Ethers allyl silyl, ozonolysis

The ozonolysis of substituted-allyl silyl ethers or allyl esters followed by treatment with bases or Ph3P give the corresponding a-silyloxy ketones or a-acyloxy ketones.116 The reaction is proposed to proceed via an ene-diol rearrangement of the corresponding a-silyloxyaldehyde or a-acyloxyaldehydes intermediates. 

The synthetic utility of (i )-enoate 392 is illustrated in the stereoselective synthesis of the bengamide E derivative 399 (Scheme 88). Silyl protection of 392, reduction with DIBAL, and Sharpless epoxidation of the resulting allylic alcohol furnishes epoxy alcohol 396 as a 95 5 anti syn mixture. Conversion of the primary hydroxyl group of 396 to an iodide under neutral conditions followed by a metallation-elimination and subsequent in situ methylation provides the ether 397. Ozonolysis, desilylation with aqueous acetic acid, and a Dess-Martin oxidation supplies the a,jS-dialkoxy aldehyde 398. This, utilizing stannane Se addition, is then converted to 399 [135]. 

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