| 摘要 |
1321265 Preparing 7-amino cephalosporins GLAXO LABORATORIES Ltd 6 Aug 1970 [10 July 1970] 33697/70 Heading C2A 7#-Aminocephem-4-carboxylic acids and esters thereof are prepared by N-deformylating a 7#-formamidocephem-4-carboxylic acid of formula: wherein X is H, OH, O-acetyl or the residue of a nucleophile, Y is H or a oarboxyl-blocking group, and the dotted line indicates a double bond in the 2,3- or 3,4-position, by treatment with a Lewis acid in a C 1 -C 6 alkanol or a C 2 -C 6 alkane diol under substantially anhydrous conditions. The term "substantially anhydrous" means that the reaction mixture contains not more than about 1% by weight (preferably less than 0À5% by weight) of water. The Lewis acid may be phosphorus oxychloride, thionyl chloride, phosphorus trichloride or tribromide, anydrous HCl or HBr, SiCl 4 , acetyl trichloride or tribromide, p-toluene sulphonyl chloride, trichlorosilane, dimethylsilyldichloride, trimethylsilylchloride or phosgene. Suitable alkanols are methanol, ethanol and isopropanol, alkane diols may be ethylene glycol, propane 1,2-diol and propane 1,3-diol. A diluent, which may be the alkanol or alkane diol or an inert organic solvent, is preferably included, and after reaction the 7#-amino product may be precipitated as a salt which is insoluble in the reaction medium or by bringing the mixture to the isoelectric point of the 7#-amino compound. The invention includes a process comprising N-formylating a 7#-aminocephem-4-carboxylic acid (e.g. with formic acid and a C 1 -C 6 alkanoic acid anhydride or by treatment with a formic acid ester such as ethyl formate), effecting one or more reactions in the 1, 2, 3 or 4 position of the N-formylated compound, and then N-deformylating the resulting compound by the aforesaid procedure. |
