Lithium hydroxide, monohydrate → (4S,5R)-3-(tert-Butoxycarbonyl)-2,2-dimethyl-4-phenyl-1,3-oxazolidine-5-carboxylic acid

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Reaction Steps

A solution of 4.62 g of lithium hydroxide hydrate in 80 cm3 of water is added in the course of 10 minutes to a stirred solution of 12.8 g of ethyl (4S,5R)-3-tert-butoxycarbonyl-2,2-dimethyl-4-phenyl-5-oxazolidinecarboxylate in 200 cm3 of ethanol. After stirring for a further 10 minutes, the reaction medium is concentrated to dryness under reduced pressure (2.7kPa) at a temperature in the region of 40° C. The residue obtained is dissolved in 70 cm3 of water and then extracted with 3 times 20 cm3 of isopropyl ether. The aqueous phase is then acidified to a pH in the region of 2.6 by adding approximately 100 cc of 1N aqueous hydrochloric acid solution and thereafter extracting with 3 times 50 cm3 of dichloromethane. The combined organic phases are dried over magnesium sulphate, filtered and then concentrated to dryness under reduced pressure (2.7 kPa) at a temperature in the region of 40° C. 11.3 g of (4S,5R)-3-tert-butoxycarbonyl-2,2-dimethyl-4-phenyl-5-oxazolidinecarboxylic acid are thereby obtained in the form of a yellow oil, the characteristics of which are as follows:

Provenance & Evidence