1. For reviews on cycloaddition reactions, see: (a) Comprehensive Organic Synthesis; Trost, B. M.; Fleming, I.; Paquette, L. A., Eds.; Pergamon: Oxford, 1991; Vol. 5, Chapters 1–9. (b) Advances in Cycloaddition; Curran, D. P., Ed.; JAI Press: Greenwich, 1994; Vols. 1–3.
2. (a) Alcaide, B.; Almendros, P. Tetrahedron Lett. 1999, 40, 1015. (b) Alcaide, B.; Alonso, J. M.; Aly, M. A.; Sáez, E.; Martı́nez-Alcázar, M. P.; Hernández-Cano, F. Tetrahedron Lett. 1999, 40, 5391.
3. For other related cyclization methods recently developed in our group see, for example: (a) Alcaide, B.; Rodrı́guez-Campos, I. M.; Rodrı́guez-López, J.; Rodrı́guez-Vicente, A. J. Org. Chem. 1999, 64, 5377. (b) Alcaide, B.; Polanco, C.; Sierra, M. A. J. Org. Chem. 1998, 63, 6786.
4. β-Lactam antibiotics continue to play a pre-eminent role in antibacterial therapy with the invention of new chemical entities being driven by the emergence of resistant strains of bacteria. See, for instance: (a) Hook, V. Chemistry in Britain, 1997, 33, 34. (b) Niccolai, D.; Tarsi, L.; Thomas, R. J. Chem. Commun. 1997, 2333. (c) Spratt, B. G. Science 1994, 264, 388.
5. See, for example: Symposia-in-Print Number 8, Recent Advances in the Chemistry and Biology of β-Lactams and β-Lactam antibiotics, G. I. Georg, G. (Ed.) BioMed. Chem. Lett. 1993, 3, 2159