Development of Novel Asymmetric Synthetic Reactions

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1. Asymmetric Alkylation Reactions via Chiral Chelated IntermediatesExaminations were made on the asymmetric alkylation reactions based on the concept of fixing the reactive conformation by chelation. It is shown that this concept is applicable successfully to the asymmetric Michael reaction. Thus, chiral chelated lithioenamines were prepared by condensation of L-valine ester and <beta> -keto esters followed by metalation. The reaction of these lithioenamines with di-tert-butyl methylenemalonate afforded, after hydrolysis, both enantiomers of the corresponding Michael adducts, depending on the combination of solvents and additives used. This strategy was found to be applicable also to the enantioselective asymmetric Michael reaction.2. Asymmetric Alkylation Reaction using Optically Active Butyrolactone and ButyrolactamBoth enantiomers of <gamma> -hydroxymethyl- <gamma> -butyrolactone were found to be prepared easily and in quantity from inexpensive L-glutamic acid, and were found to be … More useful chiral synthons for the asymmetric synthesis of antileukemic natural products, such as megaphone and spatol. In the course of the above synthetic efforts, it has become clear that the corresponding <gamma> -hydroxymethyl- <gamma> -butyrolactam, also prepared in optically pure form from L-glutamic acid, is a highly useful chiral reagent in asymmetric synthesis due to its unusual conformation. Novel method for the diastereoselective asymmetric synthesis of <beta> -substituted carboxylic acids using this lactam was developed.3. Enantioselective Asymmetric Synthesis using Chiral Lewis Acids and Chiral BasesEnantioselective Diels-Alder reaction catalyzed by optically active alkoxyaluminum dichlorides as chiral Lewis acids was further developed. Enantioselective deprotonation reaction of prochiral cyclic carbonyl compounds having <sigma> -plane in their molecules was realized by using chiral lithium amide bases. The products were isolated as trimethylsilyl enol ethers, which are chemically equicalent to enolate anions. This method should be applicable widely for the synthesis of various chiral synthons. Some mechanistic explanations of this reaction were proposed. Less