Bettina Böhlendorf

Pedein A and B: Production, Isolation, Structure Elucidation and Biological Properties of New Antifungal Cyclopeptides from Chondromyces pediculatus (Myxobacteria)

AbstractTwo new secondary metabolites, named pedein A and B, were isolated from the cell mass of the myxobacterium Chondromyces pediculatus. Their planar structures were elucidated by spectroscopic methods, in particular 2D NMR as 24-membered cyclic hexapeptides composed of a variable tryptophan residue, glycine, sarcosine and three unusual hydroxy β- and γ-amino acids. The main component, pedein A, strongly inhibited the growth of yeasts and fungi, induced hemolysis of erythrocytes, and caused changes in membrane permeability of Rhodotorula glutinis. The structures of the pedeins are closely related to the large family of the microsclerodermins, which have been isolated from lithistid sponges of Microscleroderma and Theonella species.

Structure Determination of Neoefrapeptins A to N: Peptides with Insecticidal Activity Produced by the Fungus Geotrichum candidum

The structures of neoefrapeptins A to N, peptides with insecticidal activity, were elucidated. They showed a close similarity to efrapeptin. However, all neoefrapeptins contained the very rare amino acid 1-amino-cyclopropane-carboxylic acid and some of them also contained (2S,3S)-3-methylproline. The neoefrapeptins are the first case, in which these amino acids are found as building blocks for linear peptides. They were identified by comparison of the silylated hydrolyzate to reference material by GC/MS (EI-mode). The sequence was elucidated using mass spectrometry (ESI+ mode). Full scan spectra showed two fragments in high yield, even under mild ionization conditions. MS/MS spectra of these two fragments yielded fragment rich spectra from which the sequence of the compounds was determined almost completely. The proteolytic cleavage with the proteinase papain yielded products that allowed to prove the rest of the sequence and the identity of the C-terminus to efrapeptin. The proteolytic cleavage products allowed furthermore to determine the position of the isobaric amino acids, pipecolic acid and 3-methylproline in neoefrapeptin F, as well as the location of R-isovaline and S-isovaline. Papain digestion was such established as a tool for structure elucidation of peptides rich in α,α-dialkylated amino acids. CD spectra suggested a 310 helical structure for neoefrapeptins A and F.

Semisynthesis and antiplasmodial activity of the quinoline alkaloid aurachin E.

A one-step synthesis of the rare aurachin E (1) from the easily accessible aurachin C (2) and cyanogen bromide is described. 3-Bromocarbamoylquinoline (5) is formed in a side reaction with concomitant loss of the 3-farnesyl residue. In an alternative approach, aurachin D (3) was reacted with phosgene and sodium azide to form the imidazolone ring of 1 via N-acylation. Unexpectedly, the initial reaction occurred at the carbonyl group of 3 to give 1H-pyrrolo[3,2-c]quinoline 4. The reaction sequence represents a novel route to this type of compound. Aurachin E, contrary to other aurachins, combines a high in vitro antiplasmodial activity with low cytotoxicity and absence of mitochondrial respiratory inhibition.

Maracin and Maracen: New Types of Ethynyl Vinyl Ether andα-Chloro Divinyl Ether Antibiotics fromSorangium cellulosum with Specific Activity Against Mycobacteria

Like something originating from the chemistry laboratory rather than from Nature: However, the title compounds 1 and 2 are, in fact, synthesized by myxobacteria of the species Sorangium cellulosum according to the same assembly pattern from acetate and are excreted into the culture medium. Both compounds have remarkably good in vitro activity against the pathogen responsible for tuberculosis, Mycobacterium tuberculosis.