Microwave spectroscopy of the ν8-ν6 band of diacetylene

Vibration-rotation transitions of diacetylene between the first excited states of the ν₆ (CCH symmetric bending) and the ν₈ (CCH antisymmetric bending) vibrations were observed with a Stark modulation microwave spectrometer. The rotational, centrifugal distortion and l-type doubling constants of the two vibrational states were determined as follows with 2.5 σ uncertainties in parentheses.

     

252.

Identification of the peptide epimerase MslH responsible for d-amino acid introduction at the C-terminus of ribosomal peptides     

Zhi Feng  Yasushi Ogasawara  Tohru Dairi 《Chemical science》2021,12(7):2567

A lasso peptide MS-271 is a ribosomally synthesized and post-translationally modified peptide (RiPP) consisting of 21 amino acids with a d-tryptophan (Trp) at its C terminus. The presence of d-amino acids is rare in RiPPs and few mechanisms of d-amino acid introduction have been characterized. Here, we report the identification of MslH, previously annotated as a hypothetical protein, as a novel epimerase involved in the post-translational epimerization of the C-terminal Trp residue of the precursor peptide MslA. MslH is the first epimerase that catalyzes epimerization at the C_α center adjacent to a carboxylic acid in a cofactor-independent manner. We also demonstrate that MslH exhibits broad substrate specificity toward the N-terminal region of the core peptide, showing that MslH-type epimerases offer opportunities in peptide bioengineering.

The biosynthesis of d-tryptophan containing lasso peptide MS-271 involves the epimerization of a ribosomal peptide MslA catalyzed by a novel class of metal- and cofactor-independent peptide epimerase MslH.     

253.

Cloud point temperature of polyoxyethylene-type nonionic surfactants and their mixtures   总被引：1，自引：0，他引：1  

Inoue T  Ohmura H  Murata D 《Journal of colloid and interface science》2003,258(2):374-382

The cloud point temperature, T(c), was investigated for aqueous solutions of poly(oxyethylene) alkyl ethers, C(n)E(m), and their mixtures. The experimental T(c)'s for single surfactant systems were analyzed according to the Flory-Huggins model for cloud point phenomenon, and the enthalpy and the entropy changes associated with the process of the separation of micellar solution into pure water and pure surfactant were estimated. It was found that the enthalpy-entropy compensation relationship holds for this process. The Flory-Huggins model was extended to the binary surfactant mixtures, and the expression of T(c) as a function of the composition was derived assuming the regular solution for mixed micelles. The experimental results of T(c) obtained for mixtures of C(n)E(m) were well reproduced by the model calculation. Discussion is given concerning the interaction parameters of different surfactant species in mixed micelles determined by this model calculation.     

254.

The size-selective synthesis of folded oligomers by dynamic templation     

Nishinaga T  Tanatani A  Oh K  Moore JS 《Journal of the American Chemical Society》2002,124(21):5934-5935

A dynamic pool of m-phenylene ethynylene oligomers generated by sequence ligation using the imine metathesis reaction was equilibrated under a variety of conditions, and the mixture of products was analyzed by HPLC. The equilibration was performed in the presence and absence of rodlike ligand 2b, which exhibits an affinity for the helical oligomers that is very length specific. Among the eight oligomers generated during metathesis equilibrium, the formation of 22-mer 6b was enhanced in acetonitrile in the presence of 2b. This particular oligomer has the highest binding affinity for 2b. Quantitative analysis by HPLC of the products indicated that 6b was produced in 66% yield in the presence of 2 equiv 2b while a 37% yield was produced in the absence of 2b. Judging from the binding affinities of oligomers 6 with 2b, the equilibrium shifting was driven by the selective binding of 6b with 2b.     

255.

Trapping adsorption of carbon monoxide located between carbon dioxide adsorbed on magnesium oxide     

Masayoshi Kobayashi  Tohru Kanno 《Reaction Kinetics and Catalysis Letters》1987,34(2):329-332

Carbon monoxide adsorbed on MgO is strongly trapped by the adsorbed carbon dioxide, increasing the heat of adsorption from 85.4 to 184.1 kJ/mol. The trapped CO is thought to be captured by two or three adsorbed CO₂ and becomes less active to react with oxygen.

