Preparation and Transmetallation of Enantioenriched α-Aminoorganostannanes
low colour. Once this addition was complete, the solution was
stirred for 20 min (or 15 min) at the same temperature. Then, elec-
trophile (2 mmol) was added, and the reaction mixture was
quenched at the same temperature after 20 min (or 30 min) by the
addition of saturated aqueous NH4Cl. The aqueous phase was ex-
tracted with diethyl ether (3ϫ10 mL). The combined organic ex-
tract was dried (MgSO4) and filtered, and the solvents were evapo-
rated in vacuo. Purification by chromatography on silica gel af-
forded the desired products.
–10.9 ppm. IR (neat): ν = 2956, 2928, 2857, 1670, 1421, 1366, 1171,
˜
1104, 836, 775, 699 cm–1. MS (CI): m/z = 544 [M + H]+. HRMS
(ESI): calcd. for C24H45NO3NaSi120Sn [M + Na]+ 566.2088; found
566.2108.
2-{(tert-Butoxycarbonyl)[(1R)-2-(tert-butyldimethylsiloxy)-1-
phenylethyl]amino}propanoic Acid (ent-5c): The crude product was
1
analysed by H NMR spectroscopy and found to be a mixture of
ent-5c-anti/ent-5c-syn in a 95:5 ratio. Purification by chromatog-
raphy on silica gel (gradient elution, hexanes/diethyl ether,
100:0ǞCH2Cl2/MeOH, 90:10) gave ent-5c-anti and ent-5c-syn as
tert-Butyl [(1R)-(2-tert-Butyldimethylsiloxy)-1-phenylethyl][1-(1-hy-
droxycyclohexyl)ethyl]carbamate (ent-5a): The crude product was
colourless oils (77%). IR (neat): ν = 3378, 3064, 2955, 2928, 2856,
˜
1
1700, 1419, 1165, 837, 774, 699 cm–1. MS (CI): m/z = 424
analysed by H NMR spectroscopy and found to be a mixture of
[M + H]+.
ent-5a-anti/ent-5a-syn in a 92:8 ratio. Purification by chromatog-
raphy on silica gel (gradient elution, hexanes/diethyl ether,
1
Diastereomer ent-5c-anti: [α]2D0 = –36.7 (c = 1.0, CHCl3). H NMR
100:0Ǟ95:5). Yield: 60%. IR (neat): ν = 3379, 2931, 2856, 1661,
˜
(300 MHz, C6D6, 300 K, Me4Si): δ = 0.05 [s, 6 H, Si(CH3)2], 0.92
[s, 9 H, SiC(CH3)3], 1.14 (d, J = 6.8 Hz, 3 H, CH3CHN), 1.46 [s,
9 H, OC(CH3)3], 3.48 (q, J = 6.8 Hz, 1 H, CH3CHN), 3.78–4.02
1438, 1343, 1170, 838, 775 cm–1. MS (CI): m/z = 478 [M + H]+.
HRMS (ESI): calcd. for C27H47NO4NaSi [M + Na]+ 500.3172;
found 500.3165.
3
3
(m, 2 H, CH2OSi), 5.76 (m, 1 H, CHPh), 6.90–7.25 (m, 5 H, C6H5),
9.22 (br. s, 1 H, CO2H) ppm. 13C NMR (75 MHz, C6D6, 300 K,
Me4Si): δ = –5.7 [2 C, Si(CH3)2], 16.2 (1 C, CH3CHN), 18.4 [1 C,
SiC(CH3)3], 26.0 [3 C, SiC(CH3)3], 28.2 [3 C, OC(CH3)3], 52.4 (1
C, CH3CHN), 58.1 (1 C, CHPh), 61.4 (1 C, CH2OSi), 81.6 [1 C,
OC(CH3)3], 127.7–128.8 (5 C, C6H5), 137.2 (1 C, C6H5), 155.1 (1
C, C=O carbamate), 173.4 (1 C, C=O acid) ppm.
Diastereomer ent-5a-anti: White crystals., m.p. 91 °C (CH3CN).
