Chemistry of Gibberellins From Flowering Plants 479 



Infrared Absorption Spectra 



The infrared absorption spectrum of bean factor I in KBr pellet 

 is identical with that of a sample of Aj supplied by Stodola. 



The infrared absorption spectrum of bean factor II in KBr pellet 

 resembles in a general way those of the fungal gibberellins, but there 

 are some distinct differences. Some absorption maxima for bean fac- 

 tor II and tentative structural assignments based on similar features 

 of fungal gibberellins are as follows: 



3400 cm-i alcoholic hydroxyl 



1750 cm-i y-lactone carbonyl 



1720 cm-i carboxylic acid carbonyl 



1650, 890 cm-i )C=CHo 



1620 cm^ ethylenic double bond 



DISCUSSION 



The identity of the infrared spectra of bean factor I and an au- 

 thentic sample of Aj leads to the conclusion that bean factor I and 

 Ai are the same compound. All the other properties determined are 

 consistent with this conclusion. Thus, there are three species of flow- 

 ering plants which have been shown to contain Ai as a natural con- 

 stituent in small amounts — immature seed of Phaseolus midtifloriis, 

 immature seed of Phaseolus vulgaris, and water sprouts of Citrus 

 unshiu. 



The properties of bean factor II indicate that it is structurally 

 similar to the fungal gibberellins but not identical with any of those 

 reported to date. The presence of a carboxylic acid group is clearly 

 indicated, and the neutral equivalent is in the range of those of the 

 fungal gibberellins. A y-lactone group is also indicated by the infra- 

 red spectrum. The evidence also suggests the presence of one alco- 

 holic hydroxyl group. Two ethylenic double bonds are present per 

 acid equivalent. One of these is most likely bonded to a terminal 

 methylene group. These two double bonds are not in conjugation 

 with other sites of unsaturation since bean factor II does not show 

 an ultraviolet absorption maximum above 220 m/x. If the seemingly 

 reasonable assumption is made (for which there is no direct evidence) 

 that bean factor II has the same carbon skeleton as the fungal gibber- 

 ellins and the exocyclic methylene group is as in A^, A3, and A4, then 

 the following positions seem the most likely possibilities for the sites 

 of unsaturation. 



