Short synthesis of the C16-C28 polyketide fragment of apoptolidin A aglycone.

Starting from (E,E)-1-[(1R)-(phenylethyl)oxy]-2-methylpenta-1,3-diene and triethylsilyl enol ether of butanone rapid access to Koert's advanced C10-C28 polyketide fragment of apoptolidin A is now possible.

Sulfur dioxide-mediated syntheses of polyfunctional alkenes and (E,Z)- and (E,E)-2,4-dien-1-ones.

Efficient methods for the stereoselective synthesis of polyfunctional (E)- and (Z)-alkenes and conjugated (E,E)- and (E,Z)-dienones are presented. They rely upon one-pot, four-component processes that condense 1-oxy-1,3-dienes, silyl enol ethers, SO2, and carbon electrophiles. [structure: see text]

Silyl methallylsulfinates: efficient and powerful agents for the chemoselective silylation of alcohols, polyols, phenols and carboxylic acids.

Alcohols, phenols and carboxylic acids are silylated with very good yields in the presence of silyl methallylsulfinates under non-basic conditions and with the formation of volatile co-products.

Palladium-catalyzed conversion of beta,gamma-unsaturated silyl sulfinates into (E)-alkenes: asymmetric synthesis of polypropionate fragments.

At low temperature, 1-alkoxy-1,3-dienes add to sulfur dioxide activated by a Lewis or protic acid generating zwitterionic intermediates that can be quenched by enoxysilanes. The resulting beta,gamma-unsaturated silyl sulfinates can be desilylated by 1:1 Pd(OAc)(2)/PPh(3) catalyst, liberating the corresponding beta,gamma-unsaturated sulfinic acids that undergo smooth and highly stereoselective retro-ene eliminations of sulfur dioxide. The method has been applied to generate enantiomerically pure polypropionate fragments.