ALKALOIDS 369 



changes within the plant are the methylation of hydroxyl or 

 amino groups by formaldehyde, according to the equations — 



ROH + CH2O = ROCH3 + o 

 and RNH + CH^O = RNCHj + O 



the resulting methylated compounds being then able to 

 undergo intramolecular transformation, by which the methyl 

 group can enter the ring, and so produce, for example, a 

 pyridine ring from methyl pyrrole, a reaction which he has 

 been able to effect in the laboratory by heat — 



CH 

 CH CH CH CH / \ 



II II -^11 II -^ ^^ ^^ 



CH CH CH CH II I 



\ / \ / CH CH 



NH NCH3 \ ^ 



N 



Pyrrole Pyridine 



Similar changes would also explain the formation of 

 quinoline and isoquinoline, and it thus becomes possible to 

 account for the origin of the pyridine and quinoline rings 

 which occur in alkaloids, by assuming them to have been 

 produced as above from pyrrole or indole rings, which are 

 the normal constituents of protein (e.g. proline, histidine, 

 tryptophane, etc.). 



In support of these views, Pictet states that he was able 



to isolate by steam distillation from various leaves,* etc., 



treated with sodium carbonate, a number of simple bases which 



he calls proto-alkaloids ; these include pyrroHdine and methyl 



pyrroline — 



CH, CH, CH^=CH 



. I " I i I 



CH2 CHj CH., CH2 



\ / \" / 



NH NCH3 



Pyrrolidine Methyl pyrroline 



whose origin from the protein molecule is readily intelligible, 

 in view of the fact that a similar ring occurs in proline, the 

 cleavage product of a number of proteins. It is assumed that 

 these proto-alkaloids are subsequently methylated, rearranged 



* The leaves used were those of tobacco, carrot, parsley and coco. 



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