RELATIONSHIP OF MOLECULAR STRUCTURE 

 OF SOME NAPHTHYLOXY COMPOUNDS 

 AND THEIR BIOLOGICAL ACTIVITY AS 



PLANT GROWTH REGULATING SUBSTANCES f 



L. C LucKwiLL and D. Woodcock 

 Long Ashton Research Station, University of Bristol. 



During recent years, despite the considerable amount of work which has been 

 done, particularly with indolyl and phenoxy compounds as growth substances, 

 no systematic investigation of naphthyloxy compounds as growth regulators 

 has yet been reported. One reason for this is doubtless the low activity of this 

 series of compounds in the two tests which have been most widely used for 

 measuring growth substance activity, viz. the Arena curvature test and the 

 coleoptile cylinder test. However, 2-naphthyloxyacetic acid is active in 

 delaying the abscission of petioles (e.g. ofColeus) and in stimulating partheno- 

 carpy in tomatoes, and in our investigations the latter property was utilized 



MEASUREMENT OF BIOLOGICAL ACTIVITY 



This was carried out by observing the rate of growth of unpoUinated tomato 

 ovaries following treatment with known amounts of each compound. The 

 details of the method have been described in a previous publication by 

 Luckwill (1948). Synthesis of these compounds is represented by James 

 and Woodcock (1951, 1953) and Pope and Woodcock (1954, 1955). 



MATERIALS 



The compounds discussed in this paper fall into three main groups, viz. 

 those which have involved an alteration in the side-chain of 2-naphthyloxy- 

 acetic acid, nuclear substituted acids with an altered side-chain, and nuclear 

 substituted 2-naphthyloxyacetic acids. 



CO- (2-NAPHTHYLOXY) -W-ALKYLCARBOXYLIC ACIDS 



Data for ten members of the homologous series of a)-(2-naphthyloxy)-n- 

 alkylcarboxylic acids has appeared in a previous publication by the authors 

 (Luckwill and Woodcock, 1955) and is reproduced in Table 1 by permission 

 of the Editors. 



The outstanding feature of these results is the complete lack of activity of 

 those acids having an odd number of carbon atoms in the side-chain. By 

 contrast )'-(2-naphthyloxy)-n-butyric and f-(2-naphthyloxy)-n-caproic acids 

 with four and six carbon atoms respectively in the chain proved as active in 

 this test as 2-naphthyloxyacetic acid itself, whilst >/-(2-naphthyloxy)- 

 octanoic acid showed definite though reduced activity. Owing to the very 

 low biological activity and low solubility of the two highest members of the 

 series, (-(2-naphthyloxy)-decanoic and A-(2-naphthyloxy)-dodecanoic acids, 



■]■ This paper was read at the Conference by Mr. D. L. Abbott. 



195 



