Tritium-Labeled Compounds XII. Note on the Synthesis of d-Glucose-2-t and d-Mannose-2-t

d-Glucose-2-t and d-mannose-2-t have been synthesized from sodium 2-keto-d-gluconate (sodium d-arabino-hexulosonate). Reduction of the salt with lithium borohydride-t produced the epimeric, 2-labeled aldonic acids in almost equal proportions. The acids, separated by carrier techniques, were lactonized, and the lactones were reduced with sodium amalgam to the corresponding sugars. The specificity of the labeling was established by converting each sugar into d-arabino-hexulose phenylosazone and determining that the osazone was substantially tritium-free.