| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
The lipase-catalyzed organic syntheses have been gaining increased attention as environmentally benign processes recently. However, their use has been limited mainly for the preparation of optically active compounds via the kinetic resolution of racemic alcohols, and their application to the construction of carbon skeleton are few. Recently, we disclosed the first domino-type asymmetric synthesis, in which the lipase-catalyzed kinetic resolution of racemic alcohols with functionalized ethoxyvinyl esters was followed by the intramolecular cycloaddition reaction of the resulting optically active esters to directly give polycyclic compounds. We also developed some ruthenium complexes that effectively catalyze the racemization of optically active alcohols at room temperature. The combination of the ruthenium complexes and lipases have achieved the first domino-type synthesis accompanied by a dynamic kinetic resolution (DKR). This project has aimed at the practical expansion of this domino-
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type synthetic methodology. The followings are summary of the results:
1. A novel DKR of secondary allyl alcohols has been developed by the combined use of the oxovanadium compound, VO(OSiPh_3)_3, and the lipases to give optically active allyl esters (88-99% ee) in 69-99% isolated yields. This method features the unique racemization process through the vanadium-catalyzed 1,3-transposition of the allyl alcohols.
2. The developed racemization enabled an unprecedented DKR of the tertiary allyl alcohols with the migration to give the same products with better optical purity; viz., 99% ee, in most cases. These results have shown that the structural isomers of two kinds of allyl alcohols can be equally employed for this DKR and offer a new convenient strategy for the asymmetric synthesis of optically pure allyl acetates. The application of these methods to the allyl alcohols having a diene moiety is now under study in our laboratory, which is expected to construct the carbon skeleton via the domino-type process.
3. Studies for the development of more potent metal catalysts to accelerate the above-mentioned racemization process have been carried out, and some molybdenum compounds were discovered as potential candidates. Less
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