Studies on secondary metabolites produced by actinomycetes and cyanobacteria

iosynthetic studies compounds showed that the Adda unit of nodularin was derived from C-2, C-3 and the phenyl ring of scL-phenylalanine as well as acetate and methionine. A separate feeding experiment with (2-;An acyclic nodularin, N-842, was isolated from the cultured Nodularia spumigena and its structure was assigned as Adda- scD-Glu-Mdhb- scD-MeAsp- scL-Arg-OH. Isolation of nodularin and N-842 from a continuously cultured batch suggested that N-842 is a biogenetic precursor to nodularin. Based on these findings, biogenetic pathways of nodularin and the structurally related compound, microcystin-LR, are proposed.;Dihydro derivatives of nodularin and microcystin-LR were prepared by sodium borohydride reduction of the dehydroamino acid residues. The stereochemistry of each reduced amino acid was obtained by acid hydrolysis of dihydro derivatives followed by GC analysis of their trifluoroacetyl methyl ester derivatives. Deuterated derivatives were prepared in an analogous manner using sodium borodeuteride.;Analysis of FABMS/MS spectra of the linear peptides, which were obtained from ozonolysis followed by sodium borohydride reduction and acid treatment of microcystins, allowed elucidation of the sequence of the microcystins.;The fate of the dihydromicrocystin-LR's in pigs was studied by isolating the radioactive metabolites from tritiated dihydromicrocystin-LR injected pigs. Greater than 90% of the radioactive material from the liver proved to be the parent toxins. The remaining radioactivity was attributed to several unidentified metabolites.;Unlabeled 4,5,6-tri-O-benzylvalienamine was synthesized from methyl ;The...