ON ABSORPTION SPECfRA AND CHElWlCIAL CONSTITUTION. 167 



measurements of the photographs of the two series of spectra agreeing 

 almost perfectly. 



The investigation of these compounds was undertaken solely with 

 reference to their suspected homology, but it was at once seen, on examin- 

 ing their spectra, that a close resemblance subsisted between them arid 

 tlie spectra of corydaline and tetrahydropapaverine. The photographs of 

 the spectra of corydaline and laudanosine in particular are almost indis- 

 tinguishable, and suggest a very close structural relation between these 

 two compounds. Laudanosine differs from tetrahydropapaverine by CH.n, 

 and may simply be a homologue of this substance, possibly having a 

 methyl group attached to carbon atom 4. (See papaverine, p. 127.) 



Apart from the closer resemblance of their spectra, however, there is 

 some ground for believing that laudanosine is more nearly related to cory- 

 daline than to tetrahydropapaverine. It differs fi'om corydaline only in 

 having one atom of carbon less in its molecule ; the two substances cannot 

 therefore be homologous, if the formuliB of both have been correctly 

 determined. 



Corydaline has recently been analysed by numerous investigators, with 

 concordant results, and its formula may be regarded as well established. 

 Laudanine and laudanosine, on the other hand, have been but little 

 examined, and there is a possibility that their formulfe may not yet have 

 been definitely settled. Assuming, however, as we are bound to do for 

 the present, that the analyses are correct, cases are known in which sub- 

 stances, other than homologues, which are nearly related structurally, 

 show as close an agreement between their spectra even when their formulae 

 differ more widely than those of corydaline and laudanosine. 



Unfortunately, very little is known of the chemistry of laudanosine, 

 but that little is entirely in favour of the view expressed as to its close 

 relationship with corydaline and tetrahydropapaverine. Like those sub- 

 stances, it contains four methyl groups, and yields metahemipinic acid as 

 one of its products of oxidation. It further resembles corydaline in being 

 optically active and in the ease with which, when heated with dilute nitric 

 acid, it undergoes oxidation to a yellow base. This substance, which has 

 not been analysed, may be identical with meconidine,^ an alkaloid asso- 

 ciated with laudanosine in opium. The formula of meconidine, C.21H23O4N, 

 bears the same relation to that of laudanosine that the formulie of dehydro- 

 corydaline and berberine bear to those of corydaline and tetrahydrober- 

 berine respectively, as the following table shows : — 



Ciiloiirless. Ydlow. 



Corydaline, Dehydi'ocoryd aline, 



Co.,Ho-0,,N, C.oHoaO.N, 



m.p. i35°-5. m.p. 118-120°. 



Tetl-ahydroberberine, Berberine, 



C,„H.„04N, C.oH.^O.N, 



m.p. 167°. m.p. 145°. 



Laudanosine, Meconidine, 



C.,,H.,,0,N, Co.HosO.N, 



m.p. 89°. m.p. 58°. 



* Hesse, Aomalen, 1870, 77, p. 47. 



