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88 THE PROTEIN SUBSTANCES.
by Treat B. Johnson.1
He has prepared the following: thioglycylglycin-
thioamide NH2CH2CS.NHCH2CSNH2 which is analogous to glycylgly-
cinamide, NH2CH2CO.NHCH2CONH2 and also dithiopiperazine
.CH2.C0V
hn/ ">nh.
XCS.CH2
Polypeptides of higher amino-fatty acids such as a-aminolauryla-
lanine, a-aminolaurylleucine and others have been prepared by Hop-
wood and Weizmann.2
These peptids are different from the so-called
lipopeptids prepared by Bondi and his collaborators 3 which are not
chains of only amino-acids but combinations between a high fatty acid,
such as lauric- or palmitic acid and an amino-acid (glycocoll or alanine)
or a dipeptide (lauryl-alanylglycine)
.
Methylated polypeptides such as methyl- and dimethylleucylglycine (E..
Fischer and Gluud) and betaindiglycylglycine
(CH3) 2N. CH2CO.NHCH2CO.NHCH2CO
(Abderhalden and Kautzsch) are also known. 4
Amides of amino-acids and
dipeptides have been prepared by Bergell 5
and his co-workers.
The methods used by E. Fischer in the synthetical preparation of
polypeptides are chiefly as follows:
The first dipeptide prepared by him, glycylglycine, he obtained from glycocoll
ethyl ester which in water is transformed into a diketopiperazine, glycine anhy-
dride, according to the following equation:
/CH2 .COx
2(XH2CH2CO.O.C2H6) = 2C2H6OH+NH< >NH.
NCO.CH/
By the action of dilute alkali upon this anhydride with the taking up of water the
glycylglycine NH2 CH2CO.NHCH2COOH is formed, and according to this prin-
ciple other dipeptides can also be prepared.
Another method which has much greater application consists in the anchoring
of an amino-acid to a halogen of an acid radical, for example, by the action of
brompropionyl bromide or chloride upon glycocoll according to the following
equation
:
CH3CHBrCOCl+NH2CH2COOH=HCl+CH3CHBrCO.NHCH2COOH
1
Journ. of biol. Chem., 9.
2
See Chem. Centralbl., 1911.
3
Biooh. Zeitschr., 17 and 23; see also Abderhalden and C. Funk, Zeitschr. f. physiol.
Chem., 66.
4
Fischer and Gluud, Annal. d. Chem. u. Pharm., 369; Abderhalden and Kautzsch,
Zeitschr. f. physiol. Chem., 72 and 75.
6
Ibid., 64, 65 and 67.
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