Epi-p-santalene

Independently, Koizumi et al. also reported [160] the use of nonracemic 3-p-tolylsulfinylacrylates as dienophiles in highly diastereoselective Diels-Alder reactions. The functionalized bicyclo[2.2.1]heptane derivatives such as (186), obtained by asymmetric Diels-Alder cycloaddition of ethyl p-tolylsulfinylmethylenepropionate with cyclopentadiene, have been used as intermediates for the synthesis of bicyclic sesquiterpenes such as (+)-epi-P-santalene (187) [161,162] (Scheme 5.61). 

The synthesis of (+ )-sesquifenchene (450) and of ( )-epi-P-santalene (451) from the common intermediate (449), derived from endo-dicyclopentadiene, has been detailed. Conversion of (449) into the precursor of (450) makes use of the skeletal rearrangement that occurs during solvolysis of active 2-norbornyl esters. In a synthesis of (-H )-hinesol (452) and 10-epi-(-l-)-hinesol, interesting use has been made of a fragmentation reaction.The tosyl derivative (453), which was obtained in several steps from ( —)-P-pinene, was converted into the spiro[4,5]decane (455) on treatment with sodium hydride in DMSO the essential stereoelectronic changes are summarized in the intermediate (454). 

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