| Research Abstract |
Chiral half esters, derived from monoalkymalonic acid and chiral alcohol, gave rise to the crystallization induced asymmetric transformation to afford exclusively one diastereoisomer. Thus, versatile chiral building blocks, unsymmetrical 1, 3-propanediol derivatives, having a tertiary stereogenic center, were enantioselectively prepared. Taking advantage of the chiral building blocks, 1beta-methylcarbapenem, emetine, protoemetine, protoemetinol, tubulosine, dihydrocorynantheol, dihydroantirhine and dihydrocinchonine were enentioselectively synthesized.
Alkylation of the chiral half esters in the presence of lithium hexamethyldisilazide constructed the quaternary stereogenic center in a diastereoselective manner. Thus, a general synthetic method for the quaternary chiral building blocks has been developed. Exploiting this strategy, alpha-alkyl alpha-amino acids and Hunteria and Aspidosperma type indole alkaloids were synthesized in optically pure forms. Furthermore, the enantioselective assembly of quatemary stereogenic centers possessing a fluorine atom was achieved by the application of the above methodology.
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