ox ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION. 127 



narcotine, and narceine — has now been definitely determined, and the 

 examination of this group furnishes a good basis for the study of the 

 relationship between the absorption spectra and the constitution of the 

 alkaloids. 



Since papaverine is, in some respects, more simply constituted than the 

 other members of the group, it will be convenient to consider each of the 

 others with reference to it. According to Goldschmiedt, the structure of 

 papaverine is represented by the following formula : 



Papaverine. 



f^NoMe 

 I MOMe 



i 

 MeO ''■ ' '" • 



The absorption curve of papa\erine shows two absorption bands, the 

 first lying between ^/X 2998 (\=3335) and V\ 3295 (A=3035), and the 

 second between \/\ 3956 (\=2528) and ^X 4555 (\ = 2195). 



Hydrastine differs structurally from papaverine in the following par- 

 ticulars : (i) The isoquinoline nucleus is partially reduced ; (ii) The two 

 methoxyl radicals of the z'soquinoline nucleus are replaced by a dioxy- 

 methylene group ; (iii) A methyl group is attached to the nitrogen atom ; 

 (iv) A carbonyl group is attached to the carbon atom (4), and through 

 the medium of an oxygen atom is also linked to carbon atom (2), which 

 has only one atom of hydrogen attached to it. From this comparison, it is 

 obvious that the two substances differ considerably in their constitution. 

 On comparing the curve of the absorption spectra of hydrastine (fig. 4) with 

 that of papaverine (fig. 2), it will be seen that there is a correspond- 

 ingly wide difference between them ; hydrastine exhibits slightly less 

 general absorption than papaverine, and shows only one absorption band 

 which is wider and much more persistent than either of the absorption 

 bands of papaverine. Narcotine only differs from hydrastine in con- 

 taining an additional methoxyl group attached to ring IV, and the 

 two alkaloids give practically identical absorption spectra (figs. 4 

 and 5). Assuming the constitution of corydaline, as determined by 

 Dobbie and Lauder, to be correct, it is represented by the second of 

 the following formulse : 



^rt 



Tetrahydroberberine, Corydaline. 



,^\0Me ^^OMe 



„ I ' lOMe jr /L >OMe 



Hj Ho 



