Hydrochloric Acid → Ninhydrin

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The title compound was prepared by a modification of the procedure by Heimer et al. (Int. J Pept., 1984, 23, 203-211). N-(2-Aminoethyl)glycine (1, 3 g, 25.4 mmol) was dissolved in water (50 mL), dioxane (50 mL) was added, and the pH was adjusted to 11.2 with 2N sodium hydroxide. tert-Butyl-4-nitrophenyl carbonate (7.29 g, 30.5 mmol) was dissolved in dioxane (40 mL) and added dropwise over a period of 2 h, during which time the pH was maintained at 11.2 with 2N sodium hydroxide. The pH was adjusted periodically to 11.2 for three more hours and then the solution was allowed to stand overnight. The solution was cooled to 0° C. and the pH was carefully adjusted to 3.5 with 0.5M hydrochloric acid. The aqueous solution was washed with chloroform (3×200 mL), the pH adjusted to 9.5 with 2N sodium hydroxide and the solution was evaporated to dryness, in vacuo (14 mm Hg). The residue was extracted with DMF (25 mL+2×10 mL) and the extracts filtered to remove excess salt. This results in a solution of the title compound in about 60% yield and greater than 95% purity by tlc (system 1 and visualised with ninhydrin, Rf =0.3). The solution was used in the following preparations of BOC-aeg derivates without further purification.

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