| Budget Amount *help |
¥7,000,000 (Direct Cost: ¥7,000,000)
Fiscal Year 1992: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1991: ¥4,900,000 (Direct Cost: ¥4,900,000)
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| Research Abstract |
In our studies on the development of new efficient ligands for catalytic asymmetric hydrogenations, we proposed the "respective control concept", and reported the syntheses and applications of efficient chiral bisphosphine ligands such as BPPM (and its analogs), BCPM (and its analogs), and MOD-DIOP, the rhodium(I) complexes of which showed excellent enantioselectivity as well as high catalytic activity. The ligands have both an electron-rich phosphine and a diarylphosphine. The former phosphine and the latter one have functions of increasing catalytic activity and showing high enantioselectivity, respectively, in the rhodium(I)-catalyzed asymmetric hydrogenations. Among th e ligands, BCPM and BPPM (and their analogs) showed high efficiency in the asymmetric hydrogenations of prochiral ketones and unsaturated carboxylic acids, yielding optically active aminoalchols and carboxylic acids. MOD-DIOP was found to be a very effective ligand in the rhodium(I)-catalyzed asymmetric hydrogenation of unsaturated carboxylic acids, itaconic acid and its derivatives. Itaconic acid half-ester derivatives were hydrogenated in high enantioselectivity, and the products were easily converted to optically pure gamma-lactones, which were the useful key intermediates for the synthesis of naturally occurring lignan lactones including podophyllotoxin and its derivatives. Deoxypodophyllotoxin was synthesized via several steps from the key intermediate. Deoxypodophyllotoxin is microbially convertible to podophyllotoxin, which is a useful intermediate for the synthesis of anti-cancer drugs, etoposide and teniposide. Next, new axially unsymmetric bisphosphine ligands, BIMOP and its analog, were synthesized and found to be effective for rhodium(I)- and ruthenium(II)-catalyzed asymmetric hydrogenations of unsaturated carboxylic acids. The reactions can be employed for the synthesis of deoxypodophyllotoxin. Some other ligands were also developed for related asymmetric hydrogenations.
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