---

, MgO, , 85,4 184,1 /. , CO CO₂ .

     

256.

Synthetic studies on (+)-naphthyridinomycin: stereoselective synthesis of the tetracyclic core framework     

Mori K  Rikimaru K  Kan T  Fukuyama T 《Organic letters》2004,6(18):3095-3097

[reaction: see text] The stereoselective synthesis of the tetracyclic intermediate 21 for (+)-naphthyridinomycin (1) has been accomplished. The convergent synthesis used the Ugi 4CC reaction with the amine derivative 10. The key features of the stereoselective synthesis of 21 were the intramolecular Mizoroki-Heck reaction, an aromatic-aldehyde cyclization, and a stereoselective hydroboration.     

257.

Bioluminescence imaging of the response of rat gliosarcoma to ALA-PpIX-mediated photodynamic therapy     

Moriyama EH  Bisland SK  Lilge L  Wilson BC 《Photochemistry and photobiology》2004,80(2):242-249

Photodynamic therapy (PDT) is a promising modality for the treatment of solid tumors that combines a photosensitizing agent and light to produce cytotoxic reactive oxygen species that lead to tumor cell death. The recent introduction of bioluminescence imaging (BLI), involving the use of the luciferase gene (luc) transferred into target tumor cells, followed by systemic administration of luciferin and detection of the emitted visible chemiluminescence photons, offers the potential for longitudinal imaging of tumor growth and therapeutic response in single animals. We demonstrate in this study the first results of the use of BLI to assess the response of an intracranial brain tumor model (9L rat gliosarcoma) to aminolevulinic acid (ALA)-mediated PDT. Complementary in vitro experiments with the luciferase-transfected 9L cells show that the decrease in the luminescent signal after PDT correlates with cell kill. In vivo imaging shows a decrease in the BLI signal from the tumor after ALA-PDT treatment, followed by tumor regrowth. Furthermore, preliminary studies using cells transfected with a hypoxia-responsive vector show an increase in bioluminescence within 4 h after Photofrin-mediated PDT, demonstrating the ability to observe stress-gene responses. These results suggest that BLI can be used to provide spatiotemporal information of intracranial brain tumor responses after PDT and may serve as a valuable response-endpoint measure.     

258.

Dehydro[12]- and -[18]annulenes fused with tetrafluorobenzene: synthesis,electronic properties,packing structures,and reactivity in the solid state     

Nishinaga T  Nodera N  Miyata Y  Komatsu K 《The Journal of organic chemistry》2002,67(17):6091-6096

Dehydro[12]- and -[18]annulenes 3 and 4 fused with tetrafluorobenzene were newly synthesized by the copper-mediated oxidative coupling of 1,2-diethynyltetrafluorobenzene. The UV-vis spectra of 3 and 4 showed the maximum absorption to be almost identical to that of the corresponding unsubstituted benzodehydro[12]- and -[18]annulenes 1 and 2, respectively, while the reduction waves in cyclic voltammetry observed at potentials of -1.48 and -1.56 V vs Fc/Fc(+) for 3 and 4 were less negative than those for 1 and 2. In agreement with these results, theoretical calculations (B3LYP/6-31G(d)) indicated that the HOMO-LUMO gap is similar for 1 and 3 and for 2 and 4 but that the LUMO levels of 3 and 4 are apparently lowered by the electronegative fluorine substituents. The X-ray crystallography of single crystals grown from 3 (crystal A), 3.C(6)H(6) (crystal B), and a mixture of 1 and 3 (crystal C) demonstrated that the molecules of 3 are stacked in a slanted manner in crystals A and B, while those of 1 and 3 form sandwichlike 1:2 complexes (3.1.3) that are stacked in a columnar arrangement in crystal C. Despite the suitable packing for topochemical polymerization, crystals A-C were quite stable against photochemical reaction. In contrast, differential scanning calorimetry showed that the thermal polymerization occurred explosively at 120-135 degrees C.     

