fHE CHEMISTRY OF .-LHE -PROTEINS 95 
y-cyanopropylmalonic ester, on treatment with nitrous acid, 
loses one of its carboxyethyl groups and forms the ethyl ester 
of a-oximido-é-cyanovalerianic acid. On reduction with sodium 
amalgam this compound yields a-e-diaminocaproic acid, thus: 
NC. CH;. CH:. CH:. CH Ep act? -> NC. CH, .CH,C(: N.OH). COOC,Hs-> 
H,N.CH,.CH;. CH,. CH(NH;). COOH 
This acid has also been synthesised by Sérensen by a very 
similar method, but its separation into its stereoisomers has not 
yet been carried out and identity of one of its isomers with 
natural lysine confirmed. 
Fischer and Schlotterbeck have prepared another diamino- 
caproic acid by heating sorbic acid with ammonia, but its 
structure has not yet been determined ; another diaminovalerianic 
acid has been obtained from 8-vinylacrylic acid. 
The other hexone base, histidine, has not been synthesised 
by Fischer. Its constitution, as suggested by Pauly and proved 
by Windaus and Knoop, though not yet quite definitely 
determined, is that of imidazoleaminopropionic acid : 
NH = CH 
\n 
CH {ec 6H. CH. NH, Coon 
Most probably the amino group is in the a-position, but this 
still awaits the final proof. 
Of the heterocyclic products, proline, as above mentioned, 
was prepared synthetically by Willstatter. 
' Two oxypyrrolidine carboxylic acids have recently been 
obtained by Leuchs in Fischer’s laboratory, and deserve mention 
here in order to complete our knowledge of the amino acids. 
They were obtained as follows: 
y-chlor-8-oxypropylmalonic ester, prepared from epichlor- 
hydrin and sodium malonic ester, loses alcohol and passes into 
the ester of 6-chlor-y-valerolactone-a-carboxylic acid : 
O CO 
| | 
CH,. Cl. CH.CH,. CH .COOC,H; 
This compound on bromination, hydrolysis with concen- 
trated hydrobromic acid and subsequent splitting off of carbonic 
acid, gives a-brom-6-chlor-y-valerolactone, which on treatment 
