P. Müller, H. Imogaï / Tetrahedron: Asymmetry 9 (1998) 4419–4428
4427
155.4 (s); 171.4 (s); 175.7 (s). MS: 388 (M+, 8), 332 (46), 271 (21), 259 (14), 241 (11), 197 (14), 57 (97).
HRMS: 388.1989 (C21H28O5N2; calc. 388.1998).
3.4.4. Hydrolysis of 3h. 2-{(N-2-Trimethylsilylethoxycarbonyl)amino}-methylcyclo-prop-2-ene-1-car-
boxylic acid 8
To 3h (300 mg, 0.75 mmol) in CH2Cl2 (15 mL) was added CF3COOH (200 µL). The mixture was
stirred at 25°C during 24 h, then concentrated in vacuo. Chromatography (SiO2, hexane:AcOEt 50:50
20
afforded 8 (16 mg, 8.3%) as a transparent oil. [α]D +29 (c 1.0, CHCl3) for >97% ee (from 3g). IR
1
(film): 3500–3300w, large, 2947w, 1703s, 1506m, 1247m, 904s. H NMR (200 MHz, CDCl3): 0.37 (s,
3H); 0.95–1.03 (m, 2H); 2.28 (s, 1H); 4.12–4.23 (m, 2H); 4.30 (d, broad, J=5.4, 2H); 5.10 (s, broad, 1H);
6.57 (s, 1H); 8.60 (s, broad, 1H). 13C NMR (100 MHz, CDCl3): −1.51 (q); 17.7 (t); 20.0 (d); 36.8 (t); 63.7
(t); 96.7 (d); 112.5 (d); 156.6 (s); 180.0 (s). MS: 184 (M+−SiMe3, 7), 152 (7), 96 (17), 77 (23), 75 (85),
73 (100), 68 (22) , 67 (13), 59 (12), 52 (13), 45 (29). HRMS: 184.0610 (C8H10O4N; calc. 184.1720).
3.4.5. Catalytic hydrogenation of 4 and synthesis of lactam 10. (1S,5R)-3-Azabicyclo[3.1.0]hexan-2-one
To Pd/C (5.0 mg) in EtOH (6.0 mL) under H2 was added, by means of a syringe, the amine 4 (10.7
mg, 0.076 mmol) in EtOH at 20°C. After 90 min of stirring, the mixture was filtered through Celite.
The filtrate was dried (Na2SO4) and concentrated at 100 torr. The crude cyclopropane 9 was dissolved in
THF (5.0 mL) to which 3 drops of Et3N were added. The mixture was heated to reflux during 4 h, then
concentrated in vacuo (60 torr), and the residue was subjected to chromatography (SiO2, AcOEt:MeOH
20
20
90:10) to afford 10 (5.0 mg, 68%) as a white solid. [α]D −53 (c 1.25, CHCl3). {Lit.:6a [α]D +49 (c
1.25, CHCl3) for (1R,5S)-10.} Spectral data identical to those reported by Galeazzi et al.6a
Acknowledgements
This work was supported by the Swiss National Science Foundation (Grant No. 20-45255.95 and 20-
48156.96. The authors are indebted to Mrs. A. Pinto and J.-P. Saulnier for the routine NMR spectra and
to Ms. G. Klink for the mass spectra.
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