. for C 10 H 20 O 4 Na [M+Na + ]: 227.1259, found: 227.1264. Spectroscopic data for ethyl 3-hydroxy-4-isopropoxyhexanoate 2b R 3 = i-pr (yield = 98%). 1 H NMR (500 MHz, CDCl 3 ) δ 4.15 (2H, q, J= 7.2 Hz), 4.01 (1H, ddd, J = 3.9, 4.6, 8.7 Hz), 3.71 (1H, m), 3.29 (1H, dt, J = 4.8, 6.9 Hz), 2.61 (1H, br s), 2.53 (1H, dd, J = 3.8, 16.2 Hz), 2.46 (1H, dd, J = 8.8, 16.2 Hz), 1.43-1.59 (2H, m), 1.25 (3H, t, J= 7.2 Hz), 1.13 (6H, t, J = 6.1 Hz), 0.92 (3H, t, J = 7.4 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 173.0, 79.9, 70.5, 69.4, 60.6, 37.0, 23.0, 22.8, 22.6, 14.1, 9.5 ppm. IR (NaCl) δ 3515, 2972, 2932, 1878, 1736, 1464, 1376, 1177, 1122, 1035 cm -1. HRMS m/z calcd. for C 11 H 23 O 4 [M+H + ]: 219.1596, found: 219.1597; calcd. for C 11 H 22 O 4 Na [M+Na + ]: 241.1416, found: 241.1421 Spectroscopic data for ethyl 4-tert-butoxy-3-hydroxyhexanoate 2b R 3 = t-bu (yield = 99%). 1 H NMR (500 MHz, CDCl 3 ) δ 4.14 (2H, q, J= 7.2 Hz), 4.02 (1H, dt, J= 4.5, 8.3 Hz), 3.48 (1H, dt, J= 4.6, 5.9 Hz), 2.50 (1H, dd, J = 4.5, 16.0 Hz), 2.45 (1H, dd, J = 8.2, 16.0 Hz), 1.55-1.64 (1H, m), 1.43 (1H, tdd, J= 6.1, 7.4, 14.6 Hz), 1.25 (3H, t, J= 7.1 Hz), 1.18 (9H, s), 0.89 (3H, t, J= 7.6 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 172.8, 74.3, 73.9, 69.6, 60.5, 37.2, 28.9, 24.1, 14.2, 9.5 ppm. IR (NaCl) δ 3523, 2976, 2938, 2880, 1784, 1736, 1466, 1390, 1366, 1281, 1254, 1192, 1088, 1071, 1038, 1004, 979, 889, 785 cm -1. HRMS m/z calcd. for C 12 H 25 O 4 [M+H + ]: 233.1753, found: 233.1752; calcd. for C 12 H 24 O 4 Na [M+Na + ]: 255.1572, found: 255.1572. Spectroscopic data for ethyl 4-(benzyloxy)-3-hydroxyhexanoate 2b R 3 = Bn (yield = 96%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.26-7.38 (m, 5H), 4.59 (m, 2H), 4.09-4.21 (m, 3H), 3.38-3.43 (m, 1H), 2.51-2.68 (m, 2H), 1.52-1.72 (2H, m), 1.26 (3H, t, J= 7.2 Hz), 0.98 (3H, t, J= 7.5 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 173.1, 138.5, 128.3, 127.8, 127.6, 82.5, 72.4, 69.4, 60.7, 36.9, 22.8, 14.1, 9.5 ppm. IR (NaCl) δ 3490, 3064, 3032, 2968, 2877, 1731, 1496, 1455, 1374, 1168, 1094, 1028, 737, 697 cm -1. HRMS m/z calcd. for C 15 H 23 O 4 [M+H + ]: 267.1596, found: 267.1591; calcd. for C 15 H 22 O 4 Na [M+Na + ]: 289.1416, found: 289.1414. Spectroscopic data for ethyl 3-hydroxy-4-methoxyheptanoate 2c R 3 = Me (yield = 88%). 1 H NMR (500 MHz, CDCl 3 ) δ 4.13 (2H, q, J = 7.2 Hz), 4.02 (1H, m), 3.38 (3H, s), 3.15 (1H, ddd, J = 4.4, 7.5, 8.6 Hz), 3.01 (1H, d, J = 3.4 Hz), 2.43-2.52 (2H, m), 1.27-1.54 (4H, m), 1.23 (3H, t, J = 7.2 Hz), 0.90 (3H, t, J = 7.1 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 173.0, 83.2, 69.4, 60.6, 58.3, 36.8, 32.0, 18.6, 14.2, 14.1. IR (NaCl) δ 3485, 2959, 2872, 1735, 1464, 1373, 1299, 1175, 1095, 1035, 944, 857, 750 cm -1 HRMS m/z calcd. for C 10 H 20 O 4 Na [M+Na + ]: 227.1259, found: 227.1262 Spectroscopic data for ethyl ethyl 4-(benzyloxy)-3-hydroxyheptanoate 2c R 3 = Bn (yield = 73%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.23-7.36 (5H, m), 4.47-4.72 (2H, m), 4.11 (2H, q, J = 7.3 Hz), 3.45 (1H, m), 3.10 (1H, m), 2.55 (2H, m), 1.30-1.65 (4H, m), 1.23 (3H, t, J = 7.3 Hz), 0.91 (3H, m). 