1. The enantiomeric purity was determined by HPLC analysis (254 nm, 25 �C) tR 21.1 min (minor); tR 30.1 min (major) [CHIRALPAK AS-H (0.46 cm x 25 cm) (from Daicel Chemical Ind;Ltd.) hexane/i-PrOH, 90/10, 1.00 mL/min] as 78 % ee. The absolute stereochemistry was assumed by analogy