Patent ID: 8324417

Claim:
A process for the preparation of a (S)-alkyl 2-amino-5-cyclopropyl-4,4-difluoropentanoate hydrochloride of Formula 1: or salt thereof, where R 1 is a primary or secondary alkyl having 1 to 5 carbon atoms, which process comprises: (a) selectively hydrolyzing a compound of Formula 2: where PG is an amino protecting group and R 2 is alkyl, cycloalkyl, cycloalkylalkyl or arylalkyl, wherein any alkyl group comprising R 2 is a primary or secondary alkyl having 1 to 5 carbon atoms, to give a mixture of protected (R)-2-amino-5-cyclopropyl-4,4-difluoropentanoate and protected (S)-2-amino-5-cyclopropyl-4,4-difluoropentanoic acid; (b) isolating the protected (S)-2-amino-5-cyclopropyl-4,4-difluoropentanoic acid; (c) deprotecting the protected (S)-2-(amino)-5-cyclopropyl-4,4-difluoropentanoic acid to give (S)-2-amino-5-cyclopropyl-4,4-difluoropentanoic acid; (d) treating the (S)-2-amino-5-cyclopropyl-4,4-difluoropentanoic acid with alcohol R 1 OH; (e) optionally converting the free base of the compound of Formula I to the acid addition salt.