Appendix

Abstract

The finely powdered dicyclohexylammonium salt of the protected amino acid, (5.1 g, 10 mmol) is added to a two phase system of ethyl acetate (40 ml) and a solution of KHSO₄ (2 g, 15 mmol) in water (40 ml) [2]. The mixture is shaken by hand until the dicyclohexylammonium salt is completely dissolved. The aqueous phase is extracted with ethyl acetate (twice, with 10 ml each time). The combined organic layers are washed with water until they are free of sulfate ions, then dried over anhydrous sodium sulfate and evaporated to dryness in vacuo [3].