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Synthesis and odor characteristics of some 6,6-dimethylbicyclo [3.1.0] hexane derivatives

Contact Author Miroslaw Walkowicz and Stanislaw Lochynski, Jozef Gora
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Monoterpenic compounds containing the bicyclo[3.1.0]hexane system, for example, sabinene, sabinene hydrate, thujone, thujyl alcohol, or umbellulone, are the substantial sensorial components of many essential oils of plants from the Cupressaceae, Compositae and Labiatae family. Synthetic analogs of these compounds, and especially their odor qualities, are relatively little known. During several years of studies on the chemical transformations and stereochemistry of the carane system, some simple preparative methods of synthesis of bicyclo[3.1.0]hexane derivatives from 3-carene were elaborated. Utilizing these methods and the standard means of extension of the side chains, a series of new compounds, containing the bicyclo [3.1.0]hexane system with various substituents at the 2- and 3-position, was synthesized.

The starting material for all syntheses was (+)-3-carene (1), which gave, through intermediate 3,4-dibromocarene, trans-3-acetyl-6,6-dimethylbicycIo[3.1.0]hexane (2), the substrate for syntheses of further derivatives substituted at C-3. Ketone (2) was converted into acetate (3) by the Baever-Villiger oxidation, and (3) into alcohol (4). This alcohol gave 6,6-dimethylbicyclo[3.1.0]hexane-3-one (5) by oxidation. The degradation of ketone (2) to acid (6) and its reduction with lithium aluminum hydride (LAH) gave alcohol(7).

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