Levulinic acid, labeled

A rapid synthesis of carbon-14 labeled [l-14C]levulinic acid from simple building blocks has been demonstrated by Johansen and coworkers (Scheme 6.172) [324], In all three of the synthetic steps, starting from bromo[l-14C]acetic acid, microwave heating was used to accelerate the reactions, allowing a total preparation time of less than 1 h. The labeled levulinic acid was subsequently transformed into (5Z)-4-bromo-5-(bromomethylene)-2(5H)-furanone in a bromination/oxidation sequence (not shown), a potent quorum sensing inhibitor. 

The ethynyl-7-lactone (XI), prepared from levulinic acid as indicated in Fig. 7, was partially tritiated to give the labeled vinyl-7-lactone (XII). 

Shemin and RusselF have recently found that labeled 5-amino levulinic acid is converted to heme at a faster rate than are either labeled succinic acid or glycine. They suggest that two molecules of 6-amino levulinic acid condense to form the first pyrrole, porphobilinogen (Fig. 4). 

Reactions with functionalized alkyl halides significantly enhance the range of application of alkyl [ C]acetoacetates. Alkylation of ethyl [3- C]acetoacetate with halo esters, for example, followed by acid-mediated ketonic cleavage opens access to labeled keto acids/esters, as demonstrated by the synthesis of the [4- C]levulinic acid (307) a y-keto acid. The latter has served as a key intermediate in the synthesis of the 2,3-substituted indole 308 . Step 2 in Figure 6.85, the ketonic cleavage, has recently been shown to be accelerated by a factor of 20 when the reaction is submitted to microwave heating. ... 

Membrane composition and biosynthesis. Fig. 3 shows an autoradiographic profile of a 10-20% polyacrylamide gel. Cells grown in complete media were harvested and inhibited by 140 mM levulinic acid. S-sulfate (50 yCi/ml) was added after 6 hr, and the cells were illuminated for an additional 3 hr. Membranes were prepared as described. Fig. 3 shows the label incorporation patterns for membranes of uninhibited (lane A) and levulinic acid-treated (lane B) cells. Inhibition caused a set of changes in the biosynthetic pattern. For example, decreased label was observed in the biliproteins (15 and 19 kDa). Decreased label also occurred at 71 kDa. Three prominent changes are shown by arrows in Fig. 3, and the results of several experiments are summarized in Table I. Decreased incorporation was observed at 11 polypeptide bands, while 3 bands showed... 

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