Patent ID: 7452990

Claim:
A 4-halo-2-oxyimino-3-oxo butyric acid-N,N-dimethyl formiminium chloride chlorosulfate of formula (I) useful in the preparation of cephalosporin antibiotics wherein X is chlorine or bromine; R is hydrogen, C 1-4 alkyl group, a hydroxyl protective group selected from trialkyl silyl ethers; trialkyl aryl silyl ethers; trialkyl stannyl ethers; trityl; tetrahydropyranyl; alkyl or aryl sulphonates selected from tosyl, mesyl, and besyl; boron or aluminum containig two alkyl groups; unsubstituted benzyl; or —CH 2 COOR 5 , or —C(CH 3 ) 2 COOR 5 ; wherein R 5 is hydrogen; or a hydrolysable ester group selected from lower alkyl esters; alkanoyloxy alkyl esters selected from acetoxy methyl, pivaloxy methyl, 1-acetoxy ethyl, and 1-pivaloxyethyl; lower alkoxycarbonyloxyalkyl esters; alkoxymethyl esters; lower alkyl amino methyl; benzyl ester; and cyanomethyl ester.