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Hitoshi Tamiaki - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis of chlorophyll-f analogs possessing the 2-Formyl Group by modifying chlorophyll-a.
    Bioorganic & Medicinal Chemistry Letters, 2014
    Co-Authors: Yusuke Kinoshita, Hitoshi Tamiaki
    Abstract:

    A methyl Group at the 2-position of methyl mesopyropheophorbide-a was transformed to the 2-Formyl Group to give methyl mesopyropheophorbide-f, one of the chlorophyll-f analogs. The 2-Formylation moved the redmost electronic absorption band in a solution to a longer wavelength and the bathochromic shift was comparable to that by the 3-Formylation. Zinc complex of the synthetic compound in solutions showed similar visible absorption spectra as those of naturally occurring chlorophyll-f.

  • Demetalation kinetics of the zinc chlorophyll derivative possessing two Formyl Groups: effects of Formyl Groups conjugated to the chlorin macrocycle on physicochemical properties of photosynthetic pigments
    Journal of Porphyrins and Phthalocyanines, 2013
    Co-Authors: Kana Sadaoka, Hitoshi Tamiaki, Shigenori Kashimura, Toru Oba, Yoshitaka Saga
    Abstract:

    Demetalation kinetics of zinc chlorophyll derivative 1 possessing two Formyl Groups directly linked to the A- and B-rings of the chlorin macrocycle, which was synthesized from chlorophyll b, was examined under acidic conditions and compared with those of Zn chlorins 2 and 3 possessing a single Formyl Group in the A- and B-ring, respectively, as well as Zn chlorin 4 lacking any Formyl Group to unravel the substitution effects on demetalation properties of chlorophyllous pigments. Demetalation kinetics of diFormylated Zn chlorin 1 was slower than those of monoFormylated Zn chlorins 2 and 3, indicating that the effect of the electron-withdrawing Formyl Group on demetalation kinetics was amplified by introduction of two Formyl Groups to the chlorin macrocycle. High correlations were observed between demetalation rate constants of Zn chlorins 1–4 and the sum of Hammett σ parameters of the 3- and 7-substituents on the chlorin macrocycle, indicating that the combination of electron-withdrawing abilities of the substituents linked directly to the cyclic tetrapyrrole was responsible for demetalation properties of zinc chlorophyll derivatives.

  • Substitution effects in the A- and B-rings of the chlorin macrocycle on demetalation properties of zinc chlorophyll derivatives.
    Journal of Physical Chemistry B, 2011
    Co-Authors: Yuki Hirai, Hitoshi Tamiaki, Shigenori Kashimura, Shin-ichi Sasaki, Yoshitaka Saga
    Abstract:

    Effects of peripheral substituents in the A- and B-rings of the chlorin macrocycle on demetalation of zinc chlorophyll derivatives were examined. The demetalation rate constants of zinc 8-Formyl-chlorin (1) were comparable to those of zinc 3-Formyl-chlorin (2). Both 1 and 2 exhibited significantly slower demetalation kinetics than the corresponding zinc chlorin 3, which had no Formyl Group. Comparison of demetalation kinetics between zinc 3-ethyl-chlorin (3) and zinc 3-vinyl-chlorin (4) indicated that the substitution at the 3-position of the chlorin macrocycle from a vinyl to an ethyl Group accelerated removal of the central zinc. Activation energies of demetalation of zinc chlorins 1, 2, and 5 possessing a Formyl Group in the A- or B-ring of the chlorin macrocycle were larger than those of zinc chlorins 3 and 4 lacking a Formyl Group. These results indicate that the Formyl Groups in the A- or B-ring provide tolerance to demetalation of chlorin molecules due to their electron-withdrawing effects.

  • Demetalation kinetics of natural chlorophylls purified from oxygenic photosynthetic organisms: effect of the Formyl Groups conjugated directly to the chlorin π-macrocycle
    Photochemical and Photobiological Sciences, 2009
    Co-Authors: Yuki Hirai, Hitoshi Tamiaki, Shigenori Kashimura, Yoshitaka Saga
    Abstract:

    Demetalation kinetics of natural chlorophyll (Chl) d purified from Acaryochloris marina was first studied and compared with those of Chls a and b. The demetalation rate constant of Chl d, which possessed a Formyl Group at the 3-position, was five-fold smaller than that of Chl a possessing a vinyl Group at the same position in aqueous acetone at the proton concentration of 1.2 × 10−3 M at 25 °C. In contrast, the demetalation rate constant of Chl b possessing a Formyl Group at the 7-position was 26 times smaller than that of Chl a. The activation energy of demetalation reaction of Chl d was larger than that of Chl a, but smaller than that of Chl b. These indicate that the substitution effect of 3-Formyl Group on the acidic removal of central magnesium in Chls was smaller than that of 7-Formyl Group.

