Studies on Coprecursors of Penicillin. Part 4

In our previous report, it has been ascertained that the compounds which have the structure of_??_in the molecules often indicate coprecursor effect if R1 and R2 are hydrogen atom or aliphatic radicals. In this report, experiments have been done on the compounds which have the same funda-mental structure as the above mentioned, and yet R1 or R2 are not aliphatic, but ring formed radicals. Coprecursor activity has been studied with the following five compounds. (1)_??_ (2)_??_ (3)_??_ (4)_??_ (5)_??_ Experimental results indicate that all the compounds except the last one have no coprecursor effect. When_??_is added to culture broth together with precursors, _??_the maximum potency is enhanced but the potency in the earlier cultural stage is lowered comparing with the control culture.