4-Hydroxy-3-methylbut-2-enolide

The 13-cw-analogue (56) of (6), was prepared from known [67] phosphonium salt (62) and 4-hydroxy-3-methylbut-3-enolide [77] as indicated in Scheme 1.5. The synthesis of (57), containing a terminal cyclopropyl ring, was effected by Wittig coupling of the ylide from salt (62) with ethyl ( )- 8-formylcyclopropylcarboxylate [78]. 

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