Abstract: New compounds, which we have named the "Leustroducsins" have the formula (I): ##STR1## in which R represents a 5-methylhexanoyloxy group, a 6-methyloctanoyloxy group or a 7-methyloctanoyloxy group, and salts thereof, and may be prepared by fermentation using a microorganism of the genus Streptomyces, especially a strain of the species Streptomyces platensis, such as strain SANK 60191 (FERM BP-3288). These compounds may be used for the treatment or prophylaxis of: adverse reactions resulting from cancer chemotherapy or radiotherapy; infections; cancer; cerebral dysfunction; and fungal infections.

Abstract: New compounds, which we have named the "Leustroducsins" have the formula (I): ##STR1## in which R represents a 5-methylhexanoyloxy group, a 6-methyloctanoyloxy group or a 7-methyloctanoyloxy group, and salts thereof, and may be prepared by fermentation using a microorganism of the genus Streptomyces, especially a strain of the species Streptomyces platensis, such as strain SANK 60191 (FERM BP-3288). These compounds may be used for the treatment or prophylaxis of: adverse reactions resulting from cancer chemotherapy or radiotherapy; infections; cancer; cerebral dysfunction; and fungal infections.

Abstract: 5-Amino-1-(hydroxymethyl)cyclopentane-1,2,3,4-tetraol and 2-amino-4-(hydroxymethyl)-3a,5,6,6a-tetrahydro-4H-cyclopent[d]oxazole-4,5, 6-triol, which have the ability to inhibit the activity of sugar hydrolases, especially .beta.-glucosidase and sucrase and can thus be used for the treatment and prophylaxis of tumorous conditions, AIDS, diabetes and obesity, can be prepared by hydrolysis of trehazolin. 2-Amino-4-(hydroxymethyl)-3a,5,6,6a-tetrahydro-4H-cyclopent[d]oxazole-4,5, 6-triol can also be prepared by fermentation using newly isolated strains Micromonospora sp. SANK 62390, FERM BP-3521 and Amycolatopsis sp. SANK 60791, FERM BP-3513.

Abstract: Novel compounds, called chloropolysporins B and C, and salts thereof have antibiotic properties and would appear to be members of the class of glycopeptide antibiotics containing chlorine. They may be produced by cultivating a suitable strain of miroorganism of the genus Micropolyspora, especially Micropolyspora sp. SANK 60983 (FERM BP-538). They may be combined with conventional pharmaceutically acceptable carriers or diluents for therapeutic use or incorporated into edible excipients, such as feed or water, for use as a growth-promoting agent, especially for farm animals.

Abstract: Propioxatins A and B, which have the formula: ##STR1## wherein R represents a hydrogen atom or a methyl group, can be prepared by cultivating a suitable strain of Kitasatosporia, e.g. Kitasatosporia sp. SANK 60684 (FERM-P 7581). They can be salified to give pharmaceutically acceptable salts. The compounds are active as enkephalinase B inhibitors and are thus capable of enhancing enkephalin activity in vivo.

Abstract: Mycoplanecin derivatives of formula (I): ##STR1## [wherein: R represents a hydrogen atom, an N-(.alpha.-ketobutyryl)-N-methylvalyl group or an N-(.alpha.-hydroxybutyryl)-N-methylvalyl group;R.sup.1 represents a methyl group or an ethyl group; andwhen R.sup.1 represents a methyl group, R.sup.2 represents an isobutyl group and, when R.sup.1 represents an ethyl group, R.sup.2 represents a pentyl group] have antibacterial activity which is particularly pronounced against bacteria of the genus Mycobacterium. The compounds in which R represents and N-(.alpha.-ketobutyryl)-N-methylvalyl group, named Mycoplanecin B (R.sup.1 represents a methyl group) and Mycoplanecin C (R.sup.1 represents an ethyl group), may be prepared by cultivation of a microorganism of the genus Actinoplanes, while the compounds where R represents an N-(.alpha.-hydroxybutyryl)-N-methylvalyl group or a hydrogen atom can be prepared by reducing the corresponding compound where R represents an N-(.alpha.