13 C NMR (125 MHz, CDCl 3 ) δ 173.3, 138.8, 128.6, 128.0, 127.8, 81.5, 72.7, 70.1, 60.9, 37.2, 32.7, 18.8, 14.5, 14.4. IR (NaCl) δ 3499, 3097, 3073, 3034, 2968, 2933, 2882, 1788, 1737, 1459, 1178, 1100, 1025, 744, 701 cm -1. HRMS m/z calcd. for C 16 H 24 O 4 Na [M+Na + ]: 303.1572, found: 303.1569 Spectroscopic data for methyl 3-hydroxy-4-methoxy-5-phenylpentanoate 2d R 3 = Me and 5-benzyl-4-methoxydihydrofuran- 2(3H)-one 3d R 3 = Me. (Yield = 79%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.17-7.36 (5H, m) (2d and 3d), 4.68 (1H, td, J = 6.1, 2.4 Hz) (3d), 3.98 (1H, m) (2d), 3.79-3.87 (1H, m) (3d), 3.63-3.74 (3H, s) (2d), 3.36-3-44 (1H, m) (2d), 3.29 (3H, s) (2d), 3.19 (3H, s) (3d), 3.09-3.17 (1H, m) (3d), 2.93-2.99 (1H, m) (3d), 2.78-2.89 (2H, m) (2d), 2.50-2.67 (2H, m) (2d), 2.38-2.46 (1H, m) (3d). 13 C NMR (125 MHz, CDCl 3 ) δ 175.5 (3d), 173.6 (2d), 138.6 (2d), 135.6 (3d), 129.8, 129.0, 128.6, 127.5, 126.5, (2d and 3d), 85.1 (3d), 84.9 (2d), 79.3 (3d), 69.6 (2d), 58.9 (2d), 56.8 (3d), 52.02 (2d), 39.5 (3d), 37.1 (2d), 36.6 (2d), 34.74 (3d). HRMS m/z calcd. for C 13 H 18 O 4 Na [M+Na + ]: 261.1103, found: 261.1100 (2d). HRMS m/z calcd. for C 12 H 15 O 3 Na [M+H + ]: 207.1021, found: 207.1013 (3d). Spectroscopic data for methyl 3-hydroxy-4-methoxy-4-phenylbutanoate 2e R 3 = Me (yield = 95%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.26-7.38 (5H, m), 4.13-4.20 (2H, m), 3.62 (3H, s), 3.30 (3H, s), 2.81 (1H, br s), 2.56 (dd, J = 3.7, 16.1 Hz, 1H), 2.50 (dd, J = 8.5, 16.2 Hz, 1H). 13 C NMR (125 MHz, CDCl 3 ) δ 172.9, 137.9, 128.5, 128.1, 127.4, 85.9, 71.6, 57.2, 51.7, 36.7. IR (NaCl) δ 3482, 3086, 3066, 3033, 2992, 2949, 2825, 1739, 1440, 1356, 1259, 1162, 1108, 968, 763, 703 cm -1 HRMS m/z calcd. for C 12 H 16 O 4 Na [M+Na + ]: 247.0946, found: 247.0949. R 1 CO 2 R 2 O 1 BF 3 Et 2 O R 1 CO 2 R 2 O 4 General experimental procedure for the syntheses of ketoesters 4. To an ice-bath cold solution of epoxide (0.4 mmol) in CHCl 3 (2 ml) was added BF 3 OEt 2 (15 μl, 0.12 mmol) dropwise. Then the resulting mixture was stirred at room temperature (21 ºC) for 17 h. Then was quenched with saturated aqueous NaHCO 3 solution and extracted with CH 2 Cl 2 (2 x 30 ml). The combined organic layers

