Abstract
IN 1947, Ehrensvard suggested the use of a new protective group for peptide synthesis1. According to his investigations, the phenylthiocarbonyl grouping (C6H5—S—C—O—) can be used advantageously for the protection of the amino-groups of amino-acids. The phenylthiocarbonyl-group could be split off from the N-phonylthiocarbonyl -peptide derivatives by means of lead acetate. Lindenmann, Khan and Hofmann2 confirmed Ehrensvard's observations ; but according to their investigations hydantoins, not peptides, resulted under the influence of lead acetate. As no method was given for splitting off the phenylthiocarbonyl-group, we attempted the application of oxidative methods, and with complete success. The oxidation is carried out with 2.5 moles of perbenzoic acid at − 5° in acetic acid – benzene, benzene – tetra hydrofurane, dioxane or dioxane containing preferably 2 per cent of water. The products of oxidation probably represent a type of mixed anhydrides of carbamic acids with sulphinic acids hitherto unknown:
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