Tabtoxins

Table wines, 26 300 fermentation of, 26 313 higher-sweetness, 26 315 Tablet press drug dosage form, 16 705-706 Tabtoxin, 15 299... 

Both compounds inhibit glutamine synthetase, which is necessary for the production of glutamine and for ammonia detoxification. Plants that are exposed to glufosinate have reduced glutamine and increased ammonia levels in their tissues, which stops photosynthesis and results in death within a few days. Other natural products (e.g. tabtoxine- -lactam, oxetin, and methionine sufoximine) are known to have this mode of action, but they have not been developed as commercial products. 

The bacteria Pseudomonas spp. produce tabtoxin and pyocyanine, alkaloids with a relatively powerful biological activity. 

Tabtoxin J is a dipeptide exotoxin produced by Pseudomonas tabaci, the organism responsible for the wildfire disease of tobacco plants [141]. When hydrolyzed by peptidase, in vivo, this exotoxin releases tabtoxinine-p-lactam K, which inhibits Glutamine synthetase of the photorespiratory nitrogen cycle, causing chlorosis and death of tobacco plants [142]. 

Some plant pathogenic bacteria and their phytotoxins have been screened in bioassays that monitor the effects of their toxins (antibiotic and phytotoxic) on other sensitive bacteria. For example, several fluorescent Pseudomonas syringae pvs. produce extracellular phytotoxins.76,106,116 Tabtoxin is produced by P. syringae pv. tabaci and pv. coronafacines, and this natural product inhibits glutamine synthetase.34,46,116 Phaseolotoxin, produced by P. syringae pv. phaseolicola... 

Turner, J. G. and Taha, R. R. 1984. Contribution of tabtoxin to the pathogenicity of Pseudomonas syringae pv. tabaci. Physiol. Plant Pathol. 25, 55-69... 

The nucleophile in the side chain will attack the carbonyl group of the lactam and, in the course of the ring enlargement, the atom 1 acts as an internal leaving group. The first example in Scheme VI/19 is tabtoxin (VI/90). 

This compound undergoes a translactamization reaction to give the non-toxic isotabtoxin (VI/91) at room temperature and neutral pH with a half-life of about one day [77] [78] [79]. Inactivation of tabtoxin is even quicker in either acid or base [80]. (The driving force of this conversion seems to be the change to a less strained molecule). The transformation of the /1-lactam to the five-mem-bered VI/95 (by heating in anisol) is another example of this type and includes... 

Tabtoxin. The phytotoxic compound tabtoxin [77] Is excreted by Pseudomonas svrinaae sp. taba l> as well as other strains, and Is... 

Af-Benzyloxycarbonylhydroxylamine has also been employed in the [4 + 2] cycloaddition to methyl 1,3-cyclohexadiene-l-carboxylate or -carbonitrile in a total synthesis of tabtoxin. The reaction afforded a single diastereomer 10 in good yield, and the structure was assigned by H NMR and confirmed by chemical transformations61-64. 

Baldwin and co-workers have used a nitroso Diels-Alder reaction as a key step in total synthesis of tabtoxin (17), a metabolite causing leafspot disease in tobacco.41 This group has also prepared tabtoxinine /3-lactam (18), the active principle generated by in vivo enzymatic hydrolysis of 17. 

Threonine, A/-[2-amino-4-(3-hydroxy-2-oxo-3-azetidinyI)-1-oxobutyl]- tabtoxin ... 

Tabtoxin is an exotoxin of the phytopathogenic bacterium Pseudomonas tabaci, first isolated in 1952, and induces the wildfire disease, a leaf-spot disease, on tobacco plants [41]. The structure of tabtoxin 27 was reported almost 20 years later [42],... 

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