696 J . Org. Chem., Vol. 63, No. 3, 1998
Kagoshima et al.
Sch em e 6
over MgSO4 and concentrated under reduced pressure. The
residue was purified by column chromatography (hexane/CH2-
Cl2 ) 3/2) to give the less-polar isomer (2.51 g, 34%) and the
more-polar isomer (4.53 g, 61%), respectively, as colorless
crystals.
Hz), 4.13 (dq, 1H, J ) 3.6 and 6.9 Hz), 3.05 (d, 1H, J ) 2.6
Hz), 1.12 (d, 3H, J ) 6.9 Hz); IR (KBr) 3480, 1775, 1675 cm-1
;
MS (EI, 70 eV) m/z 325 (M+), 219 (M+ - PhCHO). Anal. Calcd
for C19H19NO4: C, 70.14; H, 5.88; N, 4.30. Found: C, 70.02;
H, 6.05; N, 4.43.
An aliquot of the less-polar isomer was recrystallized from
hexane/AcOEt (5/1) to give an analytical sample. Colorless
(4R,5S)-3-[(2R,3R)-3-H yd r oxy-2-m et h yl-3-p h en ylp r o-
p ion yl]-4,5-d ip h en yl-2-oxa zolid in on e (10j). Column chro-
matography (CH2Cl2) of the crude product gave a mixture of
diastereomers 10-12j (94% based on the amount of 1a ) and
4j (22% based on the amount of 2j). The diastereomer ratio
was determined by GC analysis (column temperature; 250 °C)
of the trimethylsilylated adducts (syn:anti ) 99:1, 10j:11j )
99:1) (10j, 40.6 min; 11j, 47.4 min; anti isomers, 39.8 and 52.7
min). Recrystallization (hexane/AcOEt ) 3/1) of the diaste-
crystals: mp 127 °C; [R]19 +10.9 (c 1.02, CHCl3); 1H NMR
D
(CDCl3) δ 7.2-6.8 (m, 10H), 5.99 (d, 1H, J ) 7.6 Hz), 5.84 (q,
1H, J ) 6.8 Hz), 5.66 (d, 1H, J ) 7.6 Hz), 1.81 (d, 3H, J ) 6.8
Hz); IR (KBr) 1785, 1705 cm-1; MS (EI, 70 eV) m/z 375, 373.
Anal. Calcd for C18H16NBrO3: C, 57.77; H, 4.31; N, 3.74.
Found: C, 57.77; H, 4.28; N, 3.69.
An aliquot of the more-polar isomer was recrystallized from
hexane/AcOEt (3/1) to give an analytical sample. Colorless
reomer mixture gave 10j in 83% recovery. Colorless crystals:
crystals: mp 123 °C; [R]19 +28.6 (c 1.01, CHCl3); 1H NMR
mp 155 °C; [R]19 +45.3 (c 1.03, CHCl3); H NMR (CDCl3) δ
1
D
D
(CDCl3) δ 7.2-6.9 (m, 10H), 5.92 (d, 1H, J ) 7.9 Hz), 5.79 (q,
1H, J ) 6.6 Hz), 5.72 (d, 1H, J ) 7.9 Hz), 1.84 (d, 3H, J ) 6.6
Hz); IR (KBr) 1800, 1720 cm-1; MS (EI, 70 eV) m/z 375, 373.
Anal. Calcd for C18H16NBrO3: C, 57.77; H, 4.31; N, 3.74.
Found: C, 57.52; H, 4.26; N, 3.69.
7.5-6.8 (m, 15H), 5.74 (d, 1H, J ) 7.6 Hz), 5.58 (d, 1H, J )
7.6 Hz), 5.12 (dd, 1H, J ) 2.6 and 4.0 Hz), 4.20 (dq, 1H, J )
4.0 and 6.9 Hz), 3.04 (d, 1H, J ) 2.6 Hz), 1.22 (d, 3H, J ) 6.9
Hz); IR (KBr) 3500, 1780, 1705 cm-1; MS (EI, 70 eV) m/z 401
(M+), 295 (M+ - PhCHO). Anal. Calcd for C25H23NO4: C,
74.80; H, 5.77; N, 3.49. Found: C, 74.62; H, 5.87; N, 3.48.
