Total syntheses of spirovetivanes and khusimone

The essential oil of vetiver, Vetiveria zizanioides (L.) is one of the most important raw materials in modern perfumery. The grass is cultivated in many tropical and subtropical regions and the commercial oil is isolated by steam distillation of the roots. Traditionally Java, the Reunion Islands, and the Seychelles were the major producers but more recently a substantial portion of the total output comes from Haiti, Japan, Brazil, and India, Because of its commercial importance chemical analysis of this essential oil has been given much attention and over fifty compounds have thus far been isolated and identified.

The majority of these substances belong to the sesquiterpene group of natural products. Among these α-vetivone, β-vetivone, the norsesquiterpene khusimone, and three biogenetically derived C12-ketones provided the most exciting chemistry. Since the spiroketone and khusimone appear to play a significant role in the reconstitution of the essential oil, we have developed total syntheses of these substances. In an earlier synthesis of the spiroketone, β-vetivone was utilized as starting material; and more recently it has also been prepared by a photochemical route. Among the many published syntheses of β-vetivone two deserve special mention because of their elegance and stereo selectivity.

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