  • Study on C8‐substituent effects of synthetic bacteriochlorophyll‐d/f analogues
    AIP Conference Proceedings, 2004
    Co-Authors: Shin-ichi Sasaki, Hitoshi Tamiaki
    Abstract:

    Bacteriochlorophyll(=BChl)s‐ c/d/e are known to be major pigments constructing the main light‐harvesting antennae of photosynthetic green bacteria. In this study, methyl bacteriopheophorbide‐d derivatives having a series of alkyl or alkenyl substituents at the 8‐position and their zinc complexes were synthesized, and their visible absorption spectra and self‐aggregation in a solution were examined. It was shown that the C8‐substituents conjugating with the chlorin π‐system cause red‐shifts of the Qx peaks in their monomeric forms, but do not strongly affect the supramolecular structure of the self‐aggregates along the Qy axis. Furthermore, 31‐epimerically pure Zn‐MBPhe‐f analogues possessing the C8‐Formyl Group were also synthesized, and their spectral characteristics were compared to those of the C7‐Formyl compounds. It was found that the C8‐Formyl Group cause drastic spectral changes both in monomeric and oligomeric forms compared to the spectra of Zn‐MBPhe‐f having the C7‐Formyl Group. For example, sel...

Alfredo Toscano - One of the best experts on this subject based on the ideXlab platform.

  • new stibines containing acetal and Formyl Group platinum complex and unexpected oxastibol derivative
    Journal of Organometallic Chemistry, 2006
    Co-Authors: Pankaj Sharma, Diego Perez, Noe Rosas, Armando Cabrera, Alfredo Toscano
    Abstract:

    Abstract A new tertiary stibine ligand (1) containing acetal Group at the ortho-position has been synthesized. This new stibine was then complexed with PtCl 4 2 - to obtain trans-PtCl2L2 (2) where stibine acts as a monodentate ligand. The acetal was hydrolyzed in a slightly acidic medium and forms a very new stibine (3) containing Formyl Group at the ortho-position. When (3) was reduced with NaBH4 an unusual oxastibol (4) derivative was obtained under the experimental conditions used. All the compounds were characterized by IR, mass, 1H, 13C, COSY and HETCOR NMR spectroscopy. The molecular structures of (2), (3) and (4) were determined. Compound (3) crystallizes in two different polymorphs (3a) and (3b) and both the polymorphs show hypervalent antimony with three Sb⋯O interactions and the molecule exists in O-cis-exo configuration. Compound (4) shows intramolecular Sb⋯O interactions. To the best of our knowledge this is the first report on organoantimony compounds containing carbonyl Groups though their phosphorus and bismuth analogues are well known. Compound (2) shows helicoidal chirality, which is a very new concept in antimony chemistry

  • New stibines containing acetal and Formyl Group: Platinum complex and unexpected oxastibol derivative
    Journal of Organometallic Chemistry, 2006
    Co-Authors: Pankaj Sharma, Diego Perez, Noe Rosas, Armando Cabrera, Alfredo Toscano
    Abstract:

    Abstract A new tertiary stibine ligand (1) containing acetal Group at the ortho-position has been synthesized. This new stibine was then complexed with PtCl 4 2 - to obtain trans-PtCl2L2 (2) where stibine acts as a monodentate ligand. The acetal was hydrolyzed in a slightly acidic medium and forms a very new stibine (3) containing Formyl Group at the ortho-position. When (3) was reduced with NaBH4 an unusual oxastibol (4) derivative was obtained under the experimental conditions used. All the compounds were characterized by IR, mass, 1H, 13C, COSY and HETCOR NMR spectroscopy. The molecular structures of (2), (3) and (4) were determined. Compound (3) crystallizes in two different polymorphs (3a) and (3b) and both the polymorphs show hypervalent antimony with three Sb⋯O interactions and the molecule exists in O-cis-exo configuration. Compound (4) shows intramolecular Sb⋯O interactions. To the best of our knowledge this is the first report on organoantimony compounds containing carbonyl Groups though their phosphorus and bismuth analogues are well known. Compound (2) shows helicoidal chirality, which is a very new concept in antimony chemistry

Shin-ichi Sasaki - One of the best experts on this subject based on the ideXlab platform.

  • Substitution effects in the A- and B-rings of the chlorin macrocycle on demetalation properties of zinc chlorophyll derivatives.
    Journal of Physical Chemistry B, 2011
    Co-Authors: Yuki Hirai, Hitoshi Tamiaki, Shigenori Kashimura, Shin-ichi Sasaki, Yoshitaka Saga
    Abstract:

    Effects of peripheral substituents in the A- and B-rings of the chlorin macrocycle on demetalation of zinc chlorophyll derivatives were examined. The demetalation rate constants of zinc 8-Formyl-chlorin (1) were comparable to those of zinc 3-Formyl-chlorin (2). Both 1 and 2 exhibited significantly slower demetalation kinetics than the corresponding zinc chlorin 3, which had no Formyl Group. Comparison of demetalation kinetics between zinc 3-ethyl-chlorin (3) and zinc 3-vinyl-chlorin (4) indicated that the substitution at the 3-position of the chlorin macrocycle from a vinyl to an ethyl Group accelerated removal of the central zinc. Activation energies of demetalation of zinc chlorins 1, 2, and 5 possessing a Formyl Group in the A- or B-ring of the chlorin macrocycle were larger than those of zinc chlorins 3 and 4 lacking a Formyl Group. These results indicate that the Formyl Groups in the A- or B-ring provide tolerance to demetalation of chlorin molecules due to their electron-withdrawing effects.