(4R,5S)-3-[(2R,3S)-3-H yd r oxy-2-m et h ylh exa n oyl]-4,5-
d ip h en yl-2-oxa zolid in on e (10k ). Column chromatography
(CH2Cl2) of the crude product gave a mixture of diastereomers
10-12k (86% based on the amount of 1b) and 4j (25% based
on the amount of 2j). The diastereomer ratio was determined
by GC analysis (column temperature; 100 °C to 250 °C at 10
°C/min) of the trimethylsilylated adducts (syn:anti ) 97:3, 10k :
11k ) 99:1) (10k , 31.8 min; 11k , 33.7 min; anti isomers, 30.2
and 32.9 min). Recrystallization (hexane/AcOEt ) 10/1) of the
diastereomer mixture gave 10k in 70% recovery. Colorless
Gen er a l P r oced u r e for th e Asym m etr ic Refor m a tsk y
8
Rea ction . To a yellow suspension of GeI2 (718 mg, 2.20
mmol), which had been predried at 100 °C for 1 h under
reduced pressure, in THF (4 mL) was added freshly cut
potassium metal (156 mg, 4.00 mmol), and the mixture was
vigorously stirred for 2 h under reflux. The resulting black
suspension was allowed to cool to room temperature. To this
suspension of activated germanium metal in THF were suc-
cessively added dropwise 2 (2.00 mmol) in THF (4 mL) and
the aldehyde (1.00 mmol) in THF (2 mL). The resulting
mixture was stirred under the conditions listed in Table 5. The
reaction was quenched with water (2 mL), and the volatiles
were evaporated. The resultant suspension in water was
filtered through a small pad of Celite and washed with CH2-
Cl2 (3 × 5 mL). The organic layer was separated, and the
aqueous layer was extracted with CH2Cl2 (3 × 10 mL). The
combined organic layers were dried over MgSO4 and concen-
trated under reduced pressure to give the corresponding crude
product.
crystals: mp 113-114 °C; [R]17 +35.6 (c 1.04, CHCl3); 1H
D
NMR (CDCl3) δ 7.2-6.8 (m, 10H), 5.92 (d, 1H, J ) 7.6 Hz),
5.69 (d, 1H, J ) 7.6 Hz), 4.00 (m, 1H), 3.86 (dq, 1H, J ) 2.6
and 6.9 Hz), 2.81 (d, 1H, J ) 3.0 Hz), 1.6-1.3 (m, 4H), 1.25
(d, 3H, J ) 6.9 Hz), 0.96 (t, 3H, J ) 6.9 Hz); IR (KBr) 3450,
1790, 1685 cm-1; MS (EI, 70 eV) m/z 349 (M+ - 18). Anal.
Calcd for C22H25NO4: C, 71.91; H, 6.86; N, 3.81. Found: C,
72.12; H, 6.91; N, 3.97.
(4R)-3-[(2R,3R)-3-Hydr oxy-2-m eth yl-3-ph en ylpr opion yl]-
4-p h en yl-2-oxa zolid in on e (10g). Column chromatography
(CH2Cl2) of the crude product gave a mixture of diastereomers
10-12g (91% based on the amount of 1a ) and 4g (19% based
on the amount of 2g). The diastereomer ratio was determined
by GC analysis (column temperature; 230 °C) of the trimeth-
ylsilylated adducts (syn:anti ) 97:3, 10g:11g ) 98:2) (10g, 23.9
min; 11g, 26.2 min; anti isomers, 23.6 and 29.0 min). Recrys-
tallization (hexane/AcOEt ) 3/1) of the diastereomer mixture
(4R,5S)-3-[(2R,3S)-3-Hyd r oxy-2,4-d im eth ylp en ta n oyl]-
4,5-d ip h en yl-2-oxa zolid in on e (10l). Column chromatogra-
phy (CH2Cl2) of the crude product gave a mixture of diaster-
eomers 10-12l (79% based on the amount of 1c) and 4j (22%
based on the amount of 2j). The diastereomer ratio was
determined on the basis of 1H NMR integration of the hydroxy
group protons (syn:anti ) 95:5, 10l:11l ) 97:3) [10l, δ 2.84 (d,
J ) 3.3 Hz); 11l, δ 2.45 (d, J ) 3.3 Hz); anti isomers, δ 2.60
(d, J ) 9.6 Hz) and 2.50 (d, J ) 7.9 Hz)]. Recrystallization
(hexane/ether ) 10/1) of the diastereomer mixture gave 10l
gave 10g in 80% recovery. Colorless crystals: mp 119-120
1
°C; [R]19 -47.9 (c 1.04, CHCl3); H NMR (CDCl3) δ 7.5-7.2
in 65% recovery. Colorless crystals: mp 137 °C; [R]19 +46.8
D
D
(m, 10H), 5.36 (dd, 1H, J ) 3.6 and 8.9 Hz), 5.08 (t, 1H, J )
3.1 Hz), 4.57 (t, 1H, J ) 8.9 Hz), 4.21 (dd, 1H, J ) 3.6 and 8.9
(c 1.00, CHCl3); 1H NMR (CDCl3) δ 7.2-6.8 (m, 10H), 5.92 (d,
1H, J ) 7.8 Hz), 5.69 (d, 1H, J ) 7.8 Hz), 4.07 (dq, 1H, J )