259.

Syntheses of monomethoxy polyethyleneglycol vinyl ether macromonomers and their radical copolymerization with maleic anhydride     

Tohru Suzuki  Tsugikazu Tomono 《Journal of polymer science. Part A, Polymer chemistry》1984,22(11):2829-2839

In order to develop new biocompatible materials, monomethoxy polyethyleneglycol vinyl ethers (Me(EG)_n VE, n = 1–39) were synthesized from the corresponding monomethoxy polyethyleneglycol with acetylene. Successful purification of the macromonomers was performed by some adsorption procedures such as charcoal and ion-exchange resin treatments. The Me(EG)_n VE macromonomers were easily copolymerized with maleic anhydride (MAn) to give alternating copolymers. The copolymerization rates significantly depended on the ethyleneglycol chain length of the Me(EG)_n VE, resulting in relatively lower polymerization rate of higher MW macromonomer. The use of nonelectron donor solvent such as carbon tetrachloride led to higher yields and higher MW of copolymers.     

260.

Furopyridines. XXIV. Nitration,chlorination, acetoxylation and cyanation of 2,3-dihydrofuro[2,3-b]-, -[3,2-b]-, -[2,3-c]- and -[3,2-c]pyridine N-Oxides     

Shunsaku Shiotani  Masahide Kurosaki  Katsunori Taniguchi  Miwa Moriyama 《Journal of heterocyclic chemistry》1997,34(3):941-952

Nitration of 2,3-dihydrofuro[3,2-b]- N-oxide 3b and -[2,3-c]pyridine N-oxide 3c afforded the nitropyridine compounds 4b, 5b and 6 from 3b and 4c, 5c, 5′c and 7 from 3c , while -[2,3-b]- N-oxide 3a and -[3,2-c]pyridine N-oxide 3d did not give the nitro compound. Chlorination of 3b and 3c with phosphorus oxychloride yielded mainly the chloropyridine derivatives 15b, 15′b from 3b and 15c and 15′c from 3c , whereas 3a and 3d gave pyridine derivatives formed through fission of the 1–2 ether bond of the furo-pyridines 13a , 14 and 13d . Acetoxylation of 3b and 3c gave 3-acetoxy derivatives 18b and 18c and the parent compound 1b and 1c . Acetoxylation of 3a yielded compounds formed through fission of the 1–2 bond 16 and 17 and 3d gave furopyridones 19 and 19 ′. Cyanation of 3b and 3c yielded mainly the cyanopyridine compounds 20b, 20c and 20′c . Cyanation of 3a and 3d gave the cyanopyridine compounds 20a , 20d and 20′d accompanying formation of the pyridine derivatives 21a, 21d and 21′d .     

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	$\text{B}{}_{\mathrm{v}}\text{(}\text{MHz}\text{)}$	$\text{D}{}_{\mathrm{v}}\text{(}\text{kHz}\text{)}$	$\text{q}{}_{\mathrm{v}}\text{(}\text{MHz}\text{)}$
$\text{ν}{}_6$	4391.3230(84)	0.582(154)	2.4830(32)
$\text{ν}{}_8$	4391.1921(94)	0.594(179)	2.4073(37)

Identification of the peptide epimerase MslH responsible for d-amino acid introduction at the C-terminus of ribosomal peptides

A lasso peptide MS-271 is a ribosomally synthesized and post-translationally modified peptide (RiPP) consisting of 21 amino acids with a d-tryptophan (Trp) at its C terminus. The presence of d-amino acids is rare in RiPPs and few mechanisms of d-amino acid introduction have been characterized. Here, we report the identification of MslH, previously annotated as a hypothetical protein, as a novel epimerase involved in the post-translational epimerization of the C-terminal Trp residue of the precursor peptide MslA. MslH is the first epimerase that catalyzes epimerization at the C_α center adjacent to a carboxylic acid in a cofactor-independent manner. We also demonstrate that MslH exhibits broad substrate specificity toward the N-terminal region of the core peptide, showing that MslH-type epimerases offer opportunities in peptide bioengineering.

