Tritium-Labeled Compounds III. Aldoses-1-t

In a new method for preparing aldoses labeled with tritium at carbon 1, the aldonic lactone is reduced with lithium borohydride-t in pyridine solution. The method is suitable for preparing aldoses-1-t having high specific activities. The crude product contains a substantial proportion of the corresponding alditol-1-t, but the pure aldose-1-t is readily separated by fractional recrystallization or paper chromotography. By means of an isotope-dilution technique, yields were determined for the following aldoses-1-t and the corresponding alditols-1-t: d-arabinose-1-t, d-xylose-1-t, d-ribose-1-t, d-glucose-1-t, d-galactose-1-t, d-mannose-1-t, l-rhamnose-1-t, maltose-1-t, and lactose-1-t. These labeled materials were also prepared by reducing the corresponding lactones with sodium amalgam in tritiated water. Although this latter method is not suitable for preparing labeled aldoses of high specific activity, the products are more readily purified than those obtained by reducing the lactones with lithium borohydride-t. d-Glucose-1-t, obtained by each of these reduction methods, was oxidized with bromine, and the resulting d-gluconic acid was found to be nonradioactive. Hence, in the samples oxidized, tritium was present only at C1. An apparatus used tor reclaiming tritiated water by freeze-drying is depicted; it incorporates an efficient device for trapping entrained solids or liquids.