CHAPTER 3 



yV-ETHYLMALEIMIDE 



The early work on maleate as an SH reagent by Morgan and Friedmann 

 in Hopkins' laboratory in Cambridge around 1938 was continued by Fried- 

 mann and his associates, using the imides of various unsaturated dicar- 

 boxylic acids. They established that these imides react much more rapidly 

 than maleate with thiols and are potent antimitotic agents (Friedmann 

 et al., 1949; Marrian, 1949). During the past few years one of the substituted 

 imides, namely A^-ethylmaleimide, has been used as a selective SH reagent 

 in various fields of research, and it appears that this substance will retain 

 for some time its important place in enzymic and metabolic studies. It 

 is a relatively recent inhibitor and 90% of the reports on its actions have 

 appeared since 1957, 60% in the 4 years between 1960 and 1963. Since 

 1960 there have been about 30 publications each year on A^-ethylmaleimide, 

 and this number is at present steadily increasing. 



CHEMICAL PROPERTIES 



iV-Ethylmaleimide is one of a number of iV-substituted maleimides which 

 react readily with thiols. Others members of this group have not been 

 thoroughly investigated or compared with A^-ethylmaleimide, and quite 

 possibly more useful SH reagents of this type are yet to be found. Since 



HC— C 



II > 

 HC— C 



^\> 



Maleimide 



iV-ethylmaleimide reacts with SH groups because of its C=C bond, it 

 would be valuable occasionally to compare its effects with those of succin- 

 imide or A^'-ethylsuccinimide, these possessing the general structural features 

 of maleimide and iY-ethylmaleimide without having the ability to react 



337 