S8 were dried (Na 2 SO 4 ), filtered and concentrated. The crude oil was purified through chromatography (silica-gel, hexanes/etoac (8:2) to afford the corresponding compound 4 as a colorless oil. Spectroscopic data for methyl 4-oxopentanoate 4a (yield = 90%). 1 H NMR (500 MHz, CDCl 3 ) δ 3.67 (3H, s), 2.74 (2H, t, J = 6.5 Hz), 2.55 (2H, t, J =6.5 Hz), 2.18 (3H, s). 13 C NMR (125 MHz, CDCl 3 ) δ 207.5, 173.7, 52.2, 38.3, 30.2, 28.1 ppm. IR (NaCl) δ 2975, 2938, 2857, 1740, 1454, 1381, 1226, 1167, 1043, 910, 815, 778 cm -1 HRMS m/z calcd. for C 6 H 10 O 3 Na [M+Na + ]: 153.0528, found: 153.0524. Spectroscopic data for ethyl 4-oxohexanoate 4b (yield = 97%). 1 H NMR (500 MHz, CDCl 3 ) δ 4.10 (2H, q, J= 7.1 Hz), 2.69 (2H, t, J = 6.5 Hz), 2.56 (2H, t, J = 6.5 Hz), 2.45 (2H, q, J = 7.2 Hz), 1.23 (3H, t, J = 7.1 Hz), 1.05 (3H, t, J = 7.3 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 209.8, 173.2, 60.9, 36.2, 30.0, 28.4, 14.5, 8.1 ppm. IR (NaCl) δ 2984, 2932, 2905, 2878, 1723, 1459, 1416, 1369, 1025, 986, 920, 857, 803, 732 cm -1 HRMS m/z calcd. for C 8 H 14 O 3 Na [M+Na + ]: 181.0841, found: 181.0835. Spectroscopic data for ethyl 4-oxoheptanoate 4c (yield = 95%). 1 H NMR (500 MHz, CDCl 3 ) δ 4.10 (2H, q, J = 7.1 Hz), 2.69 (2H, t, J = 6.6 Hz), 2.57 (2H, t, J = 6.5 Hz), 2.42 (2H, t, J = 7.3 Hz), 1.61 (2H, m), 1.25 (3H, t, J = 7.1 Hz), 0.91 (3H, t, J = 7.1 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 209.4, 173.2, 60.9, 45.0, 37.4, 28.3, 17.6, 14.5, 14.0 ppm. IR (NaCl) δ 2966, 2935, 2875, 1775, 1735, 1460, 1417, 1373, 1259, 1172, 1035, 944, 860, 740 cm -1. HRMS m/z calcd. for C 9 H 16 O 3 Na [M+Na + ]: 195.0997, found: 195.0996. Bn O 1d CO 2 Et BF 3 Et 2 O 79% Bn O O HO 5 (anti:syn 77:23) anti 5-benzyl-4-hydroxydihydrofuran-2(3H)-one 5. To an ice-bath cold solution of epoxide 1d (110 mg, 0.53 mmol) in CHCl 3 (2 ml) was added BF 3 OEt 2 (33 μl, 0.26 mmol) dropwise. The resulting mixture was stirred at room temperature for 17 h. Then was quenched with saturated aqueous solution of NaHCO 3 and extracted with CH 2 Cl 2 (3 x 30 ml). The combined organic layers were washed with brine, dried (Na 2 SO 4 ), filtered and concentrated. The crude oil was purified through chromatography (silica-gel, hexanes/etoac (1:1) and AcOEt affording lactone 5 as a mixture of diastereomers anti:syn (3.3:1) (80 mg, 79%). 1 H NMR (500 MHz, CDCl 3 ) δ 7.20-7.36 (5H, m), 4.60 (1H, td, J = 6.2, 3.0 Hz), 4.36 (1H, m), 2.98 (2H, m), 2.50 (1H, dd, J = 4.6, 16.2 Hz), 2.44 (1H, dd, J = 5.4, 16.2 Hz), 1.67 (1H, s). 13 C NMR (125 MHz, CDCl 3 ) δ 176.3, 137.4, 129.8, 129.2, 127.6, 87.7, 71.1, 39.3, 37.8 ppm. IR (NaCl) δ 3454, 3080, 3043, 2940, 1772, 1618, 1508, 1368, 1280, 1199, 1059, 927, 832, 751, 714 cm -1. HRMS m/z calcd. for C 11 H 12 O 3 Na [M+Na + ]: 215.0684, found: 215.0682. Et Me BF 3 Et 2 O O CO 2 Et O HO 1f 60% 6 O (R)-5-((S)-1-hydroxypropyl)dihydrofuran-2(3H)-one 6. To an ice-bath cold solution of epoxide 1f (153 mg, 0.89 mmol) in CH 2 Cl 2 (3 ml) was added BF 3 OEt 2 (35 μl, 0.27 mmol) dropwise. Then the resulting mixture was stirred cold with an ice-bath for 3.5 h. Then was quenched with saturated aqueous NaHCO 3 solution and extracted with CH 2 Cl 2 (2 x 30 ml). The combined organic layers were dried (Na 2 SO 4 ), filtered and concentrated. The crude oil was purified through chromatography (silica-gel, hexanes/etoac (1:1)) to afford compound 6 (77 mg, 60%). 