Synthesis method of cedrene cis-diol

The present patent application concerns a synthesis method of cedrene cis-diol of formula I comprising the following steps: a) providing α-cedrene of formula II and carrying out the regioselective and stereospecific reaction of α-cedrene of formula II 5 to give cedrene epoxide of formula III, b) carrying out the stereospecific isomerization reaction of cedrene epoxide of formula III to give cedranone of formula IV, c) carrying out the regioselective and stereospecific hydroxylation reaction of cedranone of formula IV to give hydroxycedranone of formula V, d) carrying out the stereoselective reduction reaction of hydroxy cedranone of formula V to give cedrene cis-diol of 10 formula I, characterized in that: in stage a) of the stereospecific epoxidation reaction, the reaction is carried out using a lipase enzyme and hydrogen peroxide, and the reaction temperature is comprised between 20 °C and 35 °C, and the cedrene epoxide of formula III is used as is, i.e. without the need for purification, in the next stereospecific isomerization step b); in 15 stage b) of stereospecific isomerization reaction, the reaction is carried out using a Brönsted acid, and the reaction temperature is comprised between 20 °C and 85 °C, and cedranone of formula IV is purified by distillation; in stage c) of regioselective and stereospecific hydroxylation reaction, the reaction is carried out in the presence of a strong base, and the reaction temperature is comprised between 20 °C and 30 °C, and 20 the hydroxycedranone of formula V is purified by crystallization; in stage d) of stereoselective reduction reaction, the reaction involves the following two sub-steps: d1) adding a Lewis acid, followed by d2) adding a reducing agent, and the reaction temperature is comprised between -5 and 0 °C, and the cedrene cis-diol of formula I is purified by crystallization; in each of the aforementioned steps a)-d) the compounds 25 of formula III, IV, V and I are obtained respectively in a diastereomeric mixture with a diastereoisomeric ratio > 99:1.