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Pedrosa, R.; Perez-Encabo, A. Tetrahedron Lett. 1992, 33, 2895–2898. (c) Katritzky, A. R.; Yannakopoulou, K. Synthesis
1989, 747–751.
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F. N.; Strating, J. Recl. Trav. Chim. Pays-Bas 1967, 86, 463–473.
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Lett. 1999, 40, 4449–4452. (c) Mecozzi, T.; Petrini, M. J. Org. Chem 1999, 64, 8970–8972. (d) Weygand, F.; Steglich, W.
Chem. Ber. 1965, 98, 487–503.
13. Santaniello, E.; Manzocchi, A. Synthesis 1977, 698–699.
14. Stereochemical assignments for some compounds 3 have been done by comparison with literature data: Seebach, D.; Abele,
S.; Gademann, K.; Guichard, G.; Hintermann, T.; Jaun, B.; Mattews, J. L.; Schreiber, J. V. Helv. Chim. Acta 1998, 81,
932–982. The chemical shift of the N–H proton for the syn isomer is usually around 5.4 ppm while that for the anti isomer
is around 4.9 ppm.
15. Typical experimental procedure for preparation of β-amino esters 3. To a stirred solution of sulfone 1 (1 mmol) in dry
dichloromethane (5 mL) α-bromo ester 2 (2.1 mmol) was added at room temperature. The zinc–copper couple (0.2 g)
was then added and the suspension was strirred for 1 h at room temperature. The solid was filtered and washed with
dichloromethane. The combined filtrates were washed with saturated ammonium chloride and then dried over magnesium
sulfate. After evaporation of the solvent the crude β-amino ester was purified by column chromatography. 3f: IR (KBr) ν:
3350, 1716; syn isomer: mp 43°C; 1H NMR (200 MHz, CDCl3) δ: 0.94 (t, 3H, J=7.3 Hz), 1.27 (t, 3H, J=7.1 Hz), 1.46 (s,
9H), 1.55–1.80 (m, 4H), 2.40–2.55 (m, 1H), 2.62–2.75 (m, 2H), 3.80–3.95 (m, 1H), 4.15 (q, 2H, J=7.1 Hz), 5.35 (d, 1H,
1
J=9.9Hz), 7.15–7.31 (m, 5H); anti isomer: mp 61°C; H NMR δ: 0.89 (t, 3H, J=7.3 Hz), 1.24 (t, 3H, J=7.1 Hz), 1.46 (s,
9H), 1.60–1.90 (m, 4H), 2.45–2.50 (m, 1H), 2.60–2.80 (m, 2H), 3.75–3.90 (m, 1H), 4.13 (q, 2H, J=7.1 Hz), 4.64 (d, 1H,
J=9.9 Hz), 7.15–7.35 (m, 5H).