L-Hydroxyproline → (2S,4R)-1-allyloxycarbonyl-2-carboxy-4-hydroxypyrrolidine

Participants

Reaction Steps

To a solution of trans-4-hydroxy-L-proline (35.9 g) and sodium hydroxide (23.9 g) in water (330 ml) was added dropwise a solution of allyl chlorocarbonate (36.3 g) in methylene chloride (250 ml) under ice-cooling, and stirring was continued for 2 hours. Aqueous layer was separated from the reaction mixture, washed twice each with methylene chloride (100 ml), and then acidified by adding concentrated sulfuric acid (25 g) dropwise at a temperature below 30° C. After adding table salt (120 g), the mixture was extracted twice each with ethyl acetate (220 ml). Extract was dried over magnesium sulfate. Distillation of the solvent gave crude crystalline trans-1-allyloxycarbonyl-4-hydroxy-L-proline (62 g). Purification of the crude crystals by repulping with toluene gave trans-1-allyloxycarbonyl-4-hydroxyl-L-proline (56.1 g) having m.p. 93-°94° C.

Provenance & Evidence