PROCEDURE FOR PREPARING CEPHALEXIN OR A BIS-DIMETHYL FORMAMIDE SOLVATE THEREOF

摘要

1472746 Cephalexin solvate GLAXO LABORATORIES Ltd 14 June 1974 [5 July 1973] 32111/73 Heading C2C A bis-dimethyl formamide solvate of cephalexin is produced by (a) acylating a silylated derivative of 7-aminodesacetoxy cephalosporanic acid (7-ADCA) by reaction with phenyl glycyl chloride hydrochloride in dimethyl formamide at a temperature not exceeding 0‹ C. in the presence of a tertiary nitrogen base having a pKa in the range 3À0-7À0 and (b) precipitating the cephalexin product so formed as a bisdimethyl formamide solvate by diluting the reaction solution with water and adjusting the pH to about 6À9 by addition of a base. Bases used in (a) include pyridine, quinoline and homologues and/or substituted derivatives thereof. After the acylation (a), the resulting solution may be treated with a compound containing active hydrogen, e.g. water, an alcohol or phenol, to remove any silyl groups present in the cephalexin reaction product before step (b). Silylated derivatives of 7-ADCA may be prepared using as silylating agent a halosilane or a silazane.