64 SECTIONAL ADDRESSES 



In this way there were made a series of derivatives of harmol having the 

 general formula (VIII) given below, the salts of which proved, as had been 

 expected, to be readily soluble in water. 



/\ v\ 



NH CH3 

 (VIII) 



The size of both R (the N-alkyl groups) and x the number of carbon 

 atoms in the chain separating N from O was varied, and the results may be 

 illustrated by reference to a series in which the decyl group (x = 10) was 

 a common factor, whilst the dialkylamino group was varied. 



Minimum concentration lethal 

 Compound. to Entamoeba histolytica. 



0-x-Dimethylaminodecylharmol . i in 300,000 to i in 500,000 



O-x-Diethylaminodecylharmol . . i in 200,000 to i in 500,000 



0-x-Di-n-butylaminodecylharmol . i in 750,000 to i in 2,000,000 

 0-x-Di-«-amylaminodecylharmol . i in 750,000 to i in 3,000,000 



0-X-Di-w-butylaminoundecylharmol . i in 750,000 to i in 4,000,000 



0-«-Nonylharmol . . . . i in 200,000 to i in 500,000 



Emetine hydrochloride . . . i in 2,000,000 to i in 10,000,000 



It was thus found that the activity of members at the peak of the series, 

 such as 0-X-di-w-butylaminoundecylharmol, was many times that of 

 0-n-nonylharmol, and this fact led us to suspect that the harmol residue 

 might not be an important contributor to the amoebicidal properties of the 

 molecule. 



A number of compounds were then prepared in which dibutylaminodecyl 

 (or undecyl) groups were introduced into molecules of varying structures. 

 The last columns in the following tables show the limits of the range of the 

 minimum concentration found lethal to Entafnoeba histolytica in three 

 days, under the conditions laid down by Laidlaw, Dobell and Bishop 

 (loc. cit.). 



Minimum concentration lethal to 

 Compound. Entamoeba histolytica. 



(C,H,),N.(CH,),i.O-[^^J^^^N 



I m 750,000 to I m 4,000,000 



NH CH3 



I m 100,000 



(C,H,),N.(CH,),i.O-l^^^l 



(C4H9)2N.(CH2)ioO.CO.CH3 . . i in 100,000 



(C4H9)2N.(CH2)ioO.CO.C6H5 . . I in 100,000 



(C4H9)2N.(CH2)ioN.(C4H9)2 . . I in 2,000,000 



