Concise synthesis of indole-fused 1,4-diazepines through copper(I)-catalyzed domino three-component coupling-cyclization-N-arylation under microwave irradiation

Indole-fused benzo-1,4-diazepines were synthesized by copper-catalyzed domino three-component coupling-indole formation- N-arylation under microwave irradiation from a simple N-mesyl-2-ethynylaniline. This method was also applicable to the formation of heterocycle-fused 1,4-diazepines.     

Direct construction of bicyclic heterocycles by palladium-catalyzed domino cyclization of propargyl bromides

The palladium-catalyzed domino cyclization of propargyl bromides having two nucleophilic functional groups is described. Treatment of 1,7-diamino-5-bromohept-3-yne derivatives with catalytic Pd(PPh3)4 in the presence of NaH in MeOH gives the 2,7-diazabicyclo[4.3.0]non-5-enes in good yields. Interestingly, the regioselectivity of the reaction is completely controlled by the relative reactivity of the amine functional groups, irrespective of the position of the nucleophiles. The malonate derivative also undergoes domino cyclization to produce a hexahydroindole derivative.     

Molecular Design for Reversing the Photoswitching Mode of Turning ON and OFF DNA Hybridization

A new photoswitch for DNA hybridization involving para‐substituted azobenzenes (such as isopropyl‐ or tert‐butyl‐substituted derivatives) with L ‐threoninol as a linker was synthesized. Irradiation of the modified DNA with visible light led to dissociation of the duplex owing to the destabilization effect of the bulky substituent on the trans‐azobenzene. In contrast, trans‐to‐cis isomerization (UV light irradiation) facilitated duplex formation. The direction of this photoswitching mode was entirely reversed relative to the previous system with an unmodified azobenzene on D ‐threoninol whose trans form turned on the hybridization, and cis form turned it off. Such reversed and reversible photoswitching of DNA hybridization was directly demonstrated by using fluorophore‐ and quencher‐attached oligonucleotides. Furthermore, it was revealed that the cis‐to‐trans thermal isomerization was greatly suppressed in the presence of the complementary strand owing to the formation of the more‐stable duplex in the cis form.     

Palladium-catalysed biscyclisation of allenic bromoalkenes through a zipper-mode cascade

Treatment of allenic bromoalkenes bearing a nucleophilic moiety with a catalytic amount of palladium(0) in the presence of TBAF or Cs(2)CO(3) in MeCN affords bicyclic heterocycles in good to high yields, through zipper-mode cascade cyclisation.     

Context-dependent fluorescence detection of a phosphorylated tyrosine residue by a ribonucleopeptide

Tools for selective recognition and sensing of specific phosphorylated tyrosine residues on the protein surface are essential for understanding signal transduction cascades in the cell. A stable complex of RNA and peptide, a ribonucleopeptide (RNP), provides effective approaches to tailor RNP receptors and fluorescent RNP sensors for small molecules. In vitro selection of an RNA-derived pool of RNP afforded RNP receptors specific for a phosphotyrosine residue within a defined amino-acid sequence Gly-Tyr-Ser-Arg. The RNP receptor for the specific phosphotyrosine residue was successfully converted to a fluorescent RNP sensor for sequence-specific recognition of a phosphorylated tyrosine by screening a pool of fluorescent phosphotyrosine-binding RNPs generated by a combination of the RNA subunits of phosphotyrosine-binding RNPs and various fluorophore-modified peptide subunits. The phosphotyrosine-binding RNP receptor and fluorescent RNP sensor constructed from the RNP receptor not only discriminated phosphotyrosine against tyrosine, phosphoserine, or phosphothreonine, but also showed specific recognition of amino acid residues surrounding the phosphotyrosine residue. A fluorescent RNP sensor for one of the tyrosine phosphorylation sites of p100 coactivator showed a binding affinity to the target site ~95-fold higher than the other tyrosine phosphorylation site. The fluorescent RNP sensor has an ability to function as a specific fluorescent sensor for the phosphorylated tyrosine residue within a defined amino-acid sequence in HeLa cell extracts.     

