Inhibition of the incorporating of chloride into the tetracycline molecule.

Bromide and thiocyanate have been shown to be effective inhibitors of the chlorination process leading to chlortetracycline formation by certain strains of Streptomyces aureofaciens Duggar (Gourevitch et al., 1955; Doerschuk, et at., 1956). Sekizawa (1955) reported thiourea, 2-thiouracil, 2-mercaptobenzothiazole, and thioglycolic-f3-aminonaphthalide (thionalide) to inhibit chlorination by this organism leading to the production of tetracycline rather than chlortetracyline. The present paper summarizes the work in our laboratories on the effectiveness of a number of compounds, some of which have antithyroid activity (Astwood et al., 1945) as chlorination inhibitors in an S. aureofaciens chlortetracycline synthesizing system.'