Home » Asymmetric Michael additions of lithium propionate enolates to alpha,beta-unsaturated esters: A study towards the total synthesis of lonomycin A. by Sunjin Jo
Asymmetric Michael additions of lithium propionate enolates to alpha,beta-unsaturated esters: A study towards the total synthesis of lonomycin A. Sunjin Jo

Asymmetric Michael additions of lithium propionate enolates to alpha,beta-unsaturated esters: A study towards the total synthesis of lonomycin A.

Sunjin Jo

Published
ISBN : 9780549719830
NOOKstudy eTextbook
421 pages
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The Michael addition of lithium enolates to alpha,beta-unsaturated esters is considered to be one of the powerful and widely used C-C bond forming methods in organic synthesis. We investigated the Michael addition of lithium propionate enolates usingMoreThe Michael addition of lithium enolates to alpha,beta-unsaturated esters is considered to be one of the powerful and widely used C-C bond forming methods in organic synthesis. We investigated the Michael addition of lithium propionate enolates using the various chiral auxiliaries to alpha,beta-unsaturated esters, methyl 2-bromo-3-methoxy acrylate and dioxinones. Various chiral propionates were prepared from the optically pure and commercially available terpenes in several steps. Michael additions using the chiral auxiliary introduced moderate to high stereoselectivities, and the factors that influence the stereoselection were examined. These results are consistent with a chelated transition state. The stereochemistry of Michael adducts was determined by the Moshers esterification and NMR experiments.-Lonomycin A, which was isolated from Streptomyces ribosidificus in 1975, is a polycyclic ether constituted of six highly functionalized rings and 23 stereocenters. Our synthetic strategy relying on the asymmetric Michael addition of lithium propionate enolate to alpha,beta-unsaturated esters introduced stereoselectively the contiguous and alternating methyl and methoxy moieties. This attractive methodology gave an easy access to the crucial intermediates in the synthetic approach towards the right-half fragment of Lonomycin A.