Crystal structure of friction-transferred poly(2,5-dioctyloxy-1,4-phenylenevinylene)

Poly(2,5-dioctyloxy-1,4-phenylenevinylene) (DOPPV) was found to form a highly oriented film by a friction-transfer technique. Structural investigation of friction-transferred DOPPV was studied by means of polarized ultraviolet-visible (UV-vis) absorption spectroscopy, polarized photoluminescence (PL) spectroscopy, and synchrotron-sourced grazing incident X-ray diffraction (GIXD) analysis. The polarized UV-vis absorption and PL spectra indicate clear axial alignment. DOPPV backbones in friction-transferred film are highly aligned along the drawing direction of the friction-transfer. Further information of the molecular arrangement in friction-transferred DOPPV film was investigated by both the out-of-plane and the in-plane GIXD analyses with synchrotron source. The DOPPV molecules in friction-transferred films were perfectly arranged three-dimensionally: the backbones aligned along the drawing direction of friction-transfer, the alkyl side chains lay in the film plane, and the planar backbones were arranged parallel to the film surface. Additionally, two neighboring DOPPV molecules along the direction of inter-backbones separation by alkyl side chains were found to be shifted with respect to one another by the mean distance of half of a monomeric repeat.     

Application of High Polymers in Extracorporeal Blood Treatment

Applications of high polymers, especially conventional polymers used in an extracorporeal blood purification system, are discussed through the development of an LDL (low-density lipoprotein) apheresis system. An adsorption-based blood purification system designed to remove LDL selectively (a major risk factor leading to severe heart disease) was developed using dextransulfate as the specific ligand to adsorb LDL. Dextransulfate, in order to give a novel function similar to that of an LDL receptor, was covalently bound to porous cellulose beads with optimized morphology. The sophisticated function of an LDL receptor was successfully mimicked by the appropriate combination of well-defined conventional polymers, namely dextransulfate and cellulose. A total apheresis system, including a plasma separator, was also designed solely utilizing high polymers. This enabled the total system to be disposable, ensuring reliability. High polymers used in the system were all conventional polymers, those already qualified and evaluated for medical use. In designing this new blood purification system, our approach was to employ many of the conventional and qualified polymers, leading to a system industrially manufacturable, reliable and accepted as standard treatment in the medical community. This system demonstrated efficacy for the treatment of familial hypercholesterolemia, and is widely used in the world as standard treatment. © 1997 John Wiley & Sons, Ltd.     

Reaction of the acetals with TESOTf-base combination; speculation of the intermediates and efficient mixed acetal formation

We report here unexpected highly chemoselective deprotection of the acetals from aldehydes. Treatment of acetal compounds from aldehydes with TESOTf-2,6-lutidine or TESOTf-2,4,6-collidine in CH2Cl2 at 0 degrees C followed by H2O workup at the same temperature caused the conversion of the acetal functions to aldehyde functions. The reaction had generality and was applied to many acetal compounds. Study using various bases revealed the reaction and reached the best combination of TESOTf-base. It was very mild and highly chemoselective and proceeded under weakly basic conditions. Then, many functional groups such as allyl alcohol, silyl ether, acetate, methyl ether, triphenylmethyl (Tr) ether, 1,3-dithiolane, methyl ester, and tert-butyl ester could survive under these conditions. Furthermore, this methodology could selectively deprotect the acetals in the presence of ketals as the most characteristic feature, although this chemoselectivity is difficult to achieve by other previously reported methods. A detailed study of the reaction including MS and NMR studies revealed the reaction mechanism for determining the structures of the intermediates, pyridinium-type salts. These intermediates had a weak electrophilicity and were successfully applied to the efficient formation of the mixed acetals in high yields.     

Stereoselective synthesis of (Z)-alkene-containing proline dipeptide mimetics

In peptides and proteins, the peptide bond between an amino acid and proline exists as an equilibrium mixture of the cis-imide and trans-imide due to the low energy barrier in their interconversion. This feature greatly influences the structure and function of the proline-containing peptides and proteins. Therefore, restricting the amide bond with an (E)- or (Z)-alkene should provide a promising method for elucidating the structure-activity relationships of the peptide and the proteins. In this report, the regio- and stereoselective synthesis of cis-alanylproline (Ala-Pro) type (Z)-alkene dipeptide mimetic is described. The key steps of this synthesis are to introduce a C3 unit onto a gamma-phosphoryloxy-alpha,beta-unsaturated-delta-lactam with an organocopper-mediated anti-S(N)2' reaction and subsequently construct a five-membered proline-like cyclic structure with an intramolecular Suzuki coupling reaction. Hydrolysis of the amide bond in the resulting bicyclic lactam yields the desired cis-Ala-Pro type (Z)-alkene dipeptide isostere. The presented synthetic methodology should be applicable to the general syntheses of other cis-aminoacylproline type (Z)-alkene dipeptide mimetics.