Antibiotic properties

Ring substituents show enhanced reactivity towards nucleophilic substitution, relative to the unoxidized systems, with substituents a to the fV-oxide showing greater reactivity than those in the /3-position. In the case of quinoxalines and phenazines the degree of labilization of a given substituent is dependent on whether the intermediate addition complex is stabilized by mesomeric interactions and this is easily predicted from valence bond considerations. 2-Chloropyrazine 1-oxide is readily converted into 2-hydroxypyrazine 1-oxide (l-hydroxy-2(l//)-pyrazinone) (55) on treatment with dilute aqueous sodium hydroxide (63G339), whereas both 2,3-dichloropyrazine and 3-chloropyrazine 1-oxide are stable under these conditions. This reaction is of particular importance in the preparation of pyrazine-based hydroxamic acids which have antibiotic properties. 

A range of thiolactones was obtained by virtual screening with the rationale to be covalently cleaved by FabDSer92. Among them, 4 was described as a potent E. coli FabD inhibitor with antibiotic properties although no further biological data was provided [12]. 

Condensation of coumaric acid with malonic acid yields the basic chalcone and stilbane skeletons (see Fig. 3.6). Stilbenes are found in most vascular plants, where they exhibit fungicidal and to a lesser extent antibiotic properties. They function as both constitutive and inducible defense substances. Some stilbenes inhibit fungal spore germination and hyphal growth, whereas others are toxic to insects and parasitic nematodes (round-worms). They also possess antifeeding and nematicide properties in mammals. For example, resveratrol (a stilbene in red wine) suppresses tumor formation in mammals. 

Fluorinated amino acid with antibiotic property 195, 196... 

V OH OH isoiated from Norcardia species Siderocheiin A - iron cheiator with antibiotic property 242... 

Neomycin Neomycin is a complex mixture of antibiotics (neomycins A, B, C, D, E, and F), that is formed by the actinomycete S. fradiae. Neomycin A, also called neamine, is 2-deoxy-4-0-(2,6-diamino-2,6-dideoxy-a-D-glucopyranosyl)-D-streptamine (32.4.2), and it does not display antibiotic properties. At the same time, neomycin B, 0-2,6-diamino-2,6-dideoxy-a-D-glucopyranosyl(l— 4)-0-[0-2,6-diamino-2,6-dideeoxy-)3-L-idopyra-nosyl-(l—>3)-)3-D-ribofuranosyl-(l— 5)]-2-deoxy-D-streptamine (32.4.3), differs from neomycin A in the presence a second glycoside residue and exhibits powerful antibacterial... 

Zbierska, J. and Kowalewski, Z. 1979. Anticancer and antibiotic properties of chelidonine methyliodide. Herba Polonica, 25 209-217. 

Towers, G.H.N. et al.. Antibiotic properties of thiarubrine A, a naturally occurring dithiacyclo-hexadiene polyine, Planta Med., 51, 225, 1985... 

The compounds obtained by the replacement of ring sulfur by carbon, as in the case of penicillins, show somewhat improved antibiotic properties. A free radical— based route has been described for the conversion of fermentation derived cephalosporins to their carbocyclic derivatives. The first step in this sequence consists of the condensation of the cephalosporin sulfone (36-1) with formaldehyde and dimethyla-mine the initial product from the Mannich-like reaction consists of the exomethylene derivative at the position adjacent to the activating sulfone. The product is treated in situ with phenylselenol to give the Michael adduct (36-2). This fragments with an extmsion of sulfur dioxide when heated with the free radical initiator AIBN in the presence of tributyltin hydride the reaction can be envisaged as leading to the... 

Lactone structures have recently been determined for two microbial metabolites which have antibiotic properties. Antibiotic 1233A (77) was the first /8-lactone to be isolated from a fungus. Esterastin (78), an inhibitor of esterase, is produced by a strain of Streptomyces (71JCS(C)3888, 78MI51300). 

Structure of a Peptide Antibiotic from Bacillus brevis Extracts from the bacterium Bacillus brevis contain a peptide with antibiotic properties. This peptide forms complexes with metal ions and apparently disrupts ion transport across the cell membranes of other bacterial species, killing them. The structure of the peptide has been determined from the following observations. 

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