Chemistry of the actinomycins

The actinomycins are yellow-red crystalline antibiotics that are produced by various species of Streptomyces. Streptomyces is a genus ofsoil microbes that, on the basis of its morphology, has a position between the fungi and the bacteria. The actinomycins are highly toxic and cannot, therefore, be used in the treatment of infectious diseases. They are, however, of interest because in small, non-toxic dosages they have an anti-cancer effect in laboratory animals, and in man a favourable effect on Hodgkin's disease, a cancer-like disease of the lymphatic system. Moreover, it has been observed that actinomycins are able to stop the development of various human tumours, and to increase the effect of radiotherapy in the treatment of some forms of tumours-. 2. During the last few years we have been investigating the structure of the actinomycins. In the course of these studies, we have been able to clarify the constitution of some of them, and to find a method for their