During the screening program for new antibacterial agents produced by actinomycetes, GE23077 was isolated from fermentation broths of an Actinomadura sp. strain as a complex of factors A1, A2, B1, B2.NMR, MS and GC/MS analysis carried out on the isolated components led to the conclusion that GE23077 is a novel cyclic heptapeptide consisting of common and unusual amino acids. The chemical structures of the complex components were elucidated.Components A and B differ in the structure of the acyl group connected to a 2,3-diaminopropanoic acid moiety. A α-amino-malonic acid residue in the peptidic sequence is the origin of an isomerization process between A1 and A2 as well as B1 and B2. The chirality of the α-amino-malonic acid residue can be inverted easily via keto-enol tautomerism. Factors A2 and B2 should be considered as epimers of A1 and B1 respectively.By degradation studies the absolute configuration of some amino acids were determined. Chiral GC-MS and Micellar Electrokinetic Capillary Chromatography (MEKC) were used to define the absolute stereochemistries of five out of ten chiral centers.

AbstractFor Abstract see ChemInform Abstract in Full Text.

GE 23077 factors A1, A2, B1 and B2 are novel antibiotics isolated from fermentation broths of an Actinomadura sp. strain. GE23077 antibiotics are cyclic peptides, which inhibit Escherichia coli RNA polymerase at nM concentrations. Both rifampicin-sensitive and rifampicin-resistant polymerases are inhibited, whereas E. coli DNA polymerase and wheat germ RNA polymerase are substantially not affected. In spite of the potent activity on the enzyme, the antibiotics generally show poor activity against whole cell bacteria. The spectrum of activity is restricted to Moraxella catarrhalis, including clinical isolates, with partial activity against Neisseria gonorrhoeae and Mycobacterium smegmatis.

AbstractFor Abstract see ChemInform Abstract in Full Text.

AbstractReaction of the anion of the sulfoxide (I) with a series of chiral but racemic aldehydes (II) yields the isomeric addition products (III) and (IV).

Dihydroquinidine acetate promoted osmylation of acetals of E-α,β- unsaturated aldehydes occurs with up to 40:1 stereoselection to afford the corresponding protected syn-α,β -dihydroxy aldehydes.

AbstractThe sulfoxide (I) is efficiently used as a synthon for the insertion of an allylic alcohol moiety into the title aldehydes (II).

Reaction of allyl sulphinyl anion with chiral α-methylaldehydes affords α- or γ-adducts in highly regio-controlled fashion, depending on reaction conditions. From the α-adducts syn (E)-2-alkene-1,4-diols are obtained as major (d.r. 2:1 ~ 28:1) products by thiophile promoted desulphurization.

Tandem condensation of chiral α -alkoxy and α,β-dial-koxy aldehydes with allylic sulphinyl anion, and thiophile promoted desulphurization of the resulting α-substituted allylic sulphoxide afford (E)-5-alkoxy-(or 5,6-dialkoxy)-2--alkene-1, 4-diols, advanced polyols precursors, the major stereochemical path occuring via a Felkin-Ahn (non chelation control) mode.