Aus den Zellen von Myxococcus xanthus Mx x12 (GBF) wurde ein neuer Antibiotika‐Komplex, genannt Myxalamide, isoliert. Nach Vorreinigung an Florisil wurden die myxalamide durch chromatographie an einer Umkehrphase in vier Komponenten aufgetrennt. Die spektroskopische Untersuchung der Hauptkomponente, Myxalamid B (1), ergibt die Struktur eines Alaninolamids mit einer verzweigten, hohungesättigten Fettsäure. Die Myxalamide A (3), C(4) und D(5) sind Amide aus homologen Fettsäuren und Alaninol.
The natural abundance I3C n.m.r. spectra of six bile pigments and several related compounds are reported. Two of the former, namely mesobiliverdin-lXa dimethyl ester (1 1 ) and mesobilirubin-lXx dimethyl ester (1 6), were specifically 13C-enriched at several positions in the molecule, which allowed the complete assignment of their quaternary pyrrolic carbon signals and thus aided in the assignment of the latter in the other bile pigments. Substituent changes in the pyrromethen-5(1 H ) -one model compounds give rise to 13C chemical shift changes indicative of considerable delocalisation over the entire conjugative system. The shifts for the bile pigments indicate that the lactam is the preferred tautomeric form in all cases. The magnitudes of the large number of one-bond carboncarbon spin-spin coupling constants for the enriched compounds correlate with bond lengths derived from crystallographic studies of similar compounds and with the relative percentage of s-character of the carbon-carbon bond involved in the coupling. Consequently the extent of bond delocalisation in (1 1 ) and (1 6) was deduced, and for (1 1) it is shown to be higher over rings II and Ill than over rings I and II, or over rings Ill and IV.
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