E. Redero et al. / Tetrahedron 57 +2001) 9597±9605
9601
1H, J12, 4 Hz); 3.35 (m, 2H); 3.68 (dd, 1H, J10, 4 Hz);
4.65 (m, 1H); 7.14 (s, 1H); 7.22 (m, 5H); 13C NMR (CDCl3):
d 19.24 (CH3); 38.41 (CH2); 41.71 (CH2); 67.53 (CH);
76.41 (CH); 88.75 (C); 126.60 (CH); 126.61 (CH); 128.26
(CH); 128.27 (CH); 128.44 (CH); 128.45 (CH); 129.20
(CH); 129.21 (CH); 129.60 (CH); 129.62 (CH); 135.96
(C); 136.94 (C); 137.83 (C); 151.92 (CH); 171.58 (C);
EIMS m/z (relative intensity): 338 (M, 5); 246 (25); 200
(50); 157 (22); 127 (72); 91 (100); 77 (22). Anal. Calcd
for C21H22O4: C, 74.54, H, 6.55; found: C, 74.46, H, 6.49.
J6 Hz); 13C NMR (CD3OD): d 18.78 (CH3); 34.20 (CH2);
55.65 (CH3); 77.20 (CH); 90.50 (C); 110.80 (CH); 121.36
(CH); 121.50 (CH); 126.60 (C); 128.60 (CH); 135.25 (CH);
157.70 (C); 159.80 (CH); 173.22 (C); EIMS m/z (relative
intensity): 249 (M11, 5); 150 (100); 120 (50) 90 (45). Anal.
Calcd for C14H16O4: C, 67.73, H, 6.50; found: C, 67.66, H,
6.42.
4.5.2. ꢀ5Sp,10Rp)-5-[10-Hydroxy-20-ꢀ2-methoxy-phenyl)-
ethyl]-5-methyl-5H-furan-2-one ꢀ31). 19.5%; IR (neat) n
3470, 3150, 1750, 1600, 1495, 1240, 945, 754; H NMR
1
(CDCl3): d 1.55 (s, 3H); 2.90 (m, 2H); 3.75 (m, 1H); 3.84
(s, 3H); 6.06 (d, 1H, J6 Hz); 7.10 (m, 4H); 7.54 (d, 1H,
J6 Hz); 13C NMR (CDCl3): d 18.88 (CH3); 33.86 (CH2);
55.67 (CH3); 76.61 (CH); 90.66 (C); 110.73 (CH); 121.12
(CH); 121.39 (CH); 126.41 (C); 128.55 (CH); 131.60 (CH);
157.45 (C); 159.80 (CH); 172.81 (C); EIMS m/z (relative
intensity): 249 (M11, 15); 150 (100); 120 (60); 98 (35); 90
(40). Anal. Calcd for C14H16O4: C, 67.73, H, 6.50; found: C,
67.68, H, 6.40.
4.4. Reaction with 2-bromo-phenylacetaldehyde
p
4.4.1. ꢀ5S0 ,10Sp)-5-[20-ꢀ2-Bromophenyl)-10-hydroxy-ethyl]-
5-methyl-5H-furan-2-one ꢀ26). 0.3%; IR (neat) n 3425,
1
2950, 1750, 1470, 1442, 1260, 1110, 1080, 1030, 740; H
NMR (CDCl3): d 1.59 (s, 3H); 2.75 (m, 1H); 3.22 (m, 1H);
3.12 (m, 1H); 3.95 (m, 1H); 6.12 (d, 1H, J6 Hz); 7.20 (m,
4H); 7.52 (d, 1H, J6 Hz); 13C NMR (CDCl3): d 18.62
(CH3); 41.85 (CH2); 79.70 (CH); 90.50 (C); 120.93 (CH);
127.38 (CH); 127.51 (CH); 126.61 (CH); 128.26 (CH);
137.06 (C); 158.20 (C); 173.22 (C); EIMS m/z (relative
intensity): 298 (M11, 5); 201 (25); 169 (20); 149 (25); 98
(100); 91 (50); 77 (100). Anal. Calcd for C13H13BrO3: C,
52.55, H, 4.41; found: C, 52.46, H, 4.32.
4.5.3. 3,5-Bis-[10-hydroxy-20-ꢀmethoxy-phenyl)-ethyl]-5-
methyl-5H-furan-2-one ꢀ33). 45%; IR (neat) n 3440,
1
1750, 1474, 1440, 1265, 1028; H NMR (CDCl3): d 1.60
(s, 3H); 2.60 (m, 1H); 3.15 (m, 1H); 3.30 (m, 2H); 3.95 (m,
1H); 4.95 (m, 1H); 7.20 (m, 8H); 7.25 (s, 1H); 13C NMR
(CD3OD): d 19.56 (CH3); 38.56 (CH2); 41.68 (CH); 55.60
(CH3); 66.35 (CH); 74.50 (CH); 89.00 (C); 125.40 (C);
126.50 (C); 127.34 (CH); 128.37 (CH); 128.42 (CH);
128.60 (CH); 132.00 (CH); 132.03 (CH); 132.72 (CH);
132.75 (CH); 151.20 (CH); 157.35 (C); 157.60 (C);
171.50 (C). Anal. Calcd for C23H26O6: C, 69.33, H, 6.58;
found: C, 69.26, H, 6.47.
