Hiroaki Sasai

Enantioselective synthesis of α-hydroxy phosphonates using the LaLi3tris(binaphthoxide) catalyst (LLB), prepared by an improved method

Abstract LaLi 3 tris(binaphthoxide) catalyst (LLB), which is prepared from LaCl 3 ·7H 2 O (1 mol equiv), ( R )- or ( S )-BINOL dilithium salt (2.7 mol equiv), and NaO- t -Bu (0.3 mol equiv), is effective for the hydrophosphonylation of various aldehydes to give desired α-hydroxyphosphonates in up to 95% ee (88% yield). It is also noteworthy that with slow addition of the aldehydes the enantiomeric excesses of the products were increased.

Catalytic asymmetric nitroaldol reaction: An efficient synthesis of (S) propranolol using the lanthanum binaphthol complex

Abstract ( S ) Propranolol, a more potent optical isomer of the widely used β-blocker, was conveniently synthesized in a higly enantioselective manner by the lanthanum-( R )-(+)-binaphthol complex catalyzed asymmetric nitroaldol reaction.

Catalytic asymmetric nitroaldol reactions. A new practical method for the preparation of the optically active lanthanum complex

Abstract The optically active La complex, which catalyzes asymmetric nitroaldol reactions, was found to be readily prepared from LaCl3·7H2 O. The presence of water, LiCl or LiBr and an alkali metal hydroxide was essential for the formation of the effective lanthanum binaphthoxide complex.

Diastereoselective catalytic asymmetric nitroaldol reaction utilizing rare earth-Li-(R)-BINOL complex. A highly efficient synthesis of norstatine

Abstract Rare earth-Li-BINOL complexes were used to catalyze nitroaldol reactions of optically active α-amino-aldehydes with nitromethane in a highly diastereoselective manner. A typical adduct, (2S, 3S)-3-phthaloylamino-2-hydroxy-1-nitro-4-phenylbutane was conveniently converted to (2S, 3S)-3-amino-2-hydroxy-4-phenylbutanoic acid (erythro-AHPA ; phenylnorstatine), a component of the HIV protease inhibitor KNI-227 and KNI-272.

Catalytic asymmetric Michael reactions promoted by the La-Na-BINOL complex (LSB). Enantioface selection on Michael donors

Abstract LSB can efficiently promote catalytic asymmetric Michael reactions in CH2Cl2, inducing high enantiomeric excesses on the Micheal donor side. The multifunctional character of LSB appears to give rise to high stereoselectivity, offering the most efficient asymmetric reaction of its type.

Effects of rare earth metals on the catalytic asymmetric nitroaldol reaction

Abstract Various asymmetric rare earth complexes have been prepared from rare earth metal trichlorides such as YCl 3 , LaCl 3 , PrCl 3 , NdCl 3 , SmCl 3 , EuCl 3 , GdCl 3 , TbCl 3 and YbCl 3 , dilithium ( R ) binaphthoxide, NaOH and H 2 O. The optical purities of nitroaldols obtained using these rare earth complexes as an asymmetric catalyst have been highly dependent on the size of rare earth metals. The application to a catalytic asymmetric synthesis of ( S )-metoprolol, a β 1 -selective β-blocker, has been also achieved.

Catalytic asymmetric Michael addition of nitromethane to enones controlled by (R)-LPB

Abstract The multifunctional catalyst LPB controls the Michael addition of nitromethane to chalcones with ≥95% ee.

Syntheses of (S)-(−)-pindolol and [3′-13C]-(R)-(−)-pindolol utilizing a lanthanum-lithium-(R)-BINOL ((R)-LLB) catalyzed nitroaldol reaction

Abstract An efficient synthesis of (−)-pindolol, an effective β-blocker, has been achieved utilizing a lanthanum-lithium-( R )-BINOL (( R )-LLB) catalyzed nitroaldol reaction as a key step. This methodology was applicable to a synthesis of 13 C-labeled (−)-pindolol, which would be useful as a biological tool for tracing the metabolism of β-blocker and 5-HT 1A receptor antagonist. The mechanistic aspects of the LLB catalyzed nitroaldol reaction are also discussed.

First catalytic asymmetric hydrophosphonylation of cyclic imines: Highly efficient enantioselective approach to a 4-thiazolidinylphosphonate via chiral titanium and lanthanoid catalysts

The catalytic and enantioselective hydrophosphonylation of a cyclic imine, namely the 3-thiazoline 1, is described. We have discovered a highly efficient enantioselective de novo approach to the pharmaceutically interesting 4-thiazolidinylphosphonate 2 using either titanium or lanthanoid chiral catalysts, which gives excellent enantiomeric purities (up to 98 %ee) and high chemical yields.

Catalytic asymmetric nitroaldol reaction of α,α-difluoro aldehydes mediated by rare earth-lithium-BINOL complexes

Rare earth-Li-BINOL complexes were used to catalyze nitroaldol reactions of α,α-difluoro adehydes with nitromethane in a good enantioselective manner. The optical yields of nitroaldol 2a depend on the size of rare earth metals, and an Sm-Li-BINOL complex gave the highest enantioselectivity. The enantiotopic face selection of α,α-difluoro aldehyde 1a was found to be different from that of nonfluorinated aldehydes employed in the usual catalytic asymmetric nitroaldol reactions.