E. W. C. Cheng et al. / Tetrahedron 62 (2006) 12398–12407
12403
0.90 (d, 3H, J 7 Hz, CH3CHMe), 1.34 (t, 6H, J 7 Hz,
2ꢂCH3CH2O), 1.95–2.07 (m, 1H, Me2CH), 4.14 (quintet,
4H, J 7 Hz, 2ꢂCH3CH2O), 5.44 (d, 1H, J 3 Hz, NCH),
6.96 (dd, 1H, J 19, 17 Hz, CH]), 7.24–7.46 (m, 10H,
2ꢂPh), 7.90 (dd, 1H, J 21, 19 Hz, CH]); dP (109 MHz,
CDCl3) 15.2; dC (101 MHz, CDCl3) 16.70 (CH3), 16.76
(d, 1JC–P 186 Hz, PC]), 135.25 (Ph quaternary C), 135.93
(d, JC–P 10 Hz, COC]), 153.43 (O–CO–N), 163.54 (d,
2
3JC–P 28 Hz, C–CO–N); m/z (FAB) found: [M+H]+
368.1268. C17H23NO6P requires 368.1263.
4.2.4. (S)-3-[(E)-3-(Diethoxyphosphinoyl)prop-2-enoyl]-
4-benzyl-5,5-diphenyl-1,3-oxazolidin-2-one 3d. Flash
chromatography in CH2Cl2–EtOAc (85:15) gave 3d (29%
yield) as a colourless oil; [a]3D6 ꢀ218 (c 1.2, CH2Cl2);
nmax/cmꢀ1 (film) 1786 (C]O) and 1688 (C]O); dH
(270 MHz, CDCl3) 1.32 (t, 6H, J 7 Hz, 2ꢂCH3CH2), 2.76
(dd, 1H, J 14 and 8 Hz, HCHPh), 2.87 (dd, 1H, J 14 and
5 Hz, HCHPh), 4.12 (quintet, 4H, J 7 Hz, 2ꢂCH2O), 4.65
(dd, 1H, J 8 and 5 Hz, NCH–CH2), 6.70–6.75 (m, 2H, Ar–
H), 6.86 (dd, 1H, J 19 and 17 Hz, C]CHCO), 7.07–7.44
(m, 13H, Ar–H), 7.85 (dd, 1H, J 21 and 17 Hz, C]CHP);
dP (109 MHz, CDCl3) 15.1; m/z (ESI) found: [M+NH4]+
537.2155. C29H34N2O6P requires 537.2149.
2
(2ꢂCH3), 22.18 (CH3), 30.49 (CMe2), 63.06 (d, JC–P
6 Hz, 2ꢂCH2O), 65.27 (CHN), 90.20 (C–O) [125.92,
126.23, 128.49, 128.85, 129.17, 129.43, together aromatic
1
2
C], 133.28 (d, JC–P 186 Hz, PC]), 135.35 (d, JC–P
10 Hz, COC]), 138.27 (C-1 of Ph), 142.31 (C-1 of Ph),
152.88 (OCON), 163.44 (d, JC–P 28 Hz, C–C]O); m/z
3
(ESI) found: [M+NH4]+ 489.2146. C25H34N2O6P requires
489.2149.
