Hydrochloric Acid → 3-{[(Tert-butoxy)carbonyl]amino}-2-hydroxypentanoic acid

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Reaction Steps

(1S)-(2-Cyano-1-ethyl-2-hydroxyethyl)carbamic acid tert-butyl ester (10 g, 46.7 mmol) was dissolved in 1,4-dioxane (100 mL). Anisole (5 mL) was added and then concentrated HCl (100 mL). The mixture was heated under reflux for 24 hours. The mixture was evaporated to dryness under vacuum and re-dissolved in 100 mL water. The solution was washed with ether and then neutralized with saturated aqueous NaHCO3. Di-tert-butyl dicarbonate (10 g, 46 mmol) was added with 1,4-dioxane (200 mL), and the mixture was stirred at ambient temperature for 24 hours. The dioxane was removed under vacuum and the remaining aqueous solution was washed with ether. The solution was acidified with 1N HCl and extracted with ethyl acetate. The combined organic layers were washed with brine, dried with magnesium sulfate and evaporated to yield 3-tert-Butoxycarbonylamino-2-hydroxy-pentanoic acid (4.5 g) as yellowish oil.

Provenance & Evidence