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S. Hirasawa et al. / Tetrahedron 63 (2007) 10930–10938
phenyl ester 1g (208 mg, 77%) as an oil. IR (neat) 3031,
2926, 2856, 1733, 1634, 1592, 1495, 1455, 1326, 1200,
167.2, 141.7, 138.7, 134.3, 132.2, 128.95, 128.87, 127.9,
127.8, 125.7, 121.3, 57.9, 34.3; MS m/z 277 (M+, 11%),
172 (100), 105 (74), 77 (41); HRMS calcd for C18H15NO2
(M+) 277.1103, found 277.1088.
1
1163, 1069, 1028, 948, 914, 859, 809, 746, 690 cmꢀ1; H
NMR (400 MHz) d 7.39–7.04 (10H, m, Phꢂ2), 6.45 (1H,
d, J¼1.6 Hz, ]CHH), 5.82 (1H, d, J¼1.6 Hz, ]CHH),
4.56 (1H, d, J¼11.6 Hz, OCHHPh), 4.53 (1H, d,
J¼11.6 Hz, OCHHPh), 3.65 (1H, m, CHOBn), 2.69 (1H,
dd, J¼14.0, 6.8 Hz, CHH), 2.61 (1H, dd, J¼14.0, 5.2 Hz,
CHH), 1.63–1.18 (12H, m, (CH2)6), 0.88 (3H, t, J¼6.8 Hz,
CH3); 13C NMR (100 MHz) d 165.6, 150.7, 138.6,
137.1, 129.3, 128.9, 128.2, 127.8, 127.4, 125.7, 121.5,
77.7, 71.2, 37.3, 34.1, 31.9, 29.7, 29.3, 25.4, 22.7, 14.2;
MS m/z 287 (M+ꢀOPh, 20%), 219 (10), 159 (21), 91
(100); HRMS calcd for C19H27O2 (M+ꢀOPh) 287.2011,
found 287.2010.
4.3. Conjugate reduction
General procedure: to a solution of a,b-unsaturated ester in
dry dichloromethane (0.1 mol dmꢀ3) was added MgBr2$
OEt2 (3 equiv) under N2 atmosphere. After being stirred at
room temperature for 15 min, the reaction mixture was
cooled to 0 ꢁC, and Bu3SnH (2 equiv) was added. The mix-
ture was stirred at 0 ꢁC for 5 h. Then KF and water were
added and the mixture was stirred at room temperature for
3 h. After filtration through a pad of Florisil, the solvent
was evaporated in vacuo. The residue was purified by col-
umn chromatography on silica gel to afford corresponding
reduction product.
4.2.7. 4,4-Dimethyl-2-oxotetrahydrofuran-3-yl 2-phen-
ethylpropenoate (4c). To a solution of pantolactone
(346 mg, 2.7 mmol) in dry dichloromethane (10 cm3) were
added 4-(dimethylamino)pyridine (29 mg) and 2-phenethyl-
propenoic acid (417 mg, 2.4 mmol), obtained by hydrolyzing
ethyl phenethylpropenoate6g as described for the preparation
of 19. The mixturewas cooled to 0 ꢁC and N,N0-dicyclohexyl-
carbodiimide (580 mg, 2.8 mmol) was added. The mixture
was stirred at room temperature for 16 h. Ethyl acetate was
added and the resulting precipitate of N,N0-dicyclohexylurea
was eliminated by filtration and the filtrate was dried over
anhydrous sodium sulfate and evaporated in vacuo. The res-
idue was purified by column chromatography on silica gel to
give 4c (394 mg, 58%) as a colorless solid. Mp 49.5–50.5 ꢁC
(from hexane); IR (KBr) 1799, 1717, 1634, 1456, 1308,
4.3.1. Phenyl 2-methyl-4-phenylbutanoate (2d). IR (neat)
2978, 2934, 2851, 1757, 1593, 1493, 1457, 1382, 1195,
1159, 1137, 1110, 915, 748, 689 cmꢀ1
;
1H NMR
(400 MHz) d 7.38–7.06 (10H, m, Phꢂ2), 2.73 (3H, m,
CH2Ph, CHCO2Ph), 2.16 (1H, m, CHHCH2Ph), 1.86 (1H,
m, CHHCH2Ph), 1.34 (3H, d, J¼7.1 Hz, CH3); 13C NMR
(100 MHz) d 174.8, 150.6, 141.3, 129.3, 128.4, 128.3,
125.9, 125.6, 121.4, 39.2, 35.4, 33.5, 17.2; MS m/z 161
(M+ꢀOPh, 51%), 133 (14), 91 (100); HRMS calcd for
C11H13O (M+ꢀOPh) 161.0966, found 161.0938.
1
4.3.2. Phenyl (E)-2-methyl-3-phenylpropenoate (7). H
1
1251, 1137, 1079, 1009, 957, 754, 703 cmꢀ1; H NMR
NMR (400 MHz) d 7.93 (1H, s, ]CH), 7.49–7.15 (10H,
m, Phꢂ2), 2.24 (3H, d, J¼1.0 Hz, CH3); 13C NMR
(100 MHz) d 167.1, 151.0, 140.5, 135.5, 129.7, 129.3,
128.6, 128.4, 127.7, 125.6, 121.6, 14.3; MS m/z 238 (M+,
4%), 145 (100), 117 (80), 115 (54); HRMS calcd for
C16H14O2 (M+) 238.0994, found 238.1019.