4.2.1. 3-[(E)-3-(Diethoxyphosphinoyl)prop-2-enoyl]-1,3-
oxazolidin-2-one 3a. Flash chromatography [gradient
from CH2Cl2–Et2O (3:1) to (3:2)] gave 3a (47% yield) as
a colourless oil; nmax/cmꢀ1 (film) 1686 (C]O) and 1779
(C]O); dH (250 MHz, CDCl3) 1.38 (t, 6H, J 7 Hz,
2ꢂCH3), 4.07–4.23 (m, 6H, 2ꢂCH2OP+CH2N), 4.49 (t,
2H, J 8 Hz, CH2OCO), 7.02 (dd, 1H, J 19, 17 Hz,
C]CHCO), 7.98 (dd, 1H, J 21, 17 Hz, C]CHP); dP
(101 MHz, CDCl3) 15.0; dC (101 MHz, CDCl3) 16.66 (d,
3JC–P 6 Hz, CH3CH2O), 42.97 (CH2N) [62.90, 63.08,
63.14, together 3ꢂCH2], 132.71 (d, J 186 Hz, PC]),
135.49 (d, J 10 Hz, COC]), 153.56 (O–CO–N), 163.59
(d, J 28 Hz, C–CO–N); m/z (FAB) found: [M+H]+
278.0780. C10H17NO6P requires 278.0794.
4.3. Typical procedure for Lewis acid-promoted Diels–
Alder reaction: preparation of (4S,10R,20R,30S,40S)-[3-
(diethoxyphosphinoyl)bicyclo[2.2.2]oct-5-ene-2-carbon-
yl]-5,5-diphenyl-4-isopropyloxazolidin-2-one 10
(S)-3-[(E)-3-(Diethoxyphosphinoyl)prop-2-enoyl]-4-isopro-
pyl-5,5-diphenyl-1,3-oxazolidin-2-one 3e (0.200 g, 0.424
mmol) was dissolved in dry dichloromethane (2 mL). The
solution was cooled to ꢀ96 ꢁC under nitrogen. Cyclohexa-
1,3-diene (1.0 mL, 10.5 mmol) and 1.8 M diethylaluminium
chloride in toluene (0.37 mL, 0.66 mmol) were added to the
solution, which was stirred for 20 min at ꢀ96 ꢁC. The reac-
tion mixture was then poured into 2 M HCl (90 mL). It was
extracted with dichloromethane (40 mL) and the organic
layer was washed with saturated aqueous NaHCO3
(4ꢂ20 mL), followed by 0.4 M aqueous potassium sodium
(+)-tartrate (40 mL). The organic phase was dried (MgSO4)
and the solvent was evaporated. Analysis of the residue by
31P NMR showed complete conversion of dienophile into
a single product. Flash chromatography (EtOAc–petrol,
7:3) yielded the title compound 10 (0.166 g, 71%) as a white
solid. Recrystallisation from dichloromethane–petrol gave
colourless needles, mp 201–202 ꢁC, [a]D ꢀ73.7 (c 0.93,
CHCl3); nmax/cmꢀ1 (film) 1706 (C]O) and 1779 (C]O);
dH (400 MHz, CD2Cl2, assignments supported by COSY)
0.67 (d, 3H, J 7 Hz, CH3CHMe), 0.75 (d, 3H, J 7 Hz,
CH3CHMe), 0.81 (t, 3H, J 7 Hz, CH3CH2O), 0.96–1.08 (m,
4H, CH3CH2O+H-80a), 1.2–1.3 (m, 1H, H-70a), 1.69–1.77
(m, 1H, H-70b), 1.89–1.96 (m, 1H, CHMe2), 2.00–2.08 (1H,
m, H-80b), 2.37 (ddt, 1H, J 19, 7, 2 Hz, CHP), 2.78–2.80
(m, 1H, H-10), 3.00–3.02 (m, 1H, H-40), 3.40–3.50 (m, 1H,
