Chemical structure and biological activity 



the possibility and tendency that part of the molecule assumes a flat structure 

 )>N=C\ , which mav be considered to take the place of the ring-system 



in the well-known growth substances. By kindly putting a number of these 

 compounds at our disposal Dr. van der Kerk enabled us to test them under 

 our conditions. Fioure 8 and Table 1 show that the compounds XXIII and 



[a) 



ib) 



(c) 



Figure 8. Pea test. 



(a) XXIII : 500, 300, 100, 25, 10, 4.10"=^ /«o///. 



(b) XXIV : 500. 300, 100, 25, 10, 4.10-^ ?«o///. 



(c) XXVI : 500, 300, 100, 25, 10, 4.10'^ moljl. 



XXIV are distinctly active, XXIV being the most active one. When 

 N(CH3)2 is replaced by N(C2H5)2 (XXVI), or C=S by C=0 (XXV), 

 very weak activity or inactivity results, to be expected according to the view 

 expressed by van der Kerk et al., that in these cases the formation of the flat 

 structure with a double bond is favoured less or not at all. 



In the zj-obutyric acid derivative (XXVII) indications for antagonistic 

 activity were found in the suppression of the normal geotropic behaviour of 

 the roots in the cress-root test. 



128 



