a compound having the formula str26 or a nontoxic pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier therefor there is further provided by the present invention a method of treating bacterial infections comprising administering by injection to an infected warm blooded animal including man an effective but nontoxic dose of 250 1000 mgm of a compound having the formula str27 wherein r 1 is alkyl containing 1 4 carbon atoms and r 2 is hydrogen pivaloyloxymethyl acetoxymethyl methoxymethyl acetonyl phenacyl p nitrobenzyl u03b2 u03b2 u03b2 trichloroethyl 3 phthalidyl or 5 indanyl or a nontoxic pharmaceutically acceptable salt thereof said compound being at least 75 by weight in the form of its syn isomer and preferably in the form of its syn isomer essentially free of the corresponding anti isomer there is further provided by the present invention a method of treating bacterial infections comprising administering by injection to an infected warm blooded animal including man an effective but nontoxic dose of 250 1000 mgm of the syn isomer of a compound having the formula str28 or a nontoxic pharmaceutically acceptable salt thereof there is also provided by the present invention a method for combatting haemophilus infections which comprises administering to a warm blooded mammal infected with an haemophilus infection an amount effective for treating said haemophilus infection of a composition comprising a compound having the formula str29 wherein r 1 is alkyl containing 1 4 carbon atoms and r 2 is hydrogen pivaloyloxymethyl acetoxymethyl methoxymethyl acetonyl phenacyl p nitrobenzyl u03b2 u03b2 u03b2.