2-14C Acetate

Garson, M. J., Biosynthesis of the novel diterpene isonitrile diisocyanoadociane by a marine sponge of the Amphimedon genus incorporation studies with [14C]cyanide and sodium [2-14C]acetate, J. Chem. Soc. Chem. Commun., 35, 1986. 

In experiments with intact plants, the activity from [l-14C]acetate was found to be incorporated specifically into the predicted position for each alkaloid. In parallel experiments with [2-14C]acetate, iV-methylpelletierine was degraded and shown to have, as expected, 50% of the activity located in the C-methyl group. The sequence of intermediates in the late stages of the pathway were investigated with the following results (i) iV-methylpelletierine (90) is incorporated into pseudopelletierine (91), and (ii) pelletierine (89) is a precursor of anaferine (92). 

The alkaloid (93) which is produced by Haloxylon salicornicum shows a structural resemblance to pelletierine (89). A feeding experiment58 with [6-14C]-lysine in intact plants has supported the related biosynthesis in Scheme 18. Activity was incorporated at C(6) of the alkaloid as shown. Surprisingly, no activity was incorporated from [2-14C]acetate but this negative result could be due to the failure of acetate to reach the site of synthesis. 

Fig. 3. Incorporation of 2-14c-acetate into fatty acids and molecular species of DGTS.

Fig.2 [2-14C]acetate incorporation into the total fatty acid fraction of chloroplasts isolated from different sensitive and tolerant plants in addition of IpM sethoxydim. The incorporation rates of the controls in nmol acetate (mg chlorophyll h)" were 32 for Avena sativa, 38 for Pisum sativum, 4 for Poa pratensis and 6 for Poa annua. Mean values of 4 determinations with SD. 

Nephroma laevigatum from British Columbia contained the following anthraquinones emodin, 7-chloroemodin, 7-chloro-l-O-methylemodin, 7-chloro-1 -0-methylcitreorosein, 5-chloroemodin, 5-chloro-l-O-methyl-emodin, 5-chloro-l-O-methylcitreorosein and 5-chlorocitreorosein. Feeding experiments with Na[2-14C]-acetate and Na[l-13C]-acetate showed that these anthraquinones are biosynthesized via the polyketide pathway (75). 

In more recent studies the use of HPLC allowed isolation and counting of individual sterols after administration of labelled precursors. The sterols isolated from mantles and viscera of the nudibranch Doris verrucosa were identified as cholestanol, cholesterol, 24-dehydrocholesterol and 7-dehydrocholesterol [103]. After injection of dl-[2-14C]-mevalonic acid DBED salt, cholesterol (57) and 7-dehydrocholesterol (58) were isolated as the acetates by reversed phase HPLC. Both sterols were found significantly labelled specific radioactivity associated with 7-dehydrocholesterol was higher by one order of magnitude than that associated with cholesterol. This fact would indicate either that the reduction of the A1 double bond of 7-dehydrocholesterol to afford cholesterol occurs at a low rate, or that the cholesterol found in D. verrucosa comes partly from a dietary source. 

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. 

Another convenient method for the preparation of functionalized cyclobutanol derivatives is by treatment of 1,2-diphenylethylene acetals containing a 1,3-dithiane moiety in the y-position, e.g. 14c. with butyllithium. The isolation of 2,2-(propane-l,3-diyldisulfanyl)cyclobutanol (15c) together with benzyl phenyl ketone in 90 and 92 % yield, respectively, indicates that the reaction mechanism should involve the intramolecular attack of the metalated dithiane on the acetal carbon atom with concomitant hydride shift at the acetal group.15... 

The position of a single labeled atom in a molecule is shown following the chemical name of the compound. Thus, acetic-l-14C acid is CH COOH, whereas acetic-2-14C acid is 14CH3COOH. 

The red algal chamigrene sesquiterpene elatol (Structure 2.78) has been shown to deter feeding by reef fishes.93 Specimens of Laurencia elata from Southern Australia show a pronounced seasonal variation in elatol production. Incorporation studies using 14C acetate failed to confirm an acetate-mevalonate path for elatol production.125... 

Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins, which had been previously treated with juvenile hormone III (JH III, 2.2 pg/beetle in acetone) and then placed in an aeration tube for 25 to 30 h. Ips paraconfusus and I. pini were each injected with 0.2 pCi of sodium [1-14C]acetate prior to placement in cut pine logs and volatile collection, while D. jeffreyi were each injected with 3.8 (male) and 3.7 (female) pCi of sodium [1-14C]acetate 6.4 (male) and 10.7 (female) h after JH application. (G) The role of the mevalonate pathway in frontalin biosynthesis is supported by the incorporation of radiolabel from [2-14C]mevalonolactone into frontalin by male D. jeffreyi (2.2 pg JH 11 l/beetle in acetone, 10 h incubation and volatile collection, 1.1 pCi of [2 14C] mevalonolactone injected, 20 h volatile collection). Figures adapted from Seybold et al. (1995b) and Barkawi (2002). 

When [2-14C]phenylalanine was administered to Decodon plants about two-thirds of the activity of decodine and decinine was located at C-2. This carbon was isolated as the a-naphthylamide of acetic acid by the Kuhn-Roth oxidation of the -propyl derivative. 

Skiba, P. J. and Jackson, L.L. (1993). (Z)-10-Heptadecen-2-one and 2-tridecanone biosynthesis from [l-14C]acetate by Drosophila buzzatii. Insect Biochem. Mol. 

The biosynthesis of virginiamycin Ml in Streptomyces virginiae has been studied using both radiolabeled precursors (63) and stable isotope techniques (45, 63-65). Incorporation of [2-l4C]acetate, L-[methyl-3H]methionine, dl-3-14C]serine, L-[3,4-3H2]proline, and [2-14C]glycine established these compounds as the main precursors (63). The assumption that carbons 2, 26, 27, and 28 arose from valine was supported by the observation that no incorporation of appropriately labeled mevalonolactone was observed (65). On the basis of the radio-... 

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