Experiments on the formation of 4(or 5)-L-aminoethylglyoxaline from histidine / by Arthur James Ewins and Frank Lee Pyman.

  • Ewins, Arthur James.
Date:
[1911?]
Catalogue details

Licence: In copyright

Credit: Experiments on the formation of 4(or 5)-L-aminoethylglyoxaline from histidine / by Arthur James Ewins and Frank Lee Pyman. Source: Wellcome Collection.

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    of our investigation was therefore to endeavour to find a simple method of obtaining the base directly from histidine, which is comparatively easily obtainable. In this we were only partly suc¬ cessful, since we were able to obtain only moderate yields of the base by the action of acids in sealed tubes at a temperature of from 265° to 270°. This last factor (temperature) made it a matter of very great difficulty to obtain anything like large amounts of the base. The results obtained, however, were deemed of sufficient interest to form the subject of the present communication. Experiments were first carried out to determine whether, as in the case of the formation of p-hydroxyphenylethylamine from tyrosine, carbon dioxide could be removed from histidine by direct heating. It was found, however, that under varying conditions only a very small amount (0'3 to 1*0 per cent) of base could be obtained, and the method was abandoned. By directly heating the monobenzoyi derivative of histidine and subsequently hydrolysing, a somewhat better yield (10 to 20 per cent.) of the base was obtained. The effect of various acids under varying conditions of tem¬ perature and concentration was then investigated, and it was found that yields of base amounting to about 25 per cent, of the theoretical could be obtained with concentrated hydrochloric acid, moderately dilute sulphuric acid, and fused potassium hydrogen sulphate under suitable conditions. After heating for three hours with acids at temperatures below 240°, no formation of 4(or 5)-j8-aminoethyl- glyoxaline took place. At about 240° very little of the base was obtained, the main product of the reaction being r-histidine, which had previously been prepared by Frankel (Bditr. Chem. Pliy&iol. Path., 1906, 8, 156) in a similar manner. As the temperature was raised, the yield of base gradually improved, and reached a maximum (about 25 per cent, of the theoretical) at about 265—270°. Further increase of temperature led to diminished yield of 4 (or 5)-j8-aminoethylglyoxaline. With phosphoric acid (44 per cent.) at 250°, no base was produced, nor did the use of hydrogen bromide in acetic acid solution at somewhat lower temperatures yield any better results. The progress of the work was very greatly facilitated by the physiological estimation of the yield of base in many of our experi¬ ments. This was kindly undertaken for us by Dr. H. H. Dale and Dr. P. P. Laidlaw, to whom we wish to express our indebtedness and thanks. During the course of the investigation some hitherto undescribed salts of histidine and 4(or 5)-/3-aminoethylglyoxaline were prepared, and are now described.