1 H NMR (500 MHz, CDCl 3 ) δ 4.41 (1H, m), 3.42-3.52 (1H, m), 2.41-2.66 (2H, m), 2.15-2.27 (1H, m), 2.05-2.15 (1H, m), 1.47-1.65 (2H, m), 0.97 (3H, t, J = 7.5 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 177.9, 83.0, 75.1, 28.9, 26.2, 24.3, 10.2 ppm. IR (NaCl) δ, 3447, 2964, 2879, 1768, 1462, 1417, 1371, 1340, 1190, 923, 812 cm -1. HRMS m/z calcd. for C 7 H 12 O 3 Na [M+Na + ]: 167.0684, found: 167.0680

S9 R O 7, R = Bn 8, R = Ph O Et BF 3 Et 2 O O Et R 10, R = Bn 11, R = Ph O O O BF 3 Et 2 O 9 87% 12 General experimental procedure for the syntheses of furanes 10 and 11. To an ice-bath cold solution of epoxide (0.4 mmol) in CHCl 3 (2 ml) was added BF 3 OEt 2 (15 μl, 0.12 mmol) dropwise. Then the resulting mixture was stirred cold with an ice-bath for 1.5 h. Then was quenched with saturated aqueous NaHCO 3 solution and extracted with CH 2 Cl 2 (2 x 30 ml). The combined organic layers were dried (Na 2 SO 4 ), filtered and concentrated. The crude oil was purified through chromatography (silica-gel, hexanes/etoac (7:3)) to afford the corresponding furan as a yellowish oil. Spectroscopic data for 2-benzyl-5-ethylfuran 10 (yield = 83%) 3. 1 H NMR (300 MHz, CDCl 3 ) δ 7.12-7.41 (5H, m), 5.87 (2H, s), 3.93 (2H, s), 2.61 (2H, q, J = 7.5 Hz), 1.23 (3H, t, J = 7.5 Hz). 13 C NMR (75 MHz, CDCl 3 ) δ 156.7, 152.5, 138.4, 129.1, 128.8, 126.7, 107.0, 104.7, 34.9, 21.7, 12.5 ppm. IR (NaCl) δ, 3061, 3034, 2960, 2924, 2850, 1568, 1498, 1459, 1377, 1264, 1013, 775, 705 cm -1. Spectroscopic data for 2-ethyl-5-phenylfuran 11 (yield = 78%) 4. 1 H NMR (500 MHz, CDCl 3 ) δ 7.57-7.73 (2H, m), 7.31-7.48 (2H, m), 7.11-7.31 (1H, m), 6.58 (1H, d, J = 3.2 Hz), 6.06 (1H, d, J = 3.2 Hz), 2.73 (2H, q, J = 7.6 Hz), 1.27 (3H, t, J = 7.6 Hz). 13 C NMR (125 MHz, CDCl 3 ) δ 157.6, 152.0, 131.5, 128.9, 127.1, 123.7, 106.4, 106.0, 21.9, 12.6 ppm. IR (NaCl) δ, 3083, 3063, 2975, 2929, 2855, 1594, 1548, 1487, 1495, 1377, 1323, 1286, 1209, 1071, 1014, 790, 763, 689 cm -1. Spectroscopic data for 1,2,3,4,6,7,8,9-octahydrodibenzo[β,δ]furan 12. (yield = 87%) 5. 1 H NMR (500 MHz, CDCl 3 ) δ 2.59 (4H, t, J = 6.3 Hz), 2.35 (4H, tt, J = 5.8, 1.6 Hz), 1.80-1.89 (4H, m), 1.70-1.80 (4H, m). 13 C NMR (125 MHz, CDCl 3 ) δ 148.5, 117.0, 23.6, 23.5, 23.4, 21.0 ppm. IR (NaCl) δ, 2928, 2844, 1601, 1443, 1361, 1291, 1263, 1239, 1218, 1170, 1141, 1124, 953, 896, 859, 718 cm -1. 3 Spectra identical to the reported ones: Du, X.; Song, F.; Lu, Y.; Chen, H.; Liu, Y. Tetrahedron 2009, 65, 1839. 4 Spectra identical to the reported ones: Imagawa, H.; Kurisaki, T.; Nishizawa, M. Org. Lett, 2004, 6, 3679. 5 Spectra identical to the reported ones: Hagiwara, H.; Uda, H. J. Chem. Soc. Perkin Trans. I 1984, 91.

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