[α]2D0 = +17.2 (c = 1.0, CHCl3). 1H NMR (300 MHz, C6D6, 300 K,
Me4Si): δ = 0.10 (s, 3 H, SiCH3), 0.14 (s, 3 H, SiCH3), 0.95 [s, 9
3
H, SiC(CH3)3], 1.10 (d, J = 7.4 Hz, 3 H, CH3CHN), 1.38 [s, 9 H,
2
3
OC(CH3)3], 1.35–2.20 [m, 10 H, (CH2)5], 3.88 (dd, J = 9.4 Hz, J
3
= 4.9 Hz, 1 H, CH2OSi), 4.05 (m, 1 H, OH), 4.24 (q, J = 7.4 Hz,
1 H, CH3CHN), 5.08 (dd, J = 10.7 Hz, J = 4.9 Hz, 1 H, CHPh),
3
3
Diastereomer ent-5c-syn: 1H NMR (300 MHz, C6D6, 300 K,
Me4Si): δ = 0.11 [s, 3 H, Si(CH3)2], 0.13 [s, 3 H, Si(CH3)2], 0.98 [s,
3
2
5.31 (dd, J = 10.7 Hz, J = 9.4 Hz, 1 H, CH2OSi), 7.00–7.45 (m,
5 H, C6H5) ppm. 13C NMR (75 MHz, C6D6, 300 K, Me4Si): δ =
–5.2 [2 C, Si(CH3)2], 13.2 (1 C, CH3CHN), 18.5 [1 C, SiC(CH3)3],
22.5 (1 C, CH2), 26.1 [4 C, CH2 + SiC(CH3)3], 28.5 [3 C, OC-
(CH3)3], 34.5 (1 C, CH2), 36.3 (1 C, CH2), 37.0 (1 C, CH2), 59.7 (1
C, CH3CHN), 61.7 (1 C, CHPh), 66.9 (1 C, CH2OSi), 74.4 (1 C,
COH), 79.2 [1 C, OC(CH3)3], 127.1–128.9 (5 C, C6H5), 141.4 (1 C,
C6H5), 156.9 (1 C, C=O) ppm.
3
9 H, SiC(CH3)3], 1.50 [s, 9 H, OC(CH3)3], 1.64 (d, J = 6.9 Hz, 3
3
H, CH3CHN), 3.78 (br. q, J = 6.9 Hz, 1 H, CH3CHN), 4.08–4.21
(m, 2 H, CH2OSi), 5.35 (m, 1 H, CHPh), 7.11–7.50 (m, 5 H, C6H5),
8.60 (br. s, 1 H, CO2H) ppm. 13C NMR (75 MHz, C6D6, 300 K,
Me4Si): δ = –5.4 [2 C, Si(CH3)2], 17.1 (1 C, CH3CHN), 18.3 [1 C,
SiC(CH3)3], 26.0 [3 C, SiC(CH3)3], 28.4 [3 C, OC(CH3)3], 53.7 (1
C, CH3CHN), 61.4 (1 C, CHPh), 62.9 (1 C, CH2OSi), 80.8 [1 C,
OC(CH3)3], 126.2–130.8 (5 C, C6H5), 138.1 (1 C, C6H5), 154.9 (1
C, C=O carbamate), 177.6 (1 C, C=O acid) ppm.
Diastereomer ent-5a-syn: White crystals, m.p. 110 °C (CH3CN). 1H
NMR (400 MHz, C6D6, 320 K, Me4Si): δ = 0.04 (s, 3 H, SiCH3),
0.05 (s, 3 H, SiCH3), 0.70–2.10 [m, 10 H, (CH2)5], 0.94 [s, 9 H,
SiC(CH3)3], 1.43 [s, 9 H, OC(CH3)3], 1.50 (d, 3J = 6.2 Hz, 3 H,
CH3CHN), 3.05 (m, 1 H, CH3CHN), 3.97–4.12 (m, 2 H, CH2OSi),
5.21 (br. t, 3J = 7.2 Hz, 1 H, CHPh), 7.00–7.30 (m, 5 H, C6H5)
ppm. 13C NMR (75 MHz, C6D6, 300 K, Me4Si): δ = –5.7 [2 C,
Si(CH3)2], 13.2 (1 C, CH3CHN), 18.3 [1 C, SiC(CH3)3], 22.2 (1 C,
CH2), 25.9 [3 C, SiC(CH3)3], 26.5 (1 C, CH2), 28.5 [3 C, OC-
(CH3)3], 35.6 (2 C, CH2), 37.8 (1 C, CH2), 61.8 (1 C, CH3CHN),
62.9 (1 C, CH2OSi), 63.6 (1 C, CHPh), 71.8 (1 C, COH), 80.5 [1
C, OC(CH3)3], 127.7–128.9 (5 C, C6H5), 139.0 (1 C, C6H5), 157.1
(1 C, C=O) ppm.
