Fig. 3

Substrate scope. Reactions were run using 1 (0.15 mmol), 2 (0.30 mmol), and 4a (0.015 mmol) in CH₂Cl₂ (0.30 ml). Yields represent material isolated after silica gel column chromatography. Diastereomeric ratios (dr) were determined by ¹H NMR spectroscopy. *Reaction was run for 72 h