Fragranol synthesis

Cyclobutane.—Grandisol syntheses have been re viewed,and Trost s full paper on grandisol and fragranol synthesis (Vol. 6, pp. 21, 22) has been published. 

This method was successfully applied to the total synthesis of the monoterpene ( )-fragranol 85 [158]. 

The final step involves peracid oxidation and sulfoxide elimination to obtain the desired isopropenyl group. Fortunately, this elimination occurs without isomerization of the double bond and is therefore a useful method for introduction of an isopropenyl unit. Although the synthesis is lengthy, only the compounds formulated are purified, and yields in all steps are >80%. However, the NMR spectrum of the saturated methyl region of the final product indicates that it consists of grandisol and the isomeric fragranol (9) in the ratio 4 1. 

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