tert-Butyl [1-(Diethoxyphosphoryl)ethyl][(1R)-2-(tert-butyldimethyl-
siloxy)-1-phenylethyl]carbamate (ent-5d): The crude product was
1
analysed by H NMR spectroscopy and found to be a mixture of
ent-5d-anti/ent-5d-syn in a 85:15 ratio. After flash chromatography
on silica gel (gradient elution, hexanes/diethyl ether, 95:5Ǟ20:80),
pure diastereomers ent-5d-anti and ent-5d-syn (230 mg, 75%) were
obtained as colourless oils. IR (neat): ν = 2977, 2956, 2930, 2857,
˜
1695, 1422, 1387, 1252, 1053, 1024, 838, 777 cm–1. MS (ESI): m/z
= 516 [M + H]+. HRMS (ESI): calcd. for C25H46NO6PSiNa [M +
Na]+ 538.2730; found 538.2734.
tert-Butyl [(1R)-2-(tert-Butyldimethylsiloxy)-1-phenylethyl)][(1S)-1- Diastereomer ent-5d-anti: Rf = 0.42 (hexanes/diethyl ether, 30:70).
(trimethylstannyl)ethyl]carbamate (ent-5b-anti): Purification by
chromatography on silica gel (gradient elution, hexanes/diethyl
ether, 100:0Ǟ90:10) gave ent-5b-anti as a colourless oil (69%).
[α]2D0 = +30.8 (c = 0.96, CHCl3). 1H NMR (300 MHz, [D8]THF,
300 K, Me4Si): δ = 0.06 [s, 6 H, Si(CH3)2], 0.88 [s, 9 H, SiC-
3
(CH3)3], 1.18 (dd, JH,P = 15.3 Hz, 3J = 6.5 Hz, 1 H, CH3CHP),
1
[α]2D0 = –51.5 (c = 1.0, CHCl3). H NMR (300 MHz, C6D6, 300 K,
1.26 (t, 3J = 7 Hz, 3 H, OCH2CH3), 1.27 (t, 3J = 7 Hz, 3 H,
OCH2CH3), 1.38 [s, 9 H, OC(CH3)3], 4.04–4.20 (m, 6 H, CH3CHP,
OCH2CH3, CH2OSi), 4.32 (m, 1 H, CH2OSi), 4.82 (m, 1 H,
Me4Si): δ = 0.06 [s, 3 H, Si(CH3)2], 0.08 [s, 3 H, Si(CH3)2], 0.31 [s,
2JSn,H = 51 Hz, 9 H, (CH3)3Sn], 0.93 [s, 9 H, SiC(CH3)3], 1.18 (d,
3
3J = 7.4 Hz, 3 H, CH3CHN), 1.40 [s, 9 H, OC(CH3)3], 2.89 (q, J CHPh), 7.2–7.5 (m, 5 H, C6H5) ppm. 13C NMR (75 MHz, [D8]-
2
3
= 7.4 Hz, JSn,H = 53 Hz, 1 H, CH3CHN), 4.12 (d, J = 7.2 Hz, 2
THF, 300 K, Me4Si): δ = –5.2 [1 C, Si(CH3)2], –5.0 [1 C, Si-
H, CH2OSi), 5.21 (br. t, J = 7.2 Hz, 1 H, CHPh), 7.00–7.50 (m, 5
(CH3)2], 14.4 (d, 2JP,C = 5 Hz, 1 C, CHCH3), 17.0 (2 C, OCH2CH3),
3
H, C6H5) ppm. 13C NMR (75 MHz, C6D6, 300 K, Me4Si): δ = –7.8 19.0 [1 C, SiC(CH3)3], 26.5 [3 C, SiC(CH3)3], 28.7 [3 C, OC-
1
[3 C, (CH3)3Sn], –5.4 [2 C, Si(CH3)2], 18.2 (1 C, CH3CHN), 18.6 (CH3)3], 49.8 (d, JP,C = 156 Hz, 1 C, CHP), 61.5 (1 C, CHC6H5),
[1 C, SiC(CH3)3], 26.1 [3 C, SiC(CH3)3], 29.6 [3 C, OC(CH3)3], 52.4 62.0 (1 C, CH2CH3), 62.7 (1 C, CH2CH3), 66.9 (1 C, CH2OSi),
(1 C, CH3CHN), 63.0 (1 C, CHPh), 63.7 (1 C, CH2OSi), 79.7 [1 C, 80.9 [1 C, OC(CH3)3], 127.6 (1 C, C6H5), 128.7 (4 C, C6H5), 142.1
OC(CH3)3], 128.0–128.4 (5 C, C6H5), 140.0 (1 C, C6H5), 155.9 (1 (1 C, C6H5), 155.6 (1 C, C=O) ppm. 31P NMR (121 MHz, [D8]-
C, C=O) ppm. 119Sn NMR (112 MHz, C6D6, 300 K, Me4Sn): δ =
THF, 300 K, H3PO4): δ = 26.9 ppm.
Eur. J. Org. Chem. 2008, 3344–3351
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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