| Budget Amount *help |
¥4,120,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥420,000)
Fiscal Year 2007: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
Fiscal Year 2006: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
Chiral quaternary ammonium cations being capable of recognizing a substrate through non-bonding interaction and regulating the position of counterion have been newly designed and prepared. These ammonium salts bearing a stereochemically defined tetranaphthyl backbone act as efficient, dual-functioning chiral phase-transfer catalysts, which enable the highly enantioselective Strecker reaction of various aliphatic aldimines under toluene-aqueous potassium cyanide biphasic conditions. In general, 1 mol% of the catalyst with 1.5 equivalents of KCN was sufficient for the smooth reaction, and the corresponding protected amino nitrile was obtained uniformly in high yield with excellent enantioselectivity. Emphasized is the fact that this system nicely accommodates the substrates having α-tertalkyl substituents such as pivalaldimine, thereby enabling a facile synthesis of enantiomerically enriched tertleucine and its various analogues, a series of considerably useful chiral building blocks net
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accessible by the asymmetric alkylation of glycine derivatives. The new asymmetric Strecker protocol thus developed, however, had a drawback: the chemical yield and enantioselectivity were still insufficient in the reactions with secondary and, particularly, primary alkyl aldimines compared to tertiary alkyl ones. We reasoned that it could be ascribed to the partial imine hydrolysis and uncatalyzed cyanation under biphasic conditions lb overcome these problems associated with the direct use of the reactive sulfonyl imines, highly efficient, enantioselective synthesis of N-protected α-amine nitriles from the corresponding α-amino sulfones through the in situ generation of the reactive imines under similar biphasic conditions has also been achieved, Maturing its practical advantages. Meanwhile, we have been pursuing new approach toward the utilization of chiral quaternary ammonium salts as a homogeneous, organic molecular catalyst Quite recently, we have designed a new chiral ammonium betaine having tetranaphthyl framework, and its unique catalytic activity has been uncovered. This seems to be our important, ongoing research subject. Less
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