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Polysaccharide analogues having 2-deoxypsicofuranose as a repeating unit are successfully synthesized by ring-opening metathesis polymerization of 7-oxanorbornene-2,3-diol and dihydroxylation.

Exactly defined number of gear-shaped amphiphiles self-assemble into discrete aggregates. In water (or aqueous methanol) these amphiphiles mesh each other so as to reduce indented hydrophobic surface area exposed to the solvent, leading to 2 nm-sized cubic-shaped hexamers. Furthermore, tetrahedron-shaped tetramers are constructed from four gear-shaped amphiphiles and a guest molecule with the aid of van der Waals interaction between the amphiphiles and the guest molecule.

Although Ito-Saegusa oxidation gives defined α,β-unsaturated ketones from silyl enol ether of ketones, controlled by the position of the sp2 carbon of the silyl enol ether, the formation of a regioisomeric product that is oxidized abnormally is observed.

Based on the synthesis of both enantiomers and spectroscopic comparison it is found that the natural compound is represented by (-)-I and not by (+)-I as was previously reported.

Surface alloying with rhenium was performed on a molybdenum single-crystal sheet using an electron beam of high power density. A number of large pores formed along the weld bond. However, no definite grain boundaries were recognized by either optical microscopy or X-ray back-Laue photography. The residual content of rhenium in the fused zone was about 38 wt.% and consequently hardening occurred.

The gas‐phase equilibria of the clustering reaction (C6H6)+n−1+C6H6 =(C6H6)+n were studied with a pulsed electron‐beam high‐pressure mass spectrometer. The enthalpy changes −ΔH0n−1,n for the reaction with n=2–4 were determined to be 20.6±1.0, 7.8±0.5, and ∼7 kcal/mol, respectively. The structure of dimer cation (C6H6)+2 was determined by ab initio spin‐restricted open‐shell Hartree–Fock molecular orbital (ROHF MO) calculations. Two isomers, ‘‘axial C2 ’’ and ‘‘parallel C2v, ’’ are calculated to be located at the potential‐energy minima. The axial C2 is 3.0 kcal/mol more stable than the parallel C2v by ROHF/6‐31G**//ROHF/3‐21G.

Subgrain boundaries were removed from LaB6 crystals prepared by the floating zone method, by adding the rare earth hexaborides CeB6, PrB6 and NdB6. In this work the thermionic emission properties of cathodes made from the boundary-free crystals were examined and compared with those of an LaB6 crystal cathode. Addition of the rare earth borides did not influence the emission properties (emission current density, brightness and life) under practical working conditions.

Irradiation of the title compounds Ar(CH2)nNHPh (Ar = 10-bromo-9-phenanthryl, n= 3, 4, 5, 6, 10) gave debrominated aniline derivatives in all cases. For n= 3 and 4, the cyclic compounds 4a,b were isolated in moderate yields. A photo-induced electron-transfer mechanism is proposed.

Selective monodesilylation of 1,8-bis(t-butyldiphenylsilyl)-1,3,5,7-octatetrayne and 1,6-bis(t-butyldiphenylsilyl)-1,3,5-hexatriyne with lithiated phenylacetylene gave unstable 1-(t-butyldiphenylsi...

(S)-1-Phenylethylamine has been used as a chiral auxiliary as well as a nitrogen atom donor in the synthesis of an enantiomeric pair of azetidine-2,4-dicarboxylic acids, the absolute configuration of one of which has been assigned on the basis of the X-ray structure and the known absolute configuration of the (S)-1-phenylethylamine moiety. Chiral auxiliaries of related C2-symmetric azetidines have also been prepared and their propionamides have been asymmetrically alkylated. The stereochemistry of the resulting products was compared with their analogues having different ring sizes.

A new route for the asymmetric construction of quaternary carbon centres containing a trifluoromethyl group has been established using a highly regio- and stereo-selective S N 2′ reaction of organocopper and organocuprate reagents with allylic mesylates 4 and 8.

Chiral aldol structures with fluorine modifications on a methyl group have been realized by utilization of the relatively rigid cyclic intermediates from the very common chiral pool compound, d -glucose, leading to attainment of the high diastereoselectivities as well as construction of differently fluorinated target materials from a single intermediate.

