The constitution of ergothioneine : a betaine related to histidine / by George Barger and Arthur James Ewins.

  • George Barger
Date:
[between 1910 and 1919?]
Catalogue details

Licence: In copyright

Credit: The constitution of ergothioneine : a betaine related to histidine / by George Barger and Arthur James Ewins. Source: Wellcome Collection.

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    trimethylamine and a yellow acid of the composition C6n602N2S, which represents the whole of the remaining atoms in the molecule, and the constitution of which is represented by (II). On boiling with dilute nitric acid, the sulphur atom of this acid is completely removed, and a new acid, /3-glyoxaline-4(or 5)-acrylic acid (III), is formed. This acid on reduction yields /3-glyoxaline-4(or 5)-propionic acid (IV), and we were able to identify both the saturated and the unsaturated acid by comparison with synthetic specimens. The various reactions will be best seen from the following scheme : CH-ISIH, 11 C- CHf -N >CH CH-NEL „ T CH*NH. ari .NH-CH b-n>C-SH -n>CS-SC^n„h CH*NMe„ i i 2 co-o (VI.) FeClg <— CII2 CH-NMe, i i £ co-o (I.) CH2 h2c -T-> CH-NMeJ IMe,N-HC co2h H02C (V.) yKOH §™>C-SH OH 11 CH C HNO3 -> co2h CH 11 CH C02H -w Na+alcohol --^ (II.) (HI.) CH-NH. nxj ch2 9H2 co2h (IV.) The only doubtful point remaining was with regard to the position of the sulphur atom. There are two probable positions, namely, attachment to the j6-carbon atom of the side-chain or to the carbon atom in the 2-position in the glyoxaline ring, and choice between these two, although decisive, is based on analogy rather than on direct evidence; indeed, synthesis seems to be the only means of supplying complete proof. The sulphur in ergothioneine reacts in every way like that of the thiolglyoxalines, and quite different from that in cystein, with which it might be expected to show analogies if attached to the /3-carbon atom of the side-chain; thus the sulphur in cystein, as is well known, is readily eliminated by boiling with sodium hydroxide, whereas, as was stated above, the sulphur of ergothioneine is not removed by boiling with the strongest solutions of potassium h}^droxide. On the other hand, the sulphur atom, like that of the thiolglyoxalines, is readily and quantitatively oxidised by ferric chloride (as recently employed by Pyman) or by bromine water to sulphuric acid, whereas in the case of cystein a sulphonic acid results, in which the sulphur still remains attached to the carbon atom. The only oxidising agent which acts similarly on cystein and ergo-
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