Polyketides ether formation

P. Poplau, S. Frank, B.l. Morinaka, J. Piel, An Enzymatic domain for the formation of cyclic ethers in complex polyketides. Angew. Chem. Int. Ed. 50,13215-13218 (2013)... 

Kishi has conducted a comprehensive series of investigations on acyclic stereocontrol in OsO,-catalyzed dihydroxylation of allylic alcohols and ethers [191, 195). These studies were prompted by the synthetic problems presented by one of the most complex polyketides synthesized to date palytoxin [196], The observed stereoselectivity trends in dihydroxylations of allylic substrates such as 265 and 268 led Kishi to propose the empirical model 271 for predicting the diastereoselectivity (Scheme 9.34) [191, 195]. In this model, minimization both of A 1,3 strain and of electrostatic repulsions between 0s=0 and the ether oxygen (cf. 266 and 269) are believed to lead to predominant formation of the 1,2-anti products 267 and 270, respectively. 

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