1. For a general discussion, see: A. Spatola, in "Chemistry and Biochemistry of Amino Acids, Peptides, and Proteins", Ed. B. Weinstein, Marcel Dekker, New York, 1983, Vol. 7, p267.

2. B. Lygo, Synlett, 1992, 793.

3. B. Lygo and C.N. Rudd, Tetrahedron Lett., 1995, 36, 3577.

4. See for example; S. Wilk, Life Sciences, 1983, 33, 2149

5. See for example; B. Imperiali, S.L. Fisher, R.A. Moats, and T.J. Prins, J. Am. Chem. Soc., 1992, 114, 3182; G.-B. Liang, C.J. Rito, and S.H. Gellman, J. Am. Chem. Soc., 1992, 114, 4440.

6. R.V. Hoffman, H.-O. Kim, Tetrahedron Lett., 1992, 33, 3579.