CHEMISTRY: JOHNSON AND TICKNOR 
303 
A NEW METHOD OF TRANSFORMING ESTERS OF a-AMINOACIDS 
INTO THEIR CORRESPONDING ISOTHIOCYANATES 
By Treat B. Johnson and Arthur A. Ticknor 
SHEFFIELD SCIENTIFIC SCHOOL. YALE UNIVERSITY 
Communicated by L. B. Mendel. February 28, 1917 
In a previous paper from this laboratory/ the writer called attention 
to the chemistry of polyketide mustard oils of the type C2H5OOC.CHR. 
NCS, and indicated the need of a practical method for preparing such 
combinations in quantity for synthetical work. This problem was un- 
dertaken by us and a method of synthesis was developed whereby iso- 
thiocyanates of the above type can be prepared directly from esters of 
a-aminoacids by subjecting the latter to the action of thiophosgene in 
dry toluene solution. For example, ethyl aminoacetate, in the from of 
its hydrochloric acid salt, interacts smoothly with thiophosgene in boil- 
ing toluene giving an excellent yield of the corresponding mustard oil — ■ 
ethyl isothiocyanacetate. The transformation is expressed by the fol- 
lowing equation: This reaction 
CSCI2 + HCI.NH2CH2COOC2H5 = 3HC1 -^ SCN.CH2COOC2H5, 
has now been applied successfully in other cases and the results obtained 
will be published later in the Journal of the American Chemical Society. 
While the above method of synthesis offers no difficulty so far as ma- 
nipulation is concerned, it does involve in its application, however, the 
used of thiophosgene, which is an unpleasant reagent to work with and 
requires much time to prepare in quantity. We have now developed a 
method of operation whereby we are able to convert esters of a-amino- 
acids into their corresponding isothiocyanates without the use of this 
disagreeable reagent. In this preliminary note we record the principle 
of this method and its application for the preparation of ethyl isothio- 
cyanacetate. 
Emil Fischer^ has shown that the ethylester of glycocoll interacts 
quantitatively with carbon-bisulphide in ether solution to form the 
dithiocarbamic acid salt represented by Formula I. The reaction is 
expressed by the following equation : 
CS2 + 2NH2CH2COOC2H6 = NH.CH2COOC2H5 
I 
CSSH.NH2CH2COOC2H5. (I) 
As far as we are aware, this is the only ester of an a-aminoacid that has 
