Primary and secondary hydroxyl groups can be replaced by deuterium or tritium when the corresponding sulfonate esters are reduced with zinc, sodium iodide, and deuterium or tritium oxide in 1,2-dimethoxyethane. The method tolerates a variety of other reducible functionalities, namely, ,/3-enone, ketone, and ester. The labeling can be conducted with a high regiospecificity in the presence of enolizable hydrogens. The method is less satisfactory for a stereospecific replacement of secondary hydroxyl groups, yielding mixtures of stereoisomers and olefins as byproducts. The distribution of the stereoisomers depends on the rate of configurational inversion in the intermediary iodides arising by displacement of the original tosyloxy group. Deuterium NMR spectra and their use in the configurational assignment are discussed.
SUMMARY
On hydrogenation of the 2,6-bis(phenylhydrazone) of 2,6-diketopimelic acid with carrierfree tritium a very low specijic activity2,6-Diaminopimelic acid (DAP) is the construction unit of peptides of the cell membranes of microorganisms. In our previous communication (l) we described the preparation of 2,6-diaminopimelic-2-14C acid. For autoradiographic investigation of the localization of DAP in cell tissues, tritium-labelled DAP is more suitable; the preparation of DAP of high specific activity was not described so far. We tried first to introduce tritium by hydrogenation of the double bonds in the 2,6-bis(phenylhydrazone) of 2,6-diketopimelic acid.From 2,6-diketopimelic acid I (Cope and Fournier) ( , ) we prepared its bis(pheny1hydrazone) 11 and we hydrogenated it with carrier-free tritium. Hydrogenation took place most rapidly on PtO, (Adams catalyst) in ethyl acetate. After the consumption of approx. 3 equivalents of tritium (per one eq. of phenylhydrazone 11) the hydrogenation was interrupted and the reaction (hydrogenation) was brought to completion with hydrogen. After elimination of the labile activity and purification of the product by paper chromatography, however, the specific activity of DAP was 8 mCi/mmole only. It is evident from the activity balance of the experiment that practically the total tritium in the positions 2 and 6 was exchanged under the conditions of hydrogenation (with hydrogen) to completion. During the elimination of the labile activity and subsequent chromatography practically all the activity was washed out from the product.
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