(400 MHz) d 7.32–7.16 (5H, m, Ph), 6.29 (1H, s, ]CHH),
5.64 (1H, s, ]CHH), 5.46 (1H, s, COOCH), 4.08 (1H, d,
J¼9.3 Hz, CHHO), 4.06 (1H, d, J¼9.3 Hz, CHHO), 2.83
(2H, t, J¼7.8 Hz, PhCH2), 2.67 (2H, t, J¼7.8 Hz, CH2),
1.24 (3H, s, CH3), 1.15 (3H, s, CH3); 13C NMR
(100 MHz) d 172.2, 165.5, 141.0, 138.5, 128.4, 128.3,
127.4, 126.0, 76.2, 75.2, 40.4, 34.8, 33.9, 23.1, 20.1; MS
m/z 288 (M+, 2%), 158 (84), 91 (100); HRMS calcd for
C17H20O4 (M+) 288.1362, found 288.1390.
4.3.3. Phenyl syn-4-benzyloxy-2-methylundecanoate
(syn-2g). IR (neat) 3037, 2926, 2855, 1757, 1593, 1493,
1455, 1382, 1352, 1200, 1159, 1119, 1068, 745, 690 cmꢀ1
;
1H NMR (400 MHz) d 7.37–6.96 (10H, m, Phꢂ2), 4.55
(1H, d, J¼11.6 Hz, OCHHPh), 4.47 (1H, d, J¼11.6 Hz,
OCHHPh), 3.53 (1H, m, CHOBn), 3.00 (1H, m, CHHCHO-
Bn), 2.04 (1H, m, CHHCHOBn), 1.55–1.27 (12H, m,
(CH2)6), 1.33 (3H, d, J¼6.8 Hz, CH3), 0.88 (3H, t,
J¼6.0 Hz, CH3); 13C NMR (100 MHz) d 175.1, 150.7,
138.6, 129.2, 128.3, 128.0, 127.5, 125.5, 121.5, 77.2, 71.3,
39.6, 36.2, 33.9, 31.9, 29.8, 29.3, 25.2, 22.7, 18.3, 14.2;
MS m/z 289 (M+ꢀOPh, 92%), 184 (59), 150 (52), 91 (100);
HRMS calcd for C19H29O2 (M+ꢀOPh) 289.2168, found
289.2185.
4.2.8. 4,4-Dimethyl-2-oxotetrahydrofuran-3-yl 2-methyl-
2-butenoate (4e). Using the procedure as described above,
pantolactone (853 mg, 6.6 mmol) was esterified with (E)-
2-methyl-2-butenoic acid (598 mg, 6.0 mmol) to give 4e
(982 mg, 77%) as a colorless oil. IR (neat) 1791, 1723,
1
1653, 1249, 1132, 1096, 794 cmꢀ1; H NMR (400 MHz)
d 7.01 (1H, qq, J¼6.8, 1.4 Hz, ]CH), 5.45 (1H, s, COOCH),
4.07 (1H, d, J¼8.8 Hz, CHHO), 4.06 (1H, d, J¼8.8 Hz,
CHHO), 1.89 (3H, br s, ]CCH3), 1.84 (3H, dq, J¼6.8,
1.4 Hz, ]CCH3), 1.22 (3H, s, CH3), 1.14 (3H, s, CH3);
MS m/z 212 (M+, 7%), 83 (100), 82 (95); HRMS calcd for
C11H16O4 (M+) 212.1049, found 212.1013.
4.3.4. Phenyl 4-benzyloxy-2-methyl-4-phenylbutanoate
(2h). IR (neat) 3063, 3030, 2970, 2871, 1755, 1593, 1495,
1455, 1381, 1195, 1167, 1107, 1067, 1027, 915, 747,
691 cmꢀ1; MS m/z 267 (M+ꢀOPh, 93%), 189 (21), 184
(29), 175 (19), 131 (18), 105 (16), 91 (100); HRMS calcd
for C18H19O2 (M+ꢀOPh) 267.1385, found 267.1364.
4.2.9. 1-Benzoyl-3-methylene-5-phenylpyrrolidin-2-one
(12). Mp 161.0–161.4 ꢁC (from diethyl ether–hexane); IR
(KBr) 1722, 1683, 1652, 1294, 1254, 1202, 1160, 1017,
954, 866, 812, 746, 699 cmꢀ1 1H NMR (400 MHz)
;
d 7.66–7.26 (10H, m, Phꢂ2), 6.27 (1H, t, J¼2.4 Hz,
]CHH), 5.59 (1H, t, J¼2.4 Hz, ]CHH), 5.48 (1H, dd,
J¼8.7, 4.8 Hz, CHPh), 3.34 (1H, ddt, J¼17.0, 8.7, 2.4 Hz,
CHH), 2.81 (1H, m, CHH); 13C NMR (100 MHz) d 170.9,
1
syn-2h: H NMR (400 MHz) d 7.39–6.95 (15H, m, Phꢂ3),
4.51 (1H, dd, J¼9.6, 3.6 Hz, CHOBn), 4.46 (1H, d,
J¼11.6 Hz, OCHHPh), 4.27 (1H, d, J¼11.6 Hz, OCHHPh),