In pyridine one of the CH groups of the benzene ring is replaced by a nitrogen atom, the formula of the substance being C5H5N. In 1886 Ladenburg succeeded in synthesising the alkaloid coniine, starting with pyridine. This was the first occasion on which the artificial preparation of an alkaloid was achieved. The steps of the process were as follows;—
By the action of methyl iodide (CH3I), pyridinium methyl iodide is formed, which is transformed on heating into [Greek: a]-methyl-pyridine hydriodide. The free base, when treated with acetaldehyde (p. 271), yielded a compound known as [Greek: a]-allyl-pyridine, which, in turn, was made to combine with nascent hydrogen. The resulting compound (isoconiine) becomes coniine on heating to 300° C. or boiling with solid potash. The chemical history is shown graphically below:—
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Pyridine. [Greek: a
-Methyl-pyridine. [Greek: a]-Allyl-pyridine. Coniine.
]
Pyridine, it may be mentioned, can be built up from its elements.
This coniine triumph of synthetic chemistry has been followed by many others of a similar character, and now all the alkaloids mentioned above in connection with pyridine have been produced artificially. Piperine was synthesised by Ladenburg and Scholtz in 1894; atropine together with other solanaceous alkaloids, and cocaine[1] by Willstätter in 1901-2; and nicotine by Pictet in 1903. The structure of these alkaloids is considerably
- ↑ Synthetic cocaine and other artificial alkaloids differ from the natural products only in being without action on polarised light.
