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16 Experimental Procedure for Aldol Reactions:
CF3SO3H (1.2 equiv) was added to BEt3 (1
M in hexanes, 1.2 equiv) at r.t. then warmed to 40 °C for
10 minutes before cooling to 0 °C and subsequent addition
via cannula to a solution of N-acyl-oxazolidin-2-one
(1 equiv) in CH2Cl2. After 10 minutes, i-Pr2NEt (1.4 equiv) was added
and the reaction mixture stirred for a further 20 minutes before
cooling to -78 °C and the addition of freshly
distilled aldehyde (1.1 equiv). After 30 minutes the reaction mixture
was warmed to 0 °C and stirred for a further hour before
the addition of MeOH-H2O2 (v/v,
1:1). The reaction mixture was extracted with CH2Cl2, washed
with brine, dried and concentrated in vacuo before purification
by flash column chromatography.
17 Experimental Procedure for DIBALH
Reduction: DIBALH (1 M in hexanes, 2 equiv) was added to a stirred
solution of N-acyl-oxazolidin-2-one (1
equiv) in anhydrous CH2Cl2 at
-78 °C.
After 30 minutes, the reaction mixture was quenched with saturated
aqueous NH4Cl solution and stirred for a further 20 minutes.
The resultant emulsion was filtered through Celite®, dried
and concentrated in vacuo before purification by flash column chromatography.
18
1H NMR data for
tetrose 8; δH (400
MHz, CDCl3) 0.01, 0.04 [2 × 3 H, s,
Si(CH3)2
t-Bu],
0.86 [9 H, s, SiC(CH
3
)3], 3.53 [1 H,
dd, J = 9.8 Hz, 4.9, C(4)H
A
],
3.61 [1 H, dd, J = 9.8
Hz, 5.6, C(4)H
B
],
3.88 [1 H, dd, J = 4.5
Hz, 1.3, C(2)H], 4.16-4.19 [1
H, m, C(3)H], 4.48 [2
H, ABq, J = 12.2 Hz, OCH
2
Ph],
4.57 [1 H, AB, J = 12.0
Hz, C(2)OCH
A
HBPh], 4.77 [1
H, AB, J = 12.0 Hz, C(2)OCH
A
H
BPh],
7.27-7.37 (10 H, m, PhH), 9.76
(1 H, d, J = 1.3 Hz, CHO).
19a
Smith AB.
Ott GR.
J. Am. Chem. Soc.
1996,
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13095
19b
Smith AB.
Chen SS.-Y.
Nelson FC.
Reichert RC.
Salvatore BA.
J.
Am. Chem. Soc.
1995,
117:
12017
20
1H NMR data for
lactone 10; δH (400
MHz, CDCl3) 2.56 (1 H, d, J = 2.3
Hz, OH), 3.68-3.76 [2
H, m, C(6)H
2
OBn], 4.08-4.11 [1
H, m, C(3)H], 4.17 [1
H, t, J = 2.3 Hz, C(4)H], 4.32 [1 H, d, J = 9.7 Hz, C(2)H], 4.43-4.47 [1
H, m, C(5)H], 4.52 [2
H, ABq, J = 11.7 Hz, C(6)H2OCH
2
Ph],
4.62 [1 H, d, J = 11.2
Hz, C(4)OCH
A
HBPh],
4.72 [1 H, d, J = 11.2
Hz, C(2)OCH
A
HBPh],
4.85 [1 H, d, J = 11.2
Hz, C(4)OCHA
H
B
Ph], 5.19 [1
H, d, J = 11.2 Hz, C(2)OCHA
H
B
Ph],
7.21-7.43 (15 H, m, PhH).
21 Commercially available from the Aldrich
Chemical company.