GENERAL STEPS: Example 1 Preparation of N-(tert-butoxycarbonyl)-3-chloro-L-alanine
To a 50% aqueous 1,4-dioxane solution containing 1.0 g (6.25 mmol) of 3-chloro-L-alanine and 1.3 mL of triethylamine, 1.69 g (6.90 mmol) of 2-(tert-butoxycarbonyloxyimino)-2-phenylacetonitrile was slowly added under stirring at room temperature. After the reaction lasted for 2 hours, the reaction mixture was poured into 20 mL of water and extracted twice with ethyl acetate. The organic layers were combined and washed sequentially with water twice and saturated brine once, followed by drying with anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure to give 0.66 g (40.5% yield) of white solid product. For further purification, recrystallization was carried out using a solvent mixture of ethyl acetate and n-hexane to give 0.58 g of pure product (35.6% yield) with a melting point of 123-124 °C (decomposition). The structure of the product was confirmed by IR and NMR analysis.
