May 1998
SYNLETT
521
+
(
50mL). A fine white precipitate formed which was filtered
[α]23 = +21.3 (c 0.8, CHCl ); (Found MH 158.1187. C H15NO2
D
3
8
+
through Celite and washed with ethyl acetate (2x100mL). The
combined filtrates were evaporated, redissolved in ether (100mL),
filtered through Celite and evaporated again to provide the
dimethyl alcohol 7 as an oil (13.84g, 87%); [α] D= -6.0 (c 1.0,
CHCl ); (Found: MH 232.1913. C12H25NO requires MH+
2
(
1
(
CH C), 0.89 (6H, m, CH(CH ) ); δ (50MHz; CDCl ) 157.2
(
(
(
1
(
requires MH 158.1181); υ
(KBr) 1732 (C=O); δH (500MHz;
CDCl ) 6.30 (1H, s (br), NH), 3.19 (1H, d, J 8.7, CHNH), 1.80-
max
3
1.87 (1H, m, CH CH), 1.48 (3H, s, CH C), 1.39 (3H, s, CH C),
3
3
3
2
3
1.00 (3H, d, J 6.6, CH CH), 0.92 (3H, d, J 6.6, CH )CH); δ
3 3 C
+
3
3
(50MHz; CDCl ) 155.9 (C=O), 83.9 (OC(CH ) ), 68.5 (CHNH),
3 3 3
32.1913);.υmax (Film)/cm-1 3446 (OH), 1694 (C=O); δH
28.4 (CH CH), 28.3 (CH C), 21.1 (CH C), 20.9 (CH CH) 19.8
3
3
3
3
200MHz, CDCl ) 4.88 (1H, d (br), J 10.4, NHCH), 3.35 (1H, dd,J
+
+
+
3
(CH CH); m/z (CI ) 315 (M H , 20%), 271 (5), 158 (MH , 70),
3
2
0.4, J 2.4, NHCH), 2.07-2.17 (1H, m, CH(CH ) ), 2.04 (1H, s
3 2
br), OH), 1.42 (9H, s, 3xCH ), 1.23 (3H, s, CH C), 1.19 (3H, s,
3 3
128 (5), 114 (100).
(RS)-N-(t-butylcarboxy)-3-amino-4-methylpentan-2-one 12
3
3 2
C
3
Ketone 13 was separated from the crude reaction for the
C=O), 78.9 (OC(CH ) ), 73.6 (COH), 61.7 (CHNH), 28.8
3 3
preparation of the valine dimethyl alcohol 7 by column
CH CH), 28.2 (3xCH ), 28.1 (CH C), 26.9 (CH C), 22.2
3 3 3 3
chromatography (1:5 ether / petrol) (341mg, 1.59mmol, 2%) as
colourless needles; m.p. 71-74°C; [α]23D= +0.4 (c 1.0, CHCl3);
+
+
CH CH), 16.8 (CH CH); m/z (CI ) 232 (MH , 10%), 176 (42),
3 3
58 (76), 132 (100), 114 (68).
S)-4-i-Propyl-5,5-dimethyloxazolidin-2-one 8
(
Found: C, 61.05; H, 9.80; N, 6.1. C11H21NO requires C, 61.4;
3
H, 9.8; N, 6.5%); υmax (KBr)/cm-1 3292 (NH), 1736 (C=O), 1678
N-CO); δH (200MHz; CDCl ) 5.13 (1H, m, NH), 4.31 (1H, m,
Potassium t-butoxide (7.18g, 0.064mol) was added in one portion
to a stirred solution of (S)-N-(t-Butylcarboxy)-3-amino-2,4-
dimethyl pentan-2-ol 7 (12.39g, 0.054 mmol) in freshly distilled
(
3
CHNH), 2.22 (3H, s, CH CO), 1.60 (1H, s, CH CH), 1.46 (9H, s,
3
3
3
xCH ), 1.03 (3H, d, J 6.8, CH CH), 0.80 (3H, d, J 6.8, CH )CH);
3 3 3
δC (50MHz, CDCl3) 207.8 (CH CO), 156.2 (C=O), 79.7
THF (250mL) at 0°C. After 30 minutes, saturated NH Cl solution
4
3
(
100mL) and ethyl acetate (100mL) were added and the layers
separated. The aqueous layer was extracted with ethyl acetate
2x100mL), washed with brine (50mL) and dried over MgSO4.
(
(
OC(CH ) ), 64.6 (CHNH), 29.9 (CH CO), 28.3 (3xCH ), 27.9
3 3 3 3
CH CH), 19.8 (CH CH), 16.4 (CH CH); m/z (CI ) 160 (35%,
+
3
+
3
3
(
MH -C H ).
4
8
The solvent was evaporated to give a crude oil, which was
recrystallised from petroleum ether (40-60) / diethyl ether (6.06g,
7
8.
Gas chromatographic analysis was carried out over a Chirasil
valine stationary phase.
1%) to give the desired SuperQuat 8 as needles; m.p. 88-89°C;