The Dy endohedral C60 (Dy@C60) was extracted with aniline under ultrasonic irradiation from the soot prepared by arc-heating of Dy2O3/graphite composite rod under He pressure of 80 Torr. The purification of Dy@C60 was performed by using high performance liquid chromatography (HPLC) technique. Furthermore, the Dy endohedral C82 (Dy@C82) was effectively extracted from the soot with N,N-dimethylformamide (DMF).

The resolution of racemic 1-(2-pyridyl)ethanols 2a-n, including the 2,2'-bipyridyl and isoquinolyl derivatives, by lipase-catalyzed asymmetric acetylation with vinyl acetate is reported. The reactions were carried out in diisopropyl ether at either room temperature or 60 degrees C using Candida antarctica lipase (CAL) to give (R)-acetate and unreacted (S)-alcohol with excellent enantiomeric purities in good yields. The reaction rate was relatively slow at room temperature for substrates bearing an sp(3)-type carbon at the 6-position on the pyridine ring, such as 2c, 2d, and 2e, and for those bearing 1-hydroxypropyl and allyl groups at the 2-position on the pyridine ring, such as 2l and 2m. In such cases, a higher temperature was required. Thus, when the reaction was conducted at 60 degrees C, it was accelerated 3- to 7-fold without losing the high enantiospecificity. However, the reaction of homoallylic alcohol 2n was not complete, even when the reaction was continued for a longer period of time at 60 degrees C. This enzymatic resolution can be used practically in a wide range of reaction scales from 10 mg to 10 g or more. This catalyst can be used repeatedly with a 5-10% loss of the initial activity with each use.

A new series of acyclic podands was designed so that three pyridine moieties cooperatively bind a guest Ag+. Liquid−liquid extraction, NMR binding, and computer calculation experiments reveal that podands with three pyridine donors in a proper geometry exhibit a perfect Ag+ specificity. They selectively extracted Ag+ in the presence of equimolar Pb2+, Cu2+, Ni2+, Co2+, and Zn2+. Introduction of two chiral centers close to the pyridine binding sites surprisingly influences the Ag+-binding ability of the podand. Fourteen new pyridine podands were evaluated as carriers in a liquid membrane transport system. A combination of ligand geometry and stereocontrolled substitution provides excellent Ag+-specific transport.

In expectation of discovering their antiviral activity, acyclic adenosine derivatives 7, 11, 12, and 16 were designed as analogs of neplanocin A (NPA) and L-eritadenine which are strong inhibitors of S-adenosyl-L-homocysteine hydrolase. The 1′,5′-seco-analog of 4′-deoxymethyl-NPA (DHCA) 7 was synthesized by dideoxygenation of 9-(2,3-O-isopropylidene-D-ribityl)adenine (2). Acyclic DHCA analogs 11 and 16 were obtained by Wittig reaction of the aldehyde 3 with Ph3P=CHCO2Et and Ph3P=CHCN, respectively. Hydrolysis of the ester 11 afforded a vinylog of L-eritadenine 12. The synthesized acyclic nucleosides 7, 10, and 11 were evaluated for antiviral activity, however, none of them showed any significant antiviral activity.

Photoswitching of the enzymatic activity of ribonuclease S′ was successfully carried out by site specific incorporation of phenylazophenylalanine into S-peptide skeleton by semisynthesis.

Enantioselective total synthesis of (+)-isoboonein, an iridoid lactone, was accomplished from (-)-dimenthyl bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylate, which was synthesized by diastereoselective Diels-Alder reaction of dimenthyl fumarate with cyclopentadiene.

Potassium aeshynomate (1) was isolated as an leaf-opening substance of the nyctinastic plant, Aeshynomene indica L. Compound 1 was quite effective for the leaf-opening of A.indica at 1×10−3 M, and was found to be a new type of leaf-movement factor containing a novel γ-amino acid moiety.

Fluoro-benzeneselenenylation of electron-deficient alkenes with benzeneselenenyl fluoride [PhSeF] generated in situ by the reaction of diphenyl diselenide and xenon difluoride proceeded smoothly in dichloromethane. The product yields increased remarkably in higher concentration of the seleno-reagent. The reactive seleno-reagent PhSeF may be stabilized in the higher concentration presumably by the favorable association of the reagent.

