Hydrochloric Acid → L-Alanyl-L-proline

Participants

Reaction Steps

N-pyruvyl-L-proline (0.085 g., 0.46 mmoles, 1.0 eq.), hydroxylamine hydrochloride (0.048 g., 0.69 mmoles, 1.5 eq.), sodium acetate (0.056 g., 0.69 mmoles, 1.5 eq.), and 2 mL water and 10 mL ethanol were added to a 25 mL flask. The suspension was heated to reflux for 2 h. The imine was transferred under nitrogen gas with 100 mL ethanol to a 250 mL Parr flask. Palladium hydroxide-on-carbon (0.02 g., 0.18 mmoles, 0.4 eq.) and hydrochloric acid (6 mL, 0.2 moles, 430 eq.) were added and nitrogen was bubbled through for 3 minutes (pH=0.1). The material was hydrogenated for 17 hours as described in Example 1, Part A, to produce a >99.5% diastereomeric excess of L-alanyl-L-proline. Isolation of the product from the reaction mixture can be accomplished by filtering the latter through Celite® , adjusting the pH to 4, and concentrating the resultant solution to one-half volume. The solid which forms is collected by filtration, and held under vacuum to remove any residue solvent.

Provenance & Evidence