1. (a) Fukuyama, T.; Jow, C.-K.; Cheung, M. Tetrahedron Lett. 1995, 36, 6373. Applications to solid phase synthesis were reported as we were preparing this manuscript:
2. (b) Seitz, O. Angew. Chem., Int. Ed. 1998, 37, 3109.
3. (c) Mohamed, N.; Bhatt, U.; Just, G. Tetrahedron Lett. 1998, 39, 8213.
4. (d) Kung, P.-P.; Swayze, E. Tetrahedron Lett. 1999, 40, 5651.
5. (a) Resin bound α-amimo acids were either purchased from NovaBiochem or prepared by the following procedure. To load amino acids on Wang resin: 4 equiv. DIC, 4 equiv. Fmoc-aa-OH, 2 equiv. DMAP, DCM, rt, 45 min and double coupling. To load amino acids on Rink Amide resin: 4 equiv. Fmoc-aa-OH, 4 equiv. HBTU, 4 equiv. HOBT, 8 equiv. DIEA, NMP, rt, 1.5 h.