For simultaneous construction of a polyether backbone and the allenyl side chains, Lewis acid-catalyzed three-component condensation reactions of aldehydes, alkoxytrimethylsilanes, and 1-trimethylsilyl-2-butyne were studied. The reaction of these three compounds took place in the presence of a catalytic amount of TrClO4 at −78°C to yield the corresponding α-allenyl ethers in good yields. This reaction was also applied to the synthesis of a polyether having allenyl side chains.

Methylplatinum triflate coordinated with 1,2-diphenyl-3,4-bis[(2,4,6-tri-t-butylphenyl)phosphinidene]cyclobutene serves as a highly selective catalyst for dehydrogenative silylation of ketones with HSiMe2Ph in the presence of pyridine as a co-catalyst, giving silyl enol ethers in high yields.

Lewis acid-catalyzed reaction of acetals with allenylsilanes and the three-component reactions of aldehydes, alkoxysilanes, and allenylsilanes are described. Both reactions are strongly dependent on the substituent at the α-position of allenylsilanes. Allenylsilanes having bulky substituents such as the tert-butyl and isopropyl groups result in the corresponding α-propargyl ethers in high yields, whereas allenylsilanes having the methyl and ethyl groups afford not only the corresponding α-propargyl ethers in low yield but also cyclopropyl ketones and α,β-unsaturated ketones as by-products.

The synthesis and utility of the novel axially chiral bis-urea ligand BINUREA are described. A complex of this urea ligand with ytterbium triflate and DBU can be used in the catalytic enantioselective Diels–Alder reaction of Danishefsky-type diene and electron-deficient olefins to give the adducts in good to excellent yield and enantiomeric excess (ee).

New 2-pyrone derivatives, dialkyl 3-cyano-6-phenyl-2-oxo-2H-pyran-4-ylmalonates and alkyl 3-cyano-6-phenyl-2-oxo-2H-pyran-4-ylacetates, which were easily prepared by the reaction of 6-aryl-4-methyl-sulfanyl-2-oxo-2H-pyran-3-carbonitriles with active methylene compounds in the presence of potassium carbonate, show fluorescence emission radiation. The light-emitting region of dimethyl 3-cyano-6-(4-N,N-dimethylamino)styryl-2-oxo-2H-pyran-4-ylmalonate (7h) was 620 nm in dichloromethane, making this compound a typical red fluorescent compound. Methyl 8-hydroxy-6-methyl-1-oxo-3-phenyl-1H-pyrano-[3,4-c]pyridine-5-carboxylate deriv-atives also showed fluorescence in the solid state. This is the first example of fluorescence in fused 2-pyrone derivatives.

2H-Pyrone derivatives were synthesized through the reaction of aryl acetyl compounds with ketene dithioacetals in the presence of sodium hydroxide, and they showed very strong fluorescence in the solid state. The light-emitting region of these 2H-pyrones is 447-630 nm in the solid states.

Bis-BINOLs 1a , b in which two BINOL units are tethered by o - and m -phenylenebis(ethynyl) groups form stable dinuclear bis-BINOLate titanium(IV) complexes 2a , b by treatment with titanium tetraisopropoxide. In the presence of excess titanium tetraisopropoxide, 2a and 2b (2–20 mol %) catalyze diethylzinc addition to aromatic and aliphatic aldehydes in an efficient manner to give the ethylation products with high enantioselectivities. While more than 1 equiv of titanium tetraisopropoxide (with respect to a substrate aldehyde) is generally employed for obtaining high turnover frequency and selectivity in reactions catalyzed by a parent (BINOLate)Ti(O i Pr) 2 , the amount can be reduced as low as 0.2 equiv in the reactions catalyzed by 2a , b .

For simultaneous construction of the polyurethane backbone and the allyl side chains, Lewis acid-catalyzed three-component condensation reactions of carbonyl compounds, N -trimethylsilylcarbamates, and allyltrimethylsilane are studied. The reaction of these three compounds took place in the presence of a catalytic amount of TrClO 4 at 0°C to yield the corresponding N -homoallylcarbamates in good yields. This reaction was also applied to the synthesis of a polyurethane having the allyl side chains.