Table 1. Initial experiments of SDE of (R)-1 (41.6% ee) during achiral silica-gel chromatography.

Run a	Loading solvent	Eluent	% ee min b	% ee max b	Δee c
1	DMSO	DCM/MeOH = 95/5	—	—	—
2	DMSO	H/A = 5/5	21.2	57.8	36.6
3	DMSO	H/A = 7/3	20.3	71.3	51.0
4	DMF	H/A = 7/3	25.6	66.5	40.9
5	Dioxane	H/A = 7/3	26.2	64.9	38.7

^aRegular silica-gel packed in a glass column (10 × 50 mm) was used under atmospheric pressure.

^bee was determined by HPLC using a CHIRALCEL OJ-H with ethanol as the eluate.

^cΔee = (% ee max) – (% ee min).