Natural Sources and First Technological Production of -Menthol

2 Natural Sources and First Technological Production of (—)-Menthol 

Reagents and conditions /. propyiene-Si02/Ai203 //. H2-CU chromate catai.  

All the knowledge accumulated over the years at Takasago Research Institute, Tokyo, headed by S. Akutagawa, and by the research team of R. Noyori, Nobel Laureate for chemistry in 2001, prompted the development of an industrial process for the production of (—)-menthol by this method. Superficial observation of this scheme, and the list of reagents cited for the steps i-v, do not reveal the impressive mechanistic knowledge which has been gained on nearly all steps on this route to (—)-menthol. Already in the first step (/), reaction conditions in the alkylation of 

The final mechanistic pathway (c), the so-called nitrogen-triggered mechanism, is responsible for the enantioselective route to (—)-menthol. It comprises, first, co-ordination to the electronegative N-heteroatom followed by abstraction of the acidic a-proton and formation of the three-membered metaUacycle. This intermediate 

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