R. Synge
1948
Citations
0
Influential Citations
106
Citations
Quality indicators
Journal
The Biochemical journal
Abstract
This paper describes the'synthesis offive dipeptides required for study of thd structure of gramicidin S (Consden, Gordon, Martin & Synge, 1947). For all the syntheses carbobenzoxy derivatives were employed according to Bergmann's general procedure; coupling was effected in each case through the acid chloride. Fair yields were obtained at all stages, and no special difficulties were encountered. This appears to be the first time that peptides of valine or of ornithine have been synthesized by the carbobenzoxy procedure. For synthesizing OC-(L-valyl)-L- ornithine it was necessary to block the 8-amino group of ornithine with the carbobenzoxy radical. This was done by both the procedures that have been used for homologous preparations with lysine, i.e. (1) through the NN'-dicarbobenzoxy derivative, its acid chloride and the cyclic a-N-carboxy anhy- dride (Bergmann, Zervas & Ross, 1935); (2) through the copper complex of the free amino-acid (Neu- berger & Sanger, 1943; cf. Kurtz, 1938). Sanger (1946) has already employed the latter procedure for the preparation of 8-N-2:4-dinitrophenylornithine. Both procedures gave similar yields, but the copper method involved somewhat simpler manipulations. (methanol, Found: l, 62-5; N, N, AEW, 348. 0-18 g. was hydrogenated as described above. 0-10 g. of crystalline material resulted. A paper-strip chromatogram developed with n-butanol revealed, on colouring with nin- hydrin, a single yellow band. The material was recrystallized from water by addition of ethanol. Analysis showed the product to be L-prolyl-L-valine hydrate. The water of crystallization was lost very slowly in a vacuum desiccator at room temperature. [a] 20 610 (water, c = 1-7) (calc. for the hydrate). The air-dry hydrate was used also for the analyses. Found: C, 52-1; H, 8-5; N, 12-6; amino N (Van Slyke, 4 min. reaction time), 0-0. ClOH1803N2. H20 re- quires C, 51-7; H, 8-6; N, 12-1%; amino N, nil.