132 BACTERIOLOGICAL CHEMISTRY 



SO2NH2, is regarded as being at position 1, whilst the 

 amino group is at position 4 : — 



SO,NH,. 



/ ' \ 



\ 4 / 

 NH2 

 The following is a summary of the findings : — 

 N^ derivatives. 



(a) Alkyl. The introduction of the methyl or ethyl 

 group causes little change in effectiveness. 

 Longer chains cause lowered activity. 

 (h) Isocyclic. About 180 have been prepared, none 



of which have been of much value. 

 (c) Heterocyclic. About 250 have been synthesised. 

 They include the most useful members loiown. 

 Among them are sulphapyridine, 



CH 



CH CH 



-\, I " 



NH/ >S02.NH— C CH 



N 



effective against pneumococcal, streptococcal, 

 meningococcal, gonococcal and coli infections, 

 sulphathiazole, N— CH 



NH,^ ^SO,.NH— C CH. 



s 

 effective against staphylococci, and sulphadia- 



CH 



/% 



zme, II I , which is 



NH,/ \S0,.NH— C CH 



^ — 



