Chemical screening of Fungi imperfecti strains resulted in the detection, isolation, and structure elucidation of a new symmetric 16-membered macrodiolide, named helmidiol (1). This secondary metabolite from Alternaria alternata (strain FH-A 6965) shows anthelmintic properties.

Methyl 2,3,6-trideoxy-3-hydroxyamino-3-C-methyl-a-D-r^(9-hexopyranoside (2) and the corresponding amino sugar (4) were isolated from reduced viriplanin A by acidic methanolysis and esterified to the di-p-bromobenzoates (3 and 5), respectively. The absolute configuration of crystalline 3 was determined by X-ray analysis to be a-D. This result could be confirmed by oxidation of 2 to methyl a-D-decilonitroside (6) and from the CDspectra of 3 and 5. Thus, the nitrogen-containing sugars of viriplanin A and probably those of decilorubicin and arugomycin belong to the D-series.In a previous paper0 we reported the isolation and characterization of viriplanin A, a new anthracycline antibiotic produced by Ampullariella regularis, and gave the first structural details of the aglycone, viriplanol, and the sugar moieties 2-deoxy-L-fucose (deFuc) and 4-0-niesaconoyl-L-dignose (MDig). In addition, we isolated a methyl /3-glycoside of the nitro sugar decilonitrose (DEC) by acidic methanolysis. This compoundshowed the same spectroscopic data as methyl /3-L-decilonitroside (1) isolated from decilorubicin2) and arugomycin3). Viriplanin A contains two sugar moieties which though similar are not identical to decilonitrose. This suggests that the isolated methyl /3-decilonitroside cannot be directly formed from the antibiotic itself. Further effort is required in order that these unknownsugars or their derivative maybe characterized.The absolute configuration of 1 was established by a comparison of the optical rotation values of methyl /3-glycoside isolated from decilorubicin with that obtained by synthesis2). Because of the fact that nitro sugars are very unstable and the yields of 1 from the natural source are very low, we decided against characterizing the configuration by the optical rotation only. The absolute configuration of the nitrogen-containing sugar derived from viriplanin A was determined independently by crystallizing a bromine containing derivative for an X-ray analysis. Wealso describe the reduction of the unknownviriplanin A sugar prior to methanolysis and the isolation and structure elucidation of the more stable hydroxyaminoand amino sugars, respectively. Hydroxyamino Sugar and Derivatives Viriplanin A was reduced under a nitrogen atmosphere by treatment with hydrazine -graphite at 55°C. The known methyl glycosides of deFuc and MDig13as well as a new nitrogen-containing sugar were liberated by treatment of the reduction product with 4 m methanolic hydrogen chloride at