The structure of mithramycin reinvestigated.

A reinvestigation of the structure of mithramycin, the principal product of Streptomyces argillaceus ATCC 12956, is reported. The structure elucidation was carried out with mithramycin decaacetate (4) using 2D NMR methods, including TOCSY, HMBC, and HSQC experiments. The work resulted in structure 3being confirmed for mithramycin.

Use of surface markers for MR radiotherapy planning.

PURPOSE: For the precise planning of radiotherapy treatment ports, the delineation and control of their borders has to be performed with X-ray and other imaging procedures before and during the therapy. MATERIALS AND METHODS: Conventional planned therapy ports are checked with the help of MR-imaging with new gel-markers, as a further development to formerly used fluid filled tubes, on the skin of the patient in different regions. We describe the essentials of these gels and report about their first practical use. RESULTS: Principal considerations to the technique and practical applications are given with imaging examples. The essential physical qualities of the gels are introduced with separate NMR experiments. It turns out, that multiplanar MR-imaging in combination with field markers on the skin is a fast simple and useful help for the control and the improvement of treatment planning. CONCLUSION: MR-imaging with gel-markers on the skin in many cases can show the tumor and the field-ports in one picture. Thus the therapy planning is refined with simple means. On the one hand the target volume can be seized completely and on the other hand sensitive organs can better be protected.

5-hydroxyquinoline-2-carboxylic Acid, a dead-end metabolite from the bacterial oxidation of 5-aminonaphthalene-2-sulfonic Acid.

5-Aminonaphthalene-2-sulfonate (5A2NS) is converted by strain BN6 into 5-hydroxyquinoline-2-carboxylate (5H2QC). The authenticity of this new compound is confirmed by nuclear magnetic resonance and mass spectrometry. Its formation is explained by a spontaneous cyclization of the hypothetical metabolite 6'-amino-2'-hydroxybenzalpyruvate. The formation of 5H2QC as a dead-end product of 5A2NS prevents NADH regeneration so that 5A2NS oxidation is limited by the internal NADH pool.

Isolation and structural elucidation of naphthomycins B and C.

Two new ansamycin antibiotics, the naphthomycins B and C, were isolated from two different strains of Streptomyces. The structures were determined by comparison of the spectra (UV, 1H NMR, 13C NMR) with those of the known naphthomycin A, by spin decoupling experiments (300 MHz) and in one case by a two dimensional NMR analysis. Naphthomycin B (II) is 30-chloronaphthomycin C. Strikingly, naphthomycin A (I) differs from B and C not only by the presence of an additional methyl group at C (2), but also in the configuration of some of the double bonds. A fourth ansamycin antibiotic of the naphthomycin subgroup, actamycin, is 30-hydroxynaphthomycin C.