Abstract: Two thiomarinol derivatives, which have antibacterial and anti-mycoplasmal properties, are obtainable from microorganisms of the genus Alteromonas and are named "thiomarinol B" and "thiomarinol C". Thiomarinol B can also be prepared by the oxidation of thiomarinol.

Abstract: The process for producing mureidomycin A, B, C or D or a salt thereof by cultivating Streptomyces flavidovirens SANK 60486, FERM BP-1347, in a culture medium therefor and isolating mureidomycin A, B, C or D or a salt thereof from the cultured broth.

Abstract: New antibiotics of the mureidomycin group have the formula ##STR1##wherein X represents the group ##STR2##and wherein R represents hydrogen, an alkyl group having from 1 to 10 carbon atoms, an alkenyl group having from 2 to 7 carbon atoms, an alkynyl group having from 3 to 7 carbon atoms, an aryl group having from 6 to 10 carbon atoms, an aralkyl group having from 7 to 10 carbon atoms, or one of the said aryl or aralkyl groups substituted with at least one substituent selected from halogen and alkyl groups having from 1 to 5 carbon atoms. The compound in which X represents 8-hydroxy-1,2,3,4-tetrahydroisoquinolin-3-yl is named mureidomycin E and the compound in which X represents 6-hydroxy-1,2,3,4-tetrahydroisoquinolin-3-yl is named mureidomycin F. This group of compounds and their pharmaceutically acceptable esters and salts are useful as antibiotics for the treatment of bacterial infections.

Abstract: Novel compounds, called mureidomycins A, B, C and D, may be prepared by cultivation of a suitable microorganism of the genus Streptomyces, especially Streptomyces flavidovirens SANK 60486 (FERM P-8636, FERM BP-1347). These represent a wholly new class of antibiotics, which are valuable in the treatment of infections caused by a variety of bacteria, notably of the genus Pseudomonas.