Seven-Ring Annulation: A Linch-Pin Approach to a Tetracyclic Precursor of the Lathrane Diterpenes

Article abstract of DOI:10.1021/jo00251a001

The synthesis of a chiral tetracyclic intermediate (5b) as a precursor of the lathrane diterpenes is described.The key step is the addition of chiral thioacetal 47 to a chiral vinyl sulfone 40 in the abscence of HMPA.Further elaboration of the resulting intermediate 59 provided enol ether 67, which was cyclized with dimethyl(methylthio)sulfonium tetrafluoroborate to give the tetracyclic intermediate 5b.