Studies in terpenoids. Part 43: Synthesis of (±)-2,6-dimethyl-10-(p-tolyl) undeca-2,6 (E)-diene, the diterpene ofSalvia dorisiana
(±)-2, 6-Dimethyl-10-(p-tolyl) undeca-2,6(E)-diene (1a), a diterpene hydrocarbon from the essential oil ofSalvia dorisiana has been synthesised by two methods. One pot reaction ofp-tolylmagnesium bromide with geranylacetone (5) and hydrogenolysis of the resulting benzylic alcohol (1b) without isolation furnished the natural product (1a). In the other method citrylidene-p-methylacetophenone (6a) was used as the starting material. The trienone (6a) was reduced to the corresponding alcohol (6b) which was hydrogenated to (6c) and oxidised to the dienone (6d). Reaction of the dienone (6d) with methylmagnesium jdoide, followed by dehydration of the carbinol and reduction with lithium in liquid ammonia furnished the diterpene (1a).
KeywordsDiterpene Salvia dorisiana synthesis by one pot reaction geranylacetone citrylidene-p-methylacetophenone
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