The biosynthesis of d-tryptophan containing lasso peptide MS-271 involves the epimerization of a ribosomal peptide MslA catalyzed by a novel class of metal- and cofactor-independent peptide epimerase MslH.     

Cloud point temperature of polyoxyethylene-type nonionic surfactants and their mixtures

The cloud point temperature, T(c), was investigated for aqueous solutions of poly(oxyethylene) alkyl ethers, C(n)E(m), and their mixtures. The experimental T(c)'s for single surfactant systems were analyzed according to the Flory-Huggins model for cloud point phenomenon, and the enthalpy and the entropy changes associated with the process of the separation of micellar solution into pure water and pure surfactant were estimated. It was found that the enthalpy-entropy compensation relationship holds for this process. The Flory-Huggins model was extended to the binary surfactant mixtures, and the expression of T(c) as a function of the composition was derived assuming the regular solution for mixed micelles. The experimental results of T(c) obtained for mixtures of C(n)E(m) were well reproduced by the model calculation. Discussion is given concerning the interaction parameters of different surfactant species in mixed micelles determined by this model calculation.     

The size-selective synthesis of folded oligomers by dynamic templation

A dynamic pool of m-phenylene ethynylene oligomers generated by sequence ligation using the imine metathesis reaction was equilibrated under a variety of conditions, and the mixture of products was analyzed by HPLC. The equilibration was performed in the presence and absence of rodlike ligand 2b, which exhibits an affinity for the helical oligomers that is very length specific. Among the eight oligomers generated during metathesis equilibrium, the formation of 22-mer 6b was enhanced in acetonitrile in the presence of 2b. This particular oligomer has the highest binding affinity for 2b. Quantitative analysis by HPLC of the products indicated that 6b was produced in 66% yield in the presence of 2 equiv 2b while a 37% yield was produced in the absence of 2b. Judging from the binding affinities of oligomers 6 with 2b, the equilibrium shifting was driven by the selective binding of 6b with 2b.     

Trapping adsorption of carbon monoxide located between carbon dioxide adsorbed on magnesium oxide

Carbon monoxide adsorbed on MgO is strongly trapped by the adsorbed carbon dioxide, increasing the heat of adsorption from 85.4 to 184.1 kJ/mol. The trapped CO is thought to be captured by two or three adsorbed CO₂ and becomes less active to react with oxygen.

---

, MgO, , 85,4 184,1 /. , CO CO₂ .

     

Synthetic studies on (+)-naphthyridinomycin: stereoselective synthesis of the tetracyclic core framework

[reaction: see text] The stereoselective synthesis of the tetracyclic intermediate 21 for (+)-naphthyridinomycin (1) has been accomplished. The convergent synthesis used the Ugi 4CC reaction with the amine derivative 10. The key features of the stereoselective synthesis of 21 were the intramolecular Mizoroki-Heck reaction, an aromatic-aldehyde cyclization, and a stereoselective hydroboration.     

Bioluminescence imaging of the response of rat gliosarcoma to ALA-PpIX-mediated photodynamic therapy

Photodynamic therapy (PDT) is a promising modality for the treatment of solid tumors that combines a photosensitizing agent and light to produce cytotoxic reactive oxygen species that lead to tumor cell death. The recent introduction of bioluminescence imaging (BLI), involving the use of the luciferase gene (luc) transferred into target tumor cells, followed by systemic administration of luciferin and detection of the emitted visible chemiluminescence photons, offers the potential for longitudinal imaging of tumor growth and therapeutic response in single animals. We demonstrate in this study the first results of the use of BLI to assess the response of an intracranial brain tumor model (9L rat gliosarcoma) to aminolevulinic acid (ALA)-mediated PDT. Complementary in vitro experiments with the luciferase-transfected 9L cells show that the decrease in the luminescent signal after PDT correlates with cell kill. In vivo imaging shows a decrease in the BLI signal from the tumor after ALA-PDT treatment, followed by tumor regrowth. Furthermore, preliminary studies using cells transfected with a hypoxia-responsive vector show an increase in bioluminescence within 4 h after Photofrin-mediated PDT, demonstrating the ability to observe stress-gene responses. These results suggest that BLI can be used to provide spatiotemporal information of intracranial brain tumor responses after PDT and may serve as a valuable response-endpoint measure.     

