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11.
Let G be a graph and f : V(G)→{1,3,5,…}. Then a subgraph H of G is called a (1,f)-odd subgraph if degH(x){1,3,…,f(x)} for all xV(H). If f(x)=1 for all xV(G), then a (1,f)-odd subgraph is nothing but a matching. A (1,f)-odd subgraph H of G is said to be maximum if G has no (1,f)-odd subgraph K such that |K|>|H|. We show that (1,f)-odd subgraphs have some properties similar to those of matchings, in particular, we give a formula for the order of a maximum (1,f)-odd subgraph, which is similar to that for the order of a maximum matching. 相似文献
12.
Tetsuji Kametani Hideo Lida Shinzo Kano Sadao Tanaka Keiichiro Fukumoto Shiroshi Shibuya Haruhiko Yagi 《Journal of heterocyclic chemistry》1967,4(1):85-92
Schotten-Baumann reaction of the amine (X) with 4-benzyloxy-3,4′-oxydiphenylacetyl chloride (XI) gave two amides, (XIIa) and (XIIb), which were cyclized to give the corresponding 3,4-dihydroisoquinolines, respectively. Methylation of the above 3,4-dihydro-isoquinolines, followed by hydrolysis, afforded the compounds having the same composition as berbamine (Ia) and oxyacanthine (Ib), whose structures are under examination. 相似文献
13.
Molecular and electronic structural properties of the hydrogen-bonded complexes of p-quinone dianions (PQ(2)(-)) were investigated by electrochemistry and spectroelectrochemistry of PQ in MeCN combined with ab initio MO calculations. Hydrogen bonding between PQ(2)(-) and MeOH was measured as the continuous positive shift of the apparent second half-wave reduction potentials with increasing concentrations of MeOH. Detailed analyses of the behavior reveal that PQ(2)(-) forms the 1:2 hydrogen-bonded complexes at low concentrations of MeOH and the 1:4 complexes at high concentrations, yielding the formation constants. Temperature dependence of the formation constants allows us to yield the formation energy as 76.6 and 118.9 kJ mol(-)(1) for the 1:2 and 1:4 complex formation of the 1,4-benzoquinone dianion (BQ(2)(-)) with MeOH, respectively. These results show that the pi-dianions involving the quinone carbonyl groups exhibit very strong hydrogen-accepting ability. The longest wavelength band of the spectra of BQ(2)(-) and the chloranil dianion (CL(2)(-)) is assigned to the (1)B(3u) <-- (1)A(g) band mainly contributed from an intramolecular charge-transfer (CT) configuration. Hydrogen bonding allows the band of BQ(2)(-) and CL(2)(-) to be blue-shifted, depending on the strength of the hydrogen bonds. CNDO/S-CI calculations reveal that the blue shift is ascribed to stabilization of the ground state by the hydrogen bonding involving strong n-sigma-type CT interaction. The HF/6-31G(d) calculation results show that the structure of PQ(2)(-) is characterized by a lengthening of the C=O bonds and a benzenoid ring. The geometrical properties of the hydrogen-bonded complexes of PQ(2)(-) are a slight lengthening of the C=O bonds and a short distance of the hydrogen bonds. It is demonstrated that this situation is due to the strong n-sigma CT interaction in the hydrogen bonds. The results suggest that the differing functions and properties of biological quinones are conferred by the n-sigma CT interaction through hydrogen bonding of the dianions with their protein environment. 相似文献
14.
Tsuyoshi Miura Satoshi Tsujino Kohtaro Goto Midori Noguchi Manabu Node Nobuyuki Imai 《Tetrahedron》2005,61(27):6518-6526
The use of the bisfluorous chain-type propanoyl (Bfp) group as a fluorous protective group made it possible to rapidly synthesize the Gb2 and Gb3 oligosaccharide derivatives by a simple fluorous-organic extraction purification. Furthermore, the fluorescence-labeled Gb2 and Gb3 oligosaccharides were prepared as a potential Vero Toxins detecting reagent. 相似文献
15.
