organic base such as for example pyridine n n dimethylaniline n n diethylaniline etc the reaction will take from about 15 minutes to about 4 hours the resulting reaction products i e the benzothiazole of formula iv and the 6 u03b2 amino penicillin or 7 u03b2 amino cephalosporin of formula v are separated by conventional techniques such as for example column chromatography the compounds of formula v are of course valuable as intermediates which can then be acylated so as to yield various antibacterially active penicillins and cephalosporins the carboxy protecting group r can be removed after the acylation reaction also in the case of the cephalosporins wherein x is str9 other groups can be introduced at this position of the cephalosporin nucleus by known reactions the carboxy protecting group represented by the symbol r in the preceding formulas include for example straight or branched chain lower alkyl of 1 to 4 carbons benzyl p nitrobenzyl p methoxybenzyl benzhydryl 2 2 2 trichloroethyl si ch 3 3 str10 wherein r 7 is hydrogen chloro or bromo str11 the term hetero as used in the definition of the symbol x in the preceding formulas includes unsubstituted or substituted 5 or 6 membered rings having one or more n o or s atoms as for example str12 wherein r 8 is hydrogen or straight or branched chain lower alkyl of 1 to 4 carbons especially methyl the cephalosporins of formula i wherein x is s hetero are obtained by a displacement reaction.