of the active ingredient however in general it is preferably to employ a dosage amount in the range of from about 100 mg to 1000 mg in parenteral administration the unit dosage is usually the pure compound in a slightly acidified sterile water solution or in the form of a soluble powder intended for solution especially preferred pharmaceutically acceptable salts and esters involving the carboxyl group of compounds of the present invention i are disclosed and claimed in u s patent application ser no 861 314 filed dec 16 1977 now u s pat no 4 181 733 issued jan 1 1980 which application is directed inter alia to pharmaceutically acceptable salts and esters of the carboxyl group of thienamycin it is precisely these salts and esters which are preferred in the present invention and they are prepared in a manner analogous to that disclosed in u s patent application ser no 861 314 which is incorporated herein by reference thus especially preferred salts include sodium potassium ammonium and the like and especially preferred esters include pivaloxymethyl p t butylbenzyl 5 indanyl 3 phthalidyl 3 methyl 2 butenyl and the like one should note that when in the total synthesis outlined above r 7 is a pharmaceutically acceptable ester moiety there is no need for the final deblocking step if it is desired to have the final product i in the form of.