CH–O), 3.56–3.66 (m, 1H, CH–O), 3.7–3.8 (m, 3H,
CH2O+CHC]O), 5.37 (d, 1H, J 3 Hz, NCH), 5.93 (t, 1H,
J 7 Hz, H-60), 6.41 (tt, 1H, J 7, 1 Hz, H-50), 7.17–7.45 (m,
10H, 2ꢂPh); dP (109 MHz, CDCl3) 31.5; dC (101 MHz,
CD2Cl2, assignments supported by HSQC) 16.18
(CH3CHMe), 16.58 (2ꢂCH3CH2O), 20.59 (C-80), 22.01
(CH3CHMe), 25.59 (C-70), 30.03 (C-10), 30.74 (CHMe2),
4.2.2. (4S,5R)-3-[(E)-3-(Diethoxyphosphinoyl)prop-2-
enoyl]-4-methyl-5-phenyl-1,3-oxazolidin-2-one 3b. Flash
chromatography [CH2Cl2–Et2O, gradient from (2:1) to
(3:2)] gave 3b (62% yield) as a colourless oil; [a]3D6 ꢀ20.6
(c 2, CHCl3); nmax/cmꢀ1 (film) 1686 (C]O) and 1782
(C]O); dH (250 MHz, CDCl3) 0.95 (d, 3H, J 7 Hz, NCH–
CH3), 1.38 (t, 6H, J 7 Hz, 2ꢂCH3CH2), 4.18 (quint, 4H,
J 7 Hz, 2ꢂCH2OP), 4.82 (quint, 1H, J 7 Hz, NCH–CH3),
5.73 (d, 1H, J 7 Hz, PhCHO), 7.03 (dd, 1H, J 19 and
17 Hz, C]CHCO), 7.29–7.44 (m, 5H, Ph), 8.01 (dd, 1H,
J 21 and 17 Hz, C]CHP); dP (101 MHz, CDCl3) 15.1; dC
3
(101 MHz, CDCl3) 14.82 (4-Me), 16.72 (d, JC–P 6 Hz,
CH3CH2O), 55.48 (C-4), 63.20 (d, JC–P 6 Hz, CH2O),
79.78 (C-5), 126.05 (Ph), 129.17 (Ph), 129.34 (Ph), 132.84
2
(d, 1JC–P 186 Hz, PC]), 133.30 (Ph quaternary C), 136.00
(d, JC–P 9 Hz, COC]), 153.02 (O–CO–N), 163.31 (d,
2
3JC–P 28 Hz, C–CO–N); m/z (EI) found: M+ 367.1184.
C17H22NO6P requires 367.1185.
4.2.3. (S)-3-[(E)-3-(Diethoxyphosphinoyl)prop-2-enoyl]-
4-benzyl-1,3-oxazolidin-2-one 3c. Flash chromatography
[gradient from CH2Cl2–Et2O (2:1) to (3:2)] gave 3c (84%
yield) as a colourless oil; [a]3D6 +52.2 (c 2.26, CHCl3);
nmax/cmꢀ1 (film) 1684 (C]O) and 1782 (C]O); dH
(250 MHz, CDCl3) 1.38 (t, 6H, J 7 Hz, 2ꢂCH3CH2), 2.82
(dd, 1H, J 13 and 9 Hz, HCHPh), 3.35 (dd, 1H, J 13 and
3 Hz, HCHPh), 4.12–4.30 (m, 6H, 3ꢂCH2O), 4.69–4.79
(m, 1H, NCH–CH2), 7.06 (dd, 1H, J 19 and 17 Hz,
C]CHCO), 7.19–7.38 (m, 5H, Ph), 7.99 (dd, 1H, J 21
and 17 Hz, C]CHP); dP (101 MHz, CDCl3) 15.8; dC
1
2
35.31 (d, JC–P 141 Hz, CP), 35.45 (d, JC–P 5 Hz, C-40),
2
2
43.32 (d, JC–P 4 Hz, CH–C]O), 61.62 (d, JC–P 7 Hz,
CH2O), 61.92 (d, JC–P 7 Hz, CH2O), 64.68 (CHN), 89.29
2
3
(101 MHz, CDCl3) 16.72 (d, JC–P 6 Hz, CH3CH2O),
37.93 (CH2Ph), 55.69 (C-4), 63.24 (d, JC–P 6 Hz, CH2O),
66.96 (C-5), 127.86 (Ph), 129.41 (Ph), 129.79 (Ph), 132.84
(O–CPh2), 125.71 (Ph), 126.12 (Ph), 128.25 (Ph), 128.79
(Ph), 128.91 (Ph), 129.28 (Ph), 129.88 (C-60), 137.54 (d,
3JC–P 18 Hz, C-50), 138.77 (Ph quaternary C), 143.12 (Ph
2