Coumarins preethulia

In a similar manner, reaction of enol ether 2-787, hydroxycoumarin (2-781), and a-diketone 2-786 led to the cycloadduct 2-788 in 79% yield using Yb(OTf)3 as catalyst (Scheme 2.174). 2-788 could be transformed into the natural product preethulia coumarin (2-789). 

Preethulia coumarin 253 (Scheme 12.36) represents a naturally occurring analogue of ethuliacoumarin, a prenylated polyketide. 

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