Structure of thioviridamide, a novel apoptosis inducer from Streptomyces olivoviridis

A novel apoptosis inducer, thioviridamide, was isolated from an actinomycete identified as Streptomyces olivoviridis. The molecular formula of thioviridamide was determined to be C56H93N14O10S7+ from high-resolution FAB-MS. The structure of thioviridamide was analyzed by NMR spectral analysis including a variety of two-dimensional techniques. COSY and HMBC experiments revealed the presence of a 2-hydroxy-2-methyl-4-oxopentanoyl group and eleven amino acid residues including two novel amino acids, beta-hydroxy-N1,N3-dimethylhistidinium and S-(2-aminovinyl)cysteine. 1H-13C long-range correlations observed in the HMBC, CT-HMBC and HMBC-HOHAHA spectra connected the partial structures with seven amide linkages and five thioamide linkages to establish the planar structure of thioviridamide as a unique cyclic peptide.