Direct synthesis of 1,3-diketones by Rh-catalyzed reductive alpha-acylation of enones

1,3-Diketones were synthesized from alpha,beta-unsaturated ketones by treatment with acid chlorides and Et(2)Zn in the presence of RhCl(PPh(3))3. This is a very simple and extremely chemoselective reaction to give the adduct at the alpha-position of alpha,beta-unsaturated ketones.     

Tailoring D‐Amino Acid Oxidase from the Pig Kidney to R‐Stereoselective Amine Oxidase and its Use in the Deracemization of α‐Methylbenzylamine

The deracemization of racemic amines to yield enantioenriched amines using S‐stereoselective amine oxidases (AOx) has recently been attracting attention. However, R‐stereoselective AOx that are suitable for deracemization have not yet been identified. An R‐stereoselective AOx was now evolved from porcine kidney D ‐amino acid oxidase (pkDAO) and subsequently use for the deracemization of racemic amines. The engineered pkDAO, which was obtained by directed evolution, displayed a markedly changed substrate specificity towards R amines. The mutant enzyme exhibited a high preference towards the substrate α‐methylbenzylamine and was used to synthesize the S amine through deracemization. The findings of this study indicate that further investigations on the structure–activity relationship of AOx are warranted and also provide a new method for biotransformations in organic synthesis.     

Artificial model for cystathionine β-synthase: efficient β-replacement reaction with thiols employing a novel pyridoxal model compound having an imidazole function

As a second-generation pyridoxal model compound for cystathionine β-synthase, we designed a novel model compound having an ionophore function and an imidazole function, application of which to the β-replacement reaction with various thiols smoothly took place to give S-substituted cysteines. Peptides having a serine-O-carbonate residue at the N-terminal position were also converted to the corresponding peptides having an S-substituted cysteine residue under the catalytic conditions of the novel pyridoxal model compound.     

Dihydrogen activation by sulfido-bridged dinuclear Ru/Ge complexes: insight into the [NiFe] hydrogenase unready state

A S/SH bridged hetero-dinuclear Ru/Ge complex cation reacted with H(2) to afford the μ-S/μ-H complex. The reaction was considerably slower compared to that of the μ-S/μ-OH complex. Thus, the μ-S/μ-SH and μ-S/μ-OH complexes might provide models for the unready and ready states, respectively, of [NiFe] hydrogenase.     

Controllable photoinduced optical attenuation in a single-mode optical fiber by irradiation of a femtosecond pulse laser

Novel optical attenuation fibers were fabricated by the irradiation of a focused infrared femtosecond pulsed laser onto the core of a silica glass single-mode optical fiber. Optical attenuation at a wavelength of 1.55 microm proportionally increased with increasing numbers of irradiation points and was controllable under laser irradiation conditions. The single-mode property of the waveguide and the mode-field diameter of the optical fiber were maintained after irradiation of the femtosecond laser. It is suggested that the attenuation results from optical scattering at photoinduced spots formed inside the fiber core.     

Synthesis of syn‐2,4‐Dimercapto‐1,3,2,4‐dithiadigermetane and Its Application to Ge2PdS4 Cluster Synthesis

The sulfurization of DmpGeH₃ (Dmp=2,6‐dimesitylphenyl) afforded the trinuclear germanium sulfide [DmpGe(μ‐S)]₂(μ‐S)₂Ge(SH)‐Dmp and a series of polythiadigermabicyclo[x.1.1]alkanes (x=3, 4, 5). The reduction of the S? S bonds of these germabicycloalkanes by NaBH₄ at 0 °C afforded the dinuclear mercaptogermane syn‐[DmpGe(SH)(μ‐S)₂Ge(SH)‐Dmp] ( 5 ) in good yield. The reaction of [Pd(dppe)Cl₂] (dppe=1,2‐bis(diphenylphosphanyl)ethane) and the dilithium salt of 5 prepared in situ by the addition of nBuLi (2 equiv) gave the Ge₂PdS₄ cluster [DmpGe(μ‐S)]₂[(μ‐S)₂Pd(dppe)], in which the dithiadigermetanedithiolate is bound to the Pd atom at the two thiolato sulfur atoms. The same reaction with [Pd(PPh₃)₂Cl₂] gave another Ge₂PdS₄ cluster, [DmpGe(μ‐S)]₂[(μ‐S)₂Pd(PPh₃)], but with the dithiadigermetanedithiolate and the Pd center conjoined through a μ‐S atom between the two germanium atoms in addition to the two thiolato sulfur atoms to form a highly distorted cluster core. The formation of two different types of Ge₂PdS₄ clusters represents the usefulness of 5 in the synthesis of various polynuclear complexes composed of germanium and transition metals.     

A convenient synthesis of the beraprost intermediate: a useful method for introducing a C3 unit at the benzyl position

[reaction: see text] The Heck reaction is a more efficient and reliable method than previous ones for introducing a C3 unit at the benzyl position for the synthesis of Beraprost. Especially, trialkylated long-chain amines such as (n-C(8)H(17))(3)N and (n-C(12)H(25))(3)N resulted in good yields. This development will be used for the industrial synthesis of Beraprost.     

Nonlinear Sigma Models in (1+2) Dimensions and an Infinite Number of Conserved Currents

In this Letter, we treat nonlinear sigma models such as the C P¹-model, Q P¹-model, etc. in 1+2 dimensions. For submodels of such models, we definitely construct an infinite number of nontrivial conserved currents. Our result is a generalization of Alvarez, Ferreira and Guillen.