Ether transfer, polyketide synthesis

ETHER TRANSFER METHODOLOGY APPLICATION TO THE SYNTHESIS OF POLYKETIDE NATURAL PRODUCTS... 

Challenged by this synthetic problem, our laboratory sought to develop an ether transfer protocol that stereose-lectively generates ether functionality and provides additional synthetic handles enabling the development of strategically novel approaches to the synthesis of structural units common to polyketide natural products." As an extension of Bartlett et al. s carbonate process initiated with IBr, the methoxymethyl-protected homallylic alcohol... 

SCHEME 37.19. Ether transfer methodology in the synthesis i>>n-l,3-diol /tw-methyl ethers in a single step a rapid access to large polyketide structural units. 

Ley et al. previously demonstrated the synthetic value of 2-sulfonylpyrans for the synthesis of 2,6-cis and 2,6-tra 5-tetrahydropyran. These more complex systems resulting from the ether transfer contain oxidation and the 4-position common to many polyketides. Conversion of intermediate sulfone 96 into 4-methoxy-2,6-tra/Js-tetrahydropyran 97 was accomplished by direct ionization of the sulfone in the presence of aluminum trichloride and a nucleophile (Scheme 37.24). ... 

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