Asymmetric borane reduction of prochiral ketone using chiral bis(alpha,alpha-diphenyl-2-pyrrolidinemethanol) carbonate

Chiral bis(alpha, alpha-diphenyl-2-pyrrolidinemethanol) carbonate (DPP(2).H(2)CO(3)) is a useful asymmetric auxiliary for the asymmetric borane reduction of prochiral ketones. Chiral DPP(2).H(2)CO(3) is recoverable from the reaction and directly reusable for the reaction. The intermediate of KUR-1246, which we are developing as a new uterine relaxant, was synthesized using the methodology.     

Determination of ligand-field parameters and f-electronic structures of double-decker bis(phthalocyaninato)lanthanide complexes

The f-electronic structures of the ground states of anionic bis(phthalocyaninato)lanthanides, [Pc(2)Ln](-) (Pc = dianion of phthalocyanine, Ln = Tb(3+), Dy(3+), Ho(3+), Er(3+), Tm(3+), or Yb(3+)), are determined. Magnetic susceptibilities of the powder samples of [Pc(2)Ln]TBA (TBA = tetra-n-butylammonium cation) in the range 1.8-300 K showed characteristic temperature dependences which resulted from splittings of the ground-state multiplets. NMR signals for the two kinds of protons on the Pc rings at room temperature were shifted to lower frequency with respect to the diamagnetic Y complex in Ln = Tb, Dy, and Ho cases, and to higher frequency in Er, Tm, and Yb cases. The ratios of the paramagnetic shifts of the two positions were near constant in the six cases. This indicates that the shifts are predominantly caused by the magnetic dipolar term, which is determined by the anisotropy of the magnetic susceptibility of the lanthanide ion. Using a multidimensional nonlinear minimization algorithm, we determined a set of ligand-field parameters that reproduces both the NMR and the magnetic susceptibility data of the six complexes simultaneously. Each ligand-field parameter was assumed to be a linear function of atomic number of the lanthanide. The energies and wave functions of the sublevels of the multiplets are presented. Temperature dependences of anisotropies in the magnetic susceptibilities are theoretically predicted for the six complexes.     

Syntheses of chiral oxazolo[2,3-a]tetrahydroisoquinoline and its asymmetric alkylation. Synthesis of (S)-(−)- and (R)-(+)-sa1solidines

The isoquinolinium bromide (4), on treatment with base, underwent cyclization to give the chiral oxazolotetrahydroisoquinoline (5) with a high diastereoselectivity, which was converted to optically pure salsolidine.     

Synthesis of l,l-cycloisodityrosines by copper(II) acetate-DMAP-mediated intramolecular O-arylation of phenols with phenylboronic acids

Two types of cycloisodityrosines, 11 and 13, were synthesized from commercially available chiral tyrosine derivatives through the copper(II) acetate-DMAP-mediated diaryl ether formation of boronotyrosyltyrosines 8 and 10, respectively.     

Studies on pyrazines. Part 28 . Deoxydative acetoxylation of pyrazine N-oxides

Deoxydative acetoxylation of 3-methoxy-, 3-phenyl-, 3-methyl-, 3-chloro-, and 3-methoxycar-bonylpyrazine 1-oxides furnished predominantly 2-acetoxy-6-substituted pyrazines, some of which were more selectively prepared by addition of zinc bromide and triethylamine to the reaction. Regioselectivity of the acetoxylation is discussed based upon heat of formation by AMI and AMI-COSMO for all possible isomers of each set.     

Biosynthesis of beta-(isoxazolin-5-on-2-yl)alanine, the precursor of the neurotoxic amino acid beta-N-oxalyl-L-alpha,beta-diaminopropionic acid.

beta-(Isoxazolin-5-on-2-yl)alanine (BIA), a biosynthetic precursor of the neurotoxic amino acid beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (ODAP), was confirmed to be derived from O-acetyl-L-serine (OAS) and isoxazolin-5-one by cysteine synthase in higher plants. Some properties of this enzyme in the biosynthesis of BIA are described.     

Uncertainties and an interpretation of nonrelativistic quantum theory

We propose an interpretation of nonrelativistic quantum theory which can be considered a generalized Copenhagen interpretation. The uncertainties (i.e., q and p) in Heisenberg's uncertainty relation q · p/2 can be characterized as (average) errors in an approximate simultaneous measurement if the interpretation proposed here is accepted in nonrelativistic quantum mechanics. Under this interpretation, the (discrete) trajectory of a particle (like Wilson chamber) is significant enough. We propose to analyze this trajectory numerically.     

Bismuth triflate-chiral bipyridine complexes as water-compatible chiral Lewis acids

[reaction: see text] Catalytic asymmetric hydroxymethylation of silicon enolates with an aqueous formaldehyde solution has been developed using a chiral bismuth complex. This is the first example of highly enantioselective reactions using a chiral bismuth catalyst in aqueous media. In this paper, we have added Bi(OTf)(3)-1 complex as a "water-compatible Lewis acid". Bi(OTf)3 is unstable in the presence of water but is stabilized by the basic ligand.     

Photolysis of polymeric organosilicon systems. III. Synthesis and photochemical behavior of polysiloxanes containing phenyldisilanyl units

The synthesis and photochemical behavior of three types of polysiloxanes containing phenyldisilanyl units as chromophore have been reported. Irradiation of thin liquid films of the polymer (2) prepared from copolymerization of octamethylcyclotetrasiloxane and 1,3,5-triphenyl-1,3,5-tris(trimethylsilyl)cyclostrisiloxane (1) with a 500-W Xe-Hg lamp afforded transparent solid films which are insoluble in common organic solvents. Similar irradiation of thin liquid films of polysiloxane (8) containing both phenyldisilanyl units and vinyl groups resulted in formation of crosslinked solid films. When thick films of the polymers 2 and 8 were irradiated with a Xe-Hg lamp, crosslinking occurred only on the surface of the films, but inside remained as liquid. Irradiation of the films prepared from the polysiloxane involving the phenyldisilanyl units and butenyl groups, however, gave crosslinked solid films, whatever thickness of the films. The mechanism of photochemically induced crosslinking of the copolymers is discussed on the basis of the results obtained from the photolysis of 1,1-bis(trimethylsiloxy)-1-phenyl(trimethyl)disilane as a model compound.