Jegers Ketal from Manool

4 Jeger s Ketal from Manool. Manool (8.42) is another labdane terpenoid which has found use as a precursor for fragrance ingredients with an ambergris odour. It differs from sclareol in that it has an 

Otto Jeger who first synthesised it. It has a powerful ambergris odour and is highly prized in perfumery. 

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Jeger s ketal (394), named after its discoverer, but also called Amberketal, Ambrake-tal, and Ketamber, is another material with a powerful ambergris odor. It is prepared from manool (395), extracted from the New Zealand tree Dacrydium biforme, by permanganate oxidation to the ketone (396) followed by osmylation of the double bond and spontaneous formation of the ketal from the resultant diol-ketone. It has also been synthesized from larixol (397), which is readily available from the European larch, Larix decidua 449). 

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