What is Tropinone?

Tropinone is a tropane alkaloid, usually in needle-like crystals (gasoline), used as an intermediate in the synthesis of atropine sulfate. It is an alkaloid molecule worth mentioning in the history of organic synthesis.

Use tropinone to react with dimethyl carbonate in the presence of alkali to generate 2-methoxycarbonyl tropinone, and then hydrogenate the product in the presence of Raney nickel to generate methylecgonine, and finally methylecgonine is combined with Cocaine can be obtained by esterification of benzoyl chloride in the presence of pyridine.

The synthetic method of Tropinone

Wierstedt (1915 Nobel Laureate in Chemistry) used cycloheptanone as the starting material. Although the yield of each step in the route was high, the total yield was greatly reduced due to the number of steps, only 0.75%. . Of course, it was a great contribution to the development of synthetic organic chemistry to be able to synthesize such complex compounds artificially in the early 20th century. This was one of the important events in the early assembly of complex natural products in the laboratory. The successful assembly of this rather complex natural molecule was the culmination of organic synthesis in the classical period, marking the birth of multi-step total synthesis.

Before the synthesis of tropinone​, Willstätter had successfully synthesized cocaine for the first time with tropinone as a raw material in 1898, and elucidated the structure of cocaine.

In 1917, Robert Robinson created a brief synthesis of tropinone. This method is one of the classic routes in organic synthesis. It only uses succinaldehyde, methylamine and 3-oxoglutaric acid with simple structure as raw materials. Under biomimetic conditions, the Mannich reaction is used, and only three steps are carried out. (one-pot reaction) tropinone was synthesized, and the yield reached 17%, which could exceed 90% after improvement.