The isolation of some hitherto undescribed products of hydrolysis of proteins.— Part III

Abstract

The recent discoveries of hydroxylysine, hydroxyvaline, and hydroxyaminobutyric acid, described in the earlier papers of this series, together with the discovery a few years earlier of hydroxyglutamic acid by Dakin, lead to the conception that there is to be found among the hydrolysis products of the proteins a hydroxyl derivative corresponding to every (or nearly every) nonhydroxyamino-acid that has been isolated. Yet, so far, the hydroxyl derivative of leucine, perhaps the most widely distributed hydrolysis product of the proteins, has not been discovered. In searching for such a substance, certain possibilities of chemical change must be taken into account. It is known that in the presence of hot solutions of strong acids, such as the 25 per cent. sulphuric acid used for the hydrolysis of proteins, hydroxy derivatives of long-chain substances tend to undergo isomeric change, with the wandering of the hydroxyl group from one position to another. Supposing, now, that hydroxyleucine exists among the hydrolysis products of proteins, and that the hydroxyl group is in the β position,