(-)-Menthol is a major component of the taste and fragrance of peppermint and is widely used in cake — Organic Chemistry Chemistry Question
Menthol synthesis
(-)-Menthol is a major component of the taste and fragrance of peppermint and is widely used in cakes, cosmetics, and tooth powder, etc. (-)-Menthol is anodyne and is used as medicine. (-)-Menthol can be supplied from natural resources such as peppermint oil, but is now synthesized industrially as shown below. It is said that the synthesis supplies about 1/3 of the world demand of (-)-menthol. A key step of the synthesis is 1,3-asymmetric hydrogen migration reaction from amine A to enamine B. A rhodium catalyst with a chiral bidentate ligand developed by Ryoji Noyori (Nobel Prize Winner, 2001, Chemistry) can precisely distinguish enantiotopic hydrogens, HR and HS, and selective migration of Hs provides optically pure enamine B.
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Which molecules include two enantiotopic hydrogens (HA and HB) that are stereochemically similar to two hydrogens (HR and HS) of amine A? Select your answer(s) from all the symbols of the following molecules D – I.
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E, H
Propose a reasonable reaction mechanism of hydrolysis of enamine B to aldehyde C.
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Draw the most stable conformer of (-)-menthol.
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Treatment of (-)-menthol with dilute sulfuric acid causes a dehydration reaction. Predict the major product.
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(-)-Menthol is a monoterpene composed of two isoprene units. Surround the isoprene unit of (-)-menthol in a line.
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