Eldana saccharina synthesis

Butenolide 1012 is a key intermediate in the synthesis of ( + )-eldanolide (1013), a pheromone of the African sugar-cane borer Eldana saccharina. It is synthesized in 5 steps and 48% overall yield from (7 )-malic acid v/a (7 )-l,2,4-butanetriol (984) (Scheme 150) [218]. 

The Ueno-Stork reaction is a radical cyclization of the a-haloacetal of an aUylic alcohol that provides substituted tetrahydrofuran and y-lactone derivatives. The chiral center of the aUylic moiety can control the stereochemical outcome, and the stereoselectivity may also be affected by the conformational anomeric effect. The Ueno-Stork radical cyclization has been applied in the synthesis of (-l-)-eldanolide (Scheme 25.22)," the pheromone of the male African sugarcane stem borer Eldana saccharina, in which bromoacetal 49 evolves to 50. The stereochemical outcome of these reactions is rationalized by a chair-like transition state, in which the adopted conformation maximizes the anomeric effect of the acetal center. 

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