CHEMISTRY: T. B. JOHNSON 
71 
On the other hand, when heated with acids, they easily undergo inner 
condensation with transformation into their corresponding anhydrides 
or hydantoins I. The latter compounds are very resistant to further 
hydrolysis with acids as has been shown by investigations in this 
laboratory. 
NH-CO NH2 COOH 
CO 
CO 
-> NH3 + CO2 + NH2CH2COOH. 
NH - CH2 NH - CH2 
(I) (11) 
While this explanation of Lippich's is in concordance with the chemical 
nature of hydantoic acids, on the other hand these compounds (II) 
do not represent the only types of uramido combinations which can 
undergo hydrolysis with formation of carbon dioxide and a-amino acids. 
One point needs to be taken into consideration here and that is the fact, 
that for every molecule of carbon dioxide formed by hydrolysis of a 
hydantoic acid II an equivalent amount of ammonia must also be ob- 
tained. Apparently this ratio C02:NH3 has never been estabHshed 
quantitatively in the case of a single protein 
Theoretically it is possible to link together two a-amino acids in a 
cycHc urea combination in such a manner that the resulting compound 
will undergo hydrolysis with production only of carbon dioxide and 
a-amino acids. If we choose glycocoll III and alanine IV as the two 
amino acids and combine them in the form of hydantoins as represented 
by formulas VII and VIII, two isomeric cyclic combinations will be 
obtained which will fulfil the above conditions. In other words, they 
are cycHc derivatives of the two isomeric dipep tides — glycylalanine V 
and alanylglycine VI respectively, in which the characteristic poly- 
peptide groupings of the dipeptides have been preserved. Such com- 
binations are the representatives of a new class of hydantoins, 
NH2CH2COOH NH2CH(CH3)COOH 
i (III) i (IV) 
NH2CH2CONHCH (CH3) COOH NH2CH (CH3) CONHCH2COOH 
i (V) i (VI) 
NH • CH2CO • NCH (CH3) COOH NH - CH (CH3) CONCH2COOH 
' — CO J (VII) I CO 1 (VIII) 
hydrolysis 
CO2 + NH2 • CH2COOH -f- NH2CH (CH3) COOH, 
