Isodaucane sesquiterpene

The isodaucane sesquiterpene (+)-aphanamol I was synthesized in the laboratory of B. Wickberg using the DeMayo cycloaddition as the key step. The required starting material 3(S)-isopropyl-1-methylcyclopentene was prepared by the Tsuji-Wilkinson decarbonylation of the corresponding a,p-unsaturated aldehyde. 

Hansson, T., Wickberg, B. A short enantiospecific route to isodaucane sesquiterpenes from limonene. On the absolute configuration of (+)-aphanamol I and II. J. Org. Chem. 1992, 57, 5370-5376. 

The Harmata laboratory has made really important contributions to the study of the (4 + 3) cycloaddition, and an early example of an application is the synthesis of aphanamol, an isodaucane sesquiterpene. From a very simple starting material, the precursor was readily prepared and subjected to triflation and the in situ cycloaddition, thus furnishing aphanamol (Scheme 29) [66]. 

Mehta, G., Krishnamurthy, N., and Karra, S.R. (1991) Terpenoids to terpenoids Enantioselective construction of 5, 6-, 5,7-, and 5,8-fused bicychc systems. Apphcation to the total synthesis of isodaucane sesquiterpenes and dolastane diterpenes. J. Am. Chem. Soc., 113, 5765-5775. 

Bonds from C-1 to C-7 and from C-1 to C-10 in famesane formally build up the sesquiterpene skeleton of isodaucanes which are converted to daucanes by migration of one methyl group (C-14) from C-7 to C-8. 

Aphanamol 1181 is a member of the isodaucane family of sesquiterpenes, which contains a bicyclo[5.3.0]decane ring (Figure 19.19). Interest in this compound is derived from the meliaceous iplsaAAphanamixis grandifolia from which it was isolated [89]. One of the first natural products prepared utilizing an intramolecular [4+3] cycloaddition was aphanamol I as executed by Hannata and Carter [90]. 

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