A new antibiotic producing actinomyces belonging to the genus Planomonospora is described. Detailed description of its morphological and some of its biochemical characters are given. The antibiotic for which the name sporangiomycin is proposed can be produced successfully under submerged conditions. Sporangiomycin was found to belong to the depsipeptide or peptolide group of antibiotics, and is related to thiostrepton. The antibiotic is highly active in vitro against gram-positive bacteria, and protects mice from streptococcal and diplococcal infections.
The relationship between chemical structure and biological activity of leucomycins and their derivatives was examined in vivo and in vitro. The biological activity of Fr-group was higher than that of Ac-group in vitro, but the latter showed higher blood level and lower toxicity than Fr-group. Lengthening of the carbon chain in the O-acyl group at C-4 in mycarose resulted in a marked increase in the biological activity in vitro, with the isovaleryl group having the highest activity. The aldehyde group in the lactone was related to antibiotic activity, but α, β, γ, δ-unsaturated alcohol system at C9- to C12-positions was not important.
A new antibiotic, ascochlorin, C23H29O4Cl, was obtained from the filter cake of the fermented broth of Ascochytaviciae LIBERT. Ascochlorin inhibits plaque formation of both DNA and RNA viruses in the agar-diffusion plaque inhibition method. However, it showed no antiviral activity by the tube culture method. It showed cytotoxicity to chick embryo fibroblast monolayer and HeLa cells at a concentration of 0.3 meg/ml in tube culture. The anti biotic was obtained in two forms, the physical and chemical properties of which are described.
Kitasatoa kauaiensis, a new species of the genus Kitasatoa, belonging to the family Streptoplanaceae, produces 3 kinds of antibiotics in a culture broth. These antibiotics were identified as chloramphenicol, bottromycin and fradicin based on their physico-chemical and biological properties. A new differential bioassay method for chloramphenicol and bottromycin produced in the same culture broth was established.
The ditetrahydropyranyl ether of coumermycin A1 was prepared and converted to a series of new derivatives by an acyl interchange reaction. The mechanism of this interesting and useful reaction is discussed. All of the 67 semisynthetic coumermycins described are active antibiotics, and several of them show desirable changes in physical properties from those of the parent coumermycin A1. Comparative activities against Staphylococcus aureus Smith are reported.