Dehydro[12]- and -[18]annulenes fused with tetrafluorobenzene: synthesis,electronic properties,packing structures,and reactivity in the solid state

Dehydro[12]- and -[18]annulenes 3 and 4 fused with tetrafluorobenzene were newly synthesized by the copper-mediated oxidative coupling of 1,2-diethynyltetrafluorobenzene. The UV-vis spectra of 3 and 4 showed the maximum absorption to be almost identical to that of the corresponding unsubstituted benzodehydro[12]- and -[18]annulenes 1 and 2, respectively, while the reduction waves in cyclic voltammetry observed at potentials of -1.48 and -1.56 V vs Fc/Fc(+) for 3 and 4 were less negative than those for 1 and 2. In agreement with these results, theoretical calculations (B3LYP/6-31G(d)) indicated that the HOMO-LUMO gap is similar for 1 and 3 and for 2 and 4 but that the LUMO levels of 3 and 4 are apparently lowered by the electronegative fluorine substituents. The X-ray crystallography of single crystals grown from 3 (crystal A), 3.C(6)H(6) (crystal B), and a mixture of 1 and 3 (crystal C) demonstrated that the molecules of 3 are stacked in a slanted manner in crystals A and B, while those of 1 and 3 form sandwichlike 1:2 complexes (3.1.3) that are stacked in a columnar arrangement in crystal C. Despite the suitable packing for topochemical polymerization, crystals A-C were quite stable against photochemical reaction. In contrast, differential scanning calorimetry showed that the thermal polymerization occurred explosively at 120-135 degrees C.     

Syntheses of monomethoxy polyethyleneglycol vinyl ether macromonomers and their radical copolymerization with maleic anhydride

In order to develop new biocompatible materials, monomethoxy polyethyleneglycol vinyl ethers (Me(EG)_n VE, n = 1–39) were synthesized from the corresponding monomethoxy polyethyleneglycol with acetylene. Successful purification of the macromonomers was performed by some adsorption procedures such as charcoal and ion-exchange resin treatments. The Me(EG)_n VE macromonomers were easily copolymerized with maleic anhydride (MAn) to give alternating copolymers. The copolymerization rates significantly depended on the ethyleneglycol chain length of the Me(EG)_n VE, resulting in relatively lower polymerization rate of higher MW macromonomer. The use of nonelectron donor solvent such as carbon tetrachloride led to higher yields and higher MW of copolymers.     

Furopyridines. XXIV. Nitration,chlorination, acetoxylation and cyanation of 2,3-dihydrofuro[2,3-b]-, -[3,2-b]-, -[2,3-c]- and -[3,2-c]pyridine N-Oxides

Nitration of 2,3-dihydrofuro[3,2-b]- N-oxide 3b and -[2,3-c]pyridine N-oxide 3c afforded the nitropyridine compounds 4b, 5b and 6 from 3b and 4c, 5c, 5′c and 7 from 3c , while -[2,3-b]- N-oxide 3a and -[3,2-c]pyridine N-oxide 3d did not give the nitro compound. Chlorination of 3b and 3c with phosphorus oxychloride yielded mainly the chloropyridine derivatives 15b, 15′b from 3b and 15c and 15′c from 3c , whereas 3a and 3d gave pyridine derivatives formed through fission of the 1–2 ether bond of the furo-pyridines 13a , 14 and 13d . Acetoxylation of 3b and 3c gave 3-acetoxy derivatives 18b and 18c and the parent compound 1b and 1c . Acetoxylation of 3a yielded compounds formed through fission of the 1–2 bond 16 and 17 and 3d gave furopyridones 19 and 19 ′. Cyanation of 3b and 3c yielded mainly the cyanopyridine compounds 20b, 20c and 20′c . Cyanation of 3a and 3d gave the cyanopyridine compounds 20a , 20d and 20′d accompanying formation of the pyridine derivatives 21a, 21d and 21′d .