Acetic acid, labeled, degradation

If the norbornyl cation is formed on solvolysis of < xo-norbornyl derivatives, C2 should become equivalent to C and C7 to C3. In a most elegant tracer experiment, Roberts and Lee synthesized w-2-norbornyl-[2,3-14C] brosylate (85), solvolyzed it in acetic acid, and degraded the product. Equation 6.39 shows the product distribution expected if the symmetrical carbonium ion (82) were formed. The label was found not only at Cx, C2, C3, and C7, but also at C5 and... 

More than 100 years later, Comforth, Hunter, and Popjak made use of this reaction in determining the pattern of isotope distribution in cholesterol produced by biosynthesis from labeled acetic acid. One degradation liberated ring A in the form of 2-methylcyclohexanone (1), which was converted by the Schmidt reaction into the lactam (2), which in turn was converted by hydrolysis and methylation into the... 

Aminolevulinic acid (ALA), labelled with 13C at C(1). C(2), C(3), C(4) and C(5), has been synthesized64 from 13C-labelled KCN, glycine, Meldrum s acid or bromoacetate, prepared in turn from 13C-sodium acetate or 13C-acetic acid (equations 26 and 27). It was used for direct observation of the enzymatic transformation of ALA to porphobilinogen (PBG) by 13C-high-field FT-NMR spectroscopy without chemical degradation of the intermediate and the compounds. 

Measurements of the incorporation of 14C-labeled pesticides tend to support the concept of limited microbial growth from pesticide degradation. In order for a pesticide to support support substantial growth, concomitant levels of mineralization and incorporation into biomass should be observed. Studies with 14C-2,4-D, labeled in either the acetic acid or ring structures show that more 14C from the acetic acid is incorporated into biomass than from ring-labeled, depending upon soil type and the time after addition of the 14C to the soil (Table 1). Even lower amounts of carbofuran were incorporated into biomass than were observed for 2,4-D. There was not a strong relationship between mineralization and incorporation into biomass. 

Since these early studies, numerous additional procedures have been developed for the synthesis of chiral labeled acetic acid and other chiral labeled molecules by chemical (I41-15I) and enzymic methods 152-155). The malate synthase/fumarase system described above continues to be the most widely used method for the stereochemical analysis of chiral labeled acetic acid resulting from the degradation of product molecules containing chiral methyl groups. 

The fate of radioactive labels, particularly carbon, is determined by unambiguous degradation of the radioactive metabolite to isolate the labelling site from all others. Specific labelling of a particular site, or sites, indicates specific utilization of the precursor, e.g [l- " C]acetic acid 2A) specifically labels the sites indicated in orselli-nic acid (2.5), thus showing that acetic acid is specifically a source for... 

The degradation of isazofos was studied in soil samples under field and laboratory conditions. After incubation, labeled isazofos residues were extracted with acetone-methanol (1 1) and acetone-methanol-dichloromethane (1 1 1). The extracts were chromatographed on silica gel plates developed with chloroform-ethyl acetate-hexane-acetic acid (12 12 6 1). The miginal isazofos was observed at Rf 0.89 and 5-chloro-l-isopropyl-3-triazolol at Rf 0.49. The pH of the soil had a great influence on the degradation of isazofos (65b). 

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