p
4.4.2. ꢀ5S0 ,10Rp)-5-[20-ꢀ2-Bromophenyl)-10-hydroxy-ethyl]-
5-methyl-5H-furan-2-one ꢀ27). 14.7%; IR (neat) n 3420,
2950, 1751, 1474, 1443, 1265, 1109, 1080, 1028, 822, 739;
1H NMR (CDCl3): d 1.59 (s, 3H); 2.75 (dd, 1H, J10,
12 Hz); 3.17 (dd, 1H, J12, 3 Hz); 3.90 (dd, 1H, J10,
3 Hz); 6.12 (d, 1H, J6 Hz); 7.20 (m, 3H); 7.52 (d, 2H,
J6 Hz) ppm; 13C NMR (CDCl3): d 19.73 (CH3); 38.66
(CH2); 74.56 (CH); 90.47 (C); 121.61 (CH); 127.53 (CH);
128.58 (CH); 131.98 (CH); 132.96 (CH); 137.06 (C);
158.20 (CH); 172.10 (C); EIMS m/z (relative intensity):
298 (M11, 5); 199 (10); 171 (16); 153 (32); 98 (70); 77
(100). Anal. Calcd for C13H13BrO3: C, 52.55, H, 4.41;
found: C, 52.48, H, 4.37.
4.6. Lewis acid-promoted aldol condensation of
silyloxyfuran ꢀ4) with aldehydes
A 0.5 M solution of the aldehyde (1 equiv.) and 2-(tert-
butyldimethylsilyloxy)-5-methyl furan 4 (1 equiv.) in dry
CH2Cl2 was cooled at 2788C under argon. Then, the
Lewis acid (1 equiv.) was added dropwise and the reaction
mixture was stirred for 6 h at the same temperature. The
reaction was then quenched by the addition of an aq.
NaHCO3 solution and after ambient temperature had been
reached, the mixture was extracted with CH2Cl2 and the
organic layer was washed with brine, dried (Na2SO4) and
concentrated in vacuo. The residue was ¯ash-chromato-
graphed on silica gel. Elution with hexane±ethyl acetate
(7:3) led to the isolation of the following products.
4.4.3. 3,5-Bis-[20-ꢀ2-bromo-phenyl)-10-hydroxy-ethyl]-5-
methyl-5H-furan-2-one ꢀ29). 47%; IR (neat) n 3441,
1
1751, 1474, 1441, 1265, 1028, 739; H NMR (CDCl3): d
1.57 (s, 3H); 2.55 (dd, 1H, J12, 10 Hz); 3.10 (dd, 1H,
J12, 3 Hz); 3.28 (m, 1H); 3.90 (dd, 1H, J10, 3 Hz);
4.90 (m, 1H); 7.20 (m, 6H); 7.23 (s, 1H); 7.54 (d, 2H,
J7 Hz); 13C NMR (CDCl3): d 19.58 (CH3); 38.58 (CH2);
41.67 (CH); 66.33 (CH); 74.44 (CH); 89.03 (C); 124.47 (C);
125.00 (C); 127.23 (CH); 127.34 (CH); 128.37 (CH);
128.39 (CH); 132.00 (CH); 132.03 (CH); 132.72 (CH);
132.75 (CH); 136.40 (C); 136.46 (C); 137.12 (C); 151.18
(CH); 171.50 (C); EIMS m/z (relative intensity): 497 (M11,
10); 324 (10); 279 (8); 199 (30); 171 (50); 127 (100). Anal.
Calcd for C21H20Br2O4: C, 50.83, H, 4.06; found: C, 50.76,
H, 3.98.
4.7. Reaction with benzaldehyde
4.7.1. 3-ꢀ10-Hydroxy-phenylmethyl)-5-methyl-3H-furan-
2-one ꢀ11). 51% as a mixture of diastereoisomers. The
following spectroscopic properties for the major isomer
1
are given: IR (neat) n 3479, 1735, 1112, 968, 726; H
4.5. Reaction with 2-methoxy-phenylacetaldehyde
NMR (CDCl3): d 1.98 (s, 3H); 3.50 (m, 1H); 4.94 (m,
1H); 5.25 (m, 1H); 7.35 (m, 5H); 13C NMR (CDCl3): d
22.40 (CH3); 54.06 (CH); 72.36 (CH); 103.21 (CH);
127.30 (CH); 127.35 (CH); 127.40 (CH); 128.70 (CH);
128.72 (CH); 140.90 (C); 142.95 (C); 168.0 (C). Anal.
Calcd for C12H12O3: C, 70.58, H, 5.92; found: C, 70.49,
H, 5.87. (9): (15.7%) and (10): (0.3%).
4.5.1. ꢀ5Sp,10Sp)-5-[10-Hydroxy-20-ꢀ2-methoxy-phenyl)-
ethyl]-5-methyl-5H-furan-2-one ꢀ30). 0.5%; IR (neat) n
3470, 2935, 1750, 1028, 740; H NMR (CDCl3): d 1.57
1
(s, 3H); 2.85 (m, 1H); 3.05 (m, 1H); 3.85 (m, 1H); 3.86
(s, 3H); 6.10 (d, 1H, J6 Hz); 7.20 (m, 4H); 7.58 (d, 1H,