ethyl acetate approx 150 ml and 2 n aqueous hydrochloric acid 80 ml and the ph was adjusted to approx 2 with 2 n hydrochloric acid the organic phase was separated and washed sequentially with water approx 50 ml and aqueous sodium bicarbonate approx 50 ml the aqueous phases were back extracted with ethyl acetate the combined organic solution approx 200 ml was dried over magnesium sulfate and filtered through a small silica gel pad 10 g of silica gel more ethyl acetate approx 250 ml was passed through the silica gel to elute the product an in process control showed the diastereomeric ratio to be 1 68 1 of compound 3 ii sp compound 3 i rp the solvent was removed under vacuum and the resulting foam was dissolved in mtbe 100 ml the clear solution was seeded with 3 ii sp crystals the mixture was gently stirred using rotavap for 3 hours at room temperature without vacuum and then left in a refrigerator overnight the precipitated solid was filtered off and rinsed with cold mtbe to provide 8 96 g 39 8 yield of compound 3 as an off white solid that had u02dc 99 hplc purity and was determined by chiral hplc to be an 87 13 mixture of diastereomers compound 3 ii sp compound 3 i rp the obtained off white solid of compound 3 was dissolved in dcm 30 ml ethyl acetate can be used instead of dcm to obtain similar results under reflux the resulting solution was diluted with mtbe 60 ml seeded with compound 3 ii.