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Masahiro Terada

Publications and source records attributed to Masahiro Terada.

10 recordsLinked to original sources
PubMed2006

Axially chiral guanidine as highly active and enantioselective catalyst for electrophilic amination of unsymmetrically substituted 1,3-dicarbonyl compounds.

A newly designed axially chiral guanidine is found to function as an effective platform for asymmetric induction at the alpha-carbon of unsymmetrically substituted 1,3-dicarbonyl compounds. Highly efficient and enantioselective electrophilic amination of various 1,3-dicarbonyl compounds with azodicarboxylate was successfully achieved using the present chiral guanidine catalyst, which provides efficient access to the construction of nitrogen-substituted quaternary stereocenters in an optically active form.

Amination↗
PubMed2006

Axially chiral guanidine as enantioselective base catalyst for 1,4-addition reaction of 1,3-dicarbonyl compounds with conjugated nitroalkenes.

A new strategy for designing chiral guanidine molecules is presented, which features the introduction of an axially chiral binaphthyl backbone. The axially chiral guanidine catalysts thus developed facilitated the highly enantioselective 1,4-addition reaction of 1,3-dicarbonyl compounds with a broad range of conjugated nitroalkenes and showed extremely high catalytic activity.

Alkenes↗
PubMed2006

The role of neural and mechanical influences in maintaining normal fast and slow muscle properties.

The relative importance of neural and mechanical influences in maintaining normal slow and fast muscle properties remains unclear. To address this issue, we studied the effects of 10 days of hindlimb unloading (HU) with or without tenotomy and/or denervation on the cross-sectional area (CSA), myosin heavy chain (MHC) expression (immunohistochemistry) and composition (gel electrophoresis), and myonuclear number in soleus and plantaris fibers in adult male Wistar rats. In general, the adaptations in fiber type and size were similar using either single fiber gel or immunohistochemical analyses. HU resulted in atrophy of type I and I+IIa/x MHC fibers in the soleus and in type I, I+IIa/x, IIa/x, IIa/x+IIb, and IIb MHC fibers in the plantaris. Addition of tenotomy and/or denervation in HU rats had minimal effects on fiber CSA in the soleus, but fiber CSA in the plantaris further decreased, particularly in fibers expressing only fast MHCs. HU resulted in a de novo appearance of type I+IIa/x+IIb and IIa/x+IIb MHC fibers in the soleus and of type I+IIa/x+IIb MHC fibers in the plantaris. Tenotomy and/or denervation in HU rats had no further effect on the fiber type composition of either muscle. Mean myonuclear number/mm of type I fibers was decreased in the soleus of HU rats, and increased in type I and I+IIa/x fibers in HU plus tenotomy (HU+Ten) rats. In the plantaris, mean myonuclear number/mm of type IIa/x, IIa/x+IIb, and IIb fibers was lower after HU with or without tenotomy and/or denervation. Mean cytoplasmic volume/myonucleus ratio of type I and I+IIa/x fibers in the soleus of the HU group tended to be smaller than in controls. The largest decrease was noted in the HU+Ten group. In the plantaris, this ratio was unaffected by HU alone, but was decreased by addition of tenotomy and/or denervation when all fiber types were combined. These data indicate that the major cause of fiber atrophy and adaptations in myonuclear domain size in the slow soleus of HU rats is the chronic reduction in force generation, whereas the elimination of neuromuscular contact via denervation results in additional fiber atrophy and adaptations in myonuclear domain size in the fast plantaris.

Animals↗
PubMed2004

Organocatalytic asymmetric aza-Friedel-Crafts alkylation of furan.

A new asymmetric entry of the 1,2-aza-Friedel-Crafts reaction catalyzed by a chiral phosphoric acid is described. The present reaction has provided an atom-economical route to furan-2-ylamine derivatives in a highly enantioselective fashion. The synthetic utility of these products was displayed by oxidative cleavage of the furan ring (aza-Achmatowicz reaction) to form a 1,4-dicarbonyl compound that could be further derivatized to a chiral gamma-butenolid.

Journal Article↗
PubMed2004

Chiral Brønsted acid-catalyzed direct Mannich reactions via electrophilic activation.

It was found that the phosphoric acid derivatives of general structure 1 serve as highly effective catalysts for the direct addition of acetyl acetone to N-Boc-protected arylimines. The beneficial effects of the 3,3'-bisaryl substituents of the catalysts on the enantioselectivity are greatly appreciated, and thus 1d functions as an excellent catalyst. The Brønsted acid-catalyzed direct Mannich reactions presented herein provide an attractive way to construct beta-aminoketones under extremely mild conditions. The stereochemical course of this reaction was established through the synthesis of Boc-(S)-phenylglycine methylester. The transformation thus demonstrated is applicable to a useful method for the synthesis of various phenylglycine derivatives.

Journal Article↗
PubMed2002

"Asymmetric" catalysis by lanthanide complexes.

Catalysis with lanthanide (Ln) complexes has been underestimated for long time, although Ln(III) complexes have great advantages as Lewis acid catalysts for "asymmetric" carbon-carbon bond-forming reactions. Lanthanide complexes are highly active in ligand-substitution reactions, especially with hard ligands. The association with substrates and dissociation of products are achieved fast enough for high catalyst efficiency. The asymmetric catalysis of organic reactions can be greatly advanced by the use of Ln complexes with chiral ligands such as binaphthol (binol). Ln(II) complexes are good reducing agents, which can be used in a wide variety of synthetically important reactions; when chiral ligands are used, many of these reactions are highly stereoselective. In the context of "green chemistry", the development of asymmetric Ln catalysts, and their recyclable use, is of increasing importance. This review gives an overview of the most recent developments in catalysis with lanthanide(II) and lanthanide(III) complexes.

Journal Article↗