1. Jacobsen, E. N.; Zhang, W.; Muci, A. R.; Ecker, J. R.; Deng, L. J. Am. Chem. Soc. 1991, 113, 7063.
2. Also see: Irie, R.; Noda, K.; Ito, Y.; Matsumoto, N.; Katsuki, T. Tetrahedron Lett. 1990, 31, 7345; Tokunage, M.; Larrow, J. F.; Kakiuchi, F.; Jacobsen, E. N. Science 1997, 277, 936.
3. Lopez, J.; Liang, S.; Bu, X. R. Tetrahedron Lett. 1998, 39, 4199.
4. A typical procedure for 3a: To an ethanol solution (20 mL) of the chiral half unit (1.1 mmol) was added dropwise8 2,4-pentanedione (1.1 mmol) in 10 mL of ethanol at ambient temperature. The mixture was gradually heated to 60°C and then this temperature was maintained for 5 hours. The solvent was removed under vacuum to give a yellow oil, which was redissolved in hot hexane. Upon cooling at −20°C, 3a was collected with a pipette as a yellow oil and dried under vacuum, yield 0.31 g, 95%. Anal. for C18H24N2O2: C: 72.04, H: 7.81. Calcd C: 72.00, H: 8.00.
5. Rogers, M. T.; Burdett, J. L. Can. J. Chem. 1965, 43, 1516. Also see: Gero, A. J. Org. Chem. 1954, 19, 469.