THE CHEMISTRY OF THE PROTEINS 93 
was thus proved to be a-amino-8-oxypropionic acid, the isomeric 
compound, isoserine, being 8-amino-a-oxypropionic acid. 
Leuchs and Geiger have since found a better method for the 
synthesis of serine, from chloracetal, which is best described by 
the following formule : 
dil 
OCH, NaOC,H, OC.H; H,SO, 
Cl: CH;. CH ->  C,H;,O.CH,.CH “5 
OC.H, : OC.H, 
HCN+ 
NH, 
CAH; -O. CH CHO. => 
HO conc.HBr. 
eH; . 0. CH, .CH(NH,). CN => C,H;OCH,.CH(NH,). COOH > 
HO.CH,.CH(NH,). COOH 
By the same method Fischer and Leuchs have prepared a-amino- 
y-oxyvalerianic acid, a compound which behaves like the other 
y-oxy acids in easily forming an anhydride or y-lactone giving 
the base 
CH,. eh — CH,. CH(NH,). CO 
O 
This substance readily polymerises to a diketopiperazine, a 
condensation made much use of in the synthesis of proteins. 
Like the oxyaldehydes, the carbohydrates combine with 
hydrogen cyanide and ammonia; thus, d-arabinose gives 
d-glucosaminic acid, which is identical with the product obtained 
by the oxidation of glucosamine. Fischer and Leuchs were by 
this means able to determine the constitution of this important 
compound. 
The oxyamino acids, according to Fischer, are of extreme 
importance on account of their relationship on the one hand to 
the carbohydrates and on the other hand to the proteins, in 
which they probably occur to a much larger extent than is at 
present known. 
Another ‘oxyamino acid, 6-oxy-a-aminovalerianic acid, has 
been synthesised by Sérensen, by a method similar to that 
employed by Fischer in the synthesis of the diamino acids. It 
is isomeric with Fischer’s a-amino~y-oxyvalerianic acid, and 
constitutes another member of the series of the oxyamino acids. 
Compared with the monoamino acids the diamino acids are 
much more difficult to obtain synthetically. The only diamino 