Platelet aggregation potentiators from cho-rei 总被引:4,自引:0,他引:4
W Lu I Adachi K Kano A Yasuta K Toriizuka M Ueno I Horikoshi 《Chemical & pharmaceutical bulletin》1985,33(11):5083-5087
16.
Kiyotake Suenaga Tsuyoshi Mutou Takashi Itoh Noboru Takada Masaki Takagi Hideo Kigoshi Kiyoyuki Yamada 《Tetrahedron》2004,60(38):8509-8527
The bioassay-guided fractionation of the cytotoxic constituents of the Japanese sea hare Dollabella auricularia led to the isolation of aurilide (1), a 26-membered cyclodepsipeptide. The gross structure of 1 was established by spectroscopic analysis including 2D NMR techniques. The absolute stereostructure was determined by chiral HPLC analysis of acid hydrolysates of 1 and by the enantioselective synthesis of a degradation product arising from a dihydroxylated fatty acid portion. The enantioselective synthesis of 1 was achieved in 12% overall yield (16 steps) and confirmed the absolute stereostructure of 1. The cytotoxicity of 1 was evaluated using a synthetic sample, which was found to exhibit potent cytotoxicity against HeLa S3 cells with an IC50 of 0.011 μg/mL. Further biological and pharmacological studies of 1 have been carried out by using synthetic 1. 相似文献
17.
Tsuyoshi Otsuka 《Tetrahedron letters》2004,45(12):2643-2647
A novel and efficient oxidative dimerization of 1-naphthols 1 with dioxygen in the presence of several semiconductors including SnO2, ZrO2, and activated charcoal as catalytic mediators took place selectively to give the corresponding 2,2′-binaphthols 2 or 2,2′-binaphthyl-1,1′-quinones 3 in excellent yields without light irradiation. Among these semiconductors, the catalytic activity of SnO2 could be fully restored by appropriate reactivation treatment after oxidation. The products 2 and 3 should be useful as synthetic intermediates for natural binaphthyls. 相似文献
18.
The reaction of the dianion of phenylsulfinylacetone with alkyl halides afforded beta-keto sulfoxides, which were first chlorinated with hexachloroethane and then treated successively with KH and t-BuLi to give carboxylic acids in three-steps in moderate overall yields from the alkyl halides. This procedure affords a good method for a synthesis of carboxylic acids from alkyl halides with three-carbon elongation. 相似文献
19.
A linearized optimal control method in combination with mixed quantum/classical molecular dynamics simulation is used for numerically investigating the possibility of controlling photodissociation wave packets of I(2)(-) in water. Optimal pulses are designed using an ensemble of photodissociation samples, aiming at the creation of localized dissociation wave packets. Numerical results clearly show the effectiveness of the control although the control achievement is reduced with an increase in the internuclear distance associated with a target region. We introduce effective optimal pulses that are designed using a statistically averaged effective dissociation potential, and show that they semiquantitatively reproduce the control achievements calculated by using optimal pulses. The control mechanisms are interpreted from the time- and frequency-resolved spectra of the effective optimal pulses. 相似文献
20.
A series of 1-amino-5-substituted uracils and their 4-thio or 2,4-dithio substituted analogues were synthesized and assayed for anti-conflict activity in rats and anesthetic activity in mice. 1-Amino-5-halogenouracils 3b-e, 1-amino-4-thiouracil (9a), and 1-amino-5-halogeno-4-thiouracils 9c, d showed both anti-conflict and anesthetic activities. The most active compound was 1-amino-5-chloro-4-thiouracil (9d) which showed anxiolytic activity at 2 mg/kg of oral administration (p.o.) on a modified Geller-Seifter conflict schedule. Its minimum effective dose (MED) was lower than that of diazepam. The 50 percent effective dose (ED50) for anesthetic activity in mice of the compound (9d) was 32.9 mg/kg, p.o. 相似文献