An approach to the synthesis of phomactins using a Wittig rearrangement

Preliminary studies to evaluate the feasability of an approach to the synthesis of the phomactin diterpenes are outlined. The key step is the 2,3-Wittig rearrangement of the propargylic ether 32 which gives a mixture of the diastereoisomeric alcohols 33. Oxidation to the ketones 34 and 35 followed by conjugate addition of lithium dimethylcuprate and deprotection gives the unsaturated diketone 37 so providing a strategy for the synthesis of the cyclohexenyl core of the phomactins.