474 



C. A. West 



Sumiki and his collaborators at the University of Tokyo interpret 

 their results to indicate the same structure for Ai and A3 as above, 

 except for the {position of the lactone ring in ring A (4, 8, 10). They 

 report that lithium aluminum hydride reduction of the methyl ester 

 of Aj leads to a product which could not be oxidized by periodate. 

 They also reported the isolation of a degradation product from the 

 lithium aluminum hydride reduction product which was identified 

 as a l,3-dimethyl(luorene derivative. In line with their findings they 

 propose the A rings of A^ and A3 to have the following structures: 



Sumiki and his co-workers have also proposed structures for gib- 

 berellin Ao (A2) and gibberellin A4 (A4) which they have isolated from 

 the fungal filtrates. Both are thought to have the same A-B ring struc- 

 tures as Aj but are modified in the C-D rings as follows: 



A4 



There is now abundant evidence for the presence of substances 

 with biological properties similar to those of the fungal gibberellins 

 in flowering plant tissues. The obvious implication is that such sub- 

 stances act as natural regulators of growth and development in the 

 plant. It is important, therefore, to isolate these substances and de- 

 termine their structure if we are to approach intelligently questions 

 regarding their role in controlling growth and development, the mode 

 of their biosynthesis, and the mechanism of genetic control of these 

 processes. 