  • Study on C8‐substituent effects of synthetic bacteriochlorophyll‐d/f analogues
    AIP Conference Proceedings, 2004
    Co-Authors: Shin-ichi Sasaki, Hitoshi Tamiaki
    Abstract:

    Bacteriochlorophyll(=BChl)s‐ c/d/e are known to be major pigments constructing the main light‐harvesting antennae of photosynthetic green bacteria. In this study, methyl bacteriopheophorbide‐d derivatives having a series of alkyl or alkenyl substituents at the 8‐position and their zinc complexes were synthesized, and their visible absorption spectra and self‐aggregation in a solution were examined. It was shown that the C8‐substituents conjugating with the chlorin π‐system cause red‐shifts of the Qx peaks in their monomeric forms, but do not strongly affect the supramolecular structure of the self‐aggregates along the Qy axis. Furthermore, 31‐epimerically pure Zn‐MBPhe‐f analogues possessing the C8‐Formyl Group were also synthesized, and their spectral characteristics were compared to those of the C7‐Formyl compounds. It was found that the C8‐Formyl Group cause drastic spectral changes both in monomeric and oligomeric forms compared to the spectra of Zn‐MBPhe‐f having the C7‐Formyl Group. For example, sel...

  • self assembly of synthetic bacteriochlorophyll f analogues having c8 Formyl Group
    Bulletin of the Chemical Society of Japan, 2004
    Co-Authors: Shin-ichi Sasaki, Hitoshi Tamiaki
    Abstract:

    31-Epimerically pure C8-Formyl analogues Zn–3R/S of zinc methyl bacteriopheophorbide-f (Zn–MBPhe-f) were synthesized. Their spectroscopic and self-aggregation properties were compared to those of Z...

Yoshitaka Saga - One of the best experts on this subject based on the ideXlab platform.

  • Effects of the central metal on stretching vibrational bands of the peripheral carbonyl moieties in Formylated chlorophyll derivatives studied by Fourier-transform infrared spectroscopy
    Journal of Porphyrins and Phthalocyanines, 2014
    Co-Authors: Kana Sadaoka, Yoshitaka Saga
    Abstract:

    The vibrational properties of metal complexes of monoFormylated and diFormylated chlorophyll derivatives were compared with those of the corresponding free-base chlorins to unravel the effects of the central metal on the carbonyl stretching vibration modes of the peripheral oxygen functional Groups in the chlorin macrocycle by means of FTIR spectroscopy. The 3- C = O stretching vibrational bands of a 3-Formyl Group were shifted to lower wavenumbers by insertion of Zn and Cu into the center of the 3-Formyl free-base chlorin. In contrast, the 7- and 8- C = O stretching vibrational bands of the Formyl Groups linked to the B-ring of the chlorin macrocycle were barely shifted even if 7- and 8-Formyl free-base chlorins were metalated. The down-shifts of the 3- C = O and few shifts of the 7-/8- C = O vibrational stretching bands were in line with the results of DFT calculations. The difference in the effects of the central metal on the vibrational properties between the Formyl Group in the A-ring and those in the B-ring is ascribable to the different conjugation manners with the adjacent π-system: the 3-Formyl Group was connected to the chlorin 18π-system, whereas the 7-/8-Formyl Groups were conjugated to the rather isolated C 7– C 8 double bond. The 13- C = O stretching vibrational bands were shifted to lower wavenumbers by metalation. These down-shifts can also be rationalized by invoking the conjugation of the 13-keto Group with the chlorin 18π-system.

  • Demetalation kinetics of the zinc chlorophyll derivative possessing two Formyl Groups: effects of Formyl Groups conjugated to the chlorin macrocycle on physicochemical properties of photosynthetic pigments
    Journal of Porphyrins and Phthalocyanines, 2013
    Co-Authors: Kana Sadaoka, Hitoshi Tamiaki, Shigenori Kashimura, Toru Oba, Yoshitaka Saga
    Abstract:

    Demetalation kinetics of zinc chlorophyll derivative 1 possessing two Formyl Groups directly linked to the A- and B-rings of the chlorin macrocycle, which was synthesized from chlorophyll b, was examined under acidic conditions and compared with those of Zn chlorins 2 and 3 possessing a single Formyl Group in the A- and B-ring, respectively, as well as Zn chlorin 4 lacking any Formyl Group to unravel the substitution effects on demetalation properties of chlorophyllous pigments. Demetalation kinetics of diFormylated Zn chlorin 1 was slower than those of monoFormylated Zn chlorins 2 and 3, indicating that the effect of the electron-withdrawing Formyl Group on demetalation kinetics was amplified by introduction of two Formyl Groups to the chlorin macrocycle. High correlations were observed between demetalation rate constants of Zn chlorins 1–4 and the sum of Hammett σ parameters of the 3- and 7-substituents on the chlorin macrocycle, indicating that the combination of electron-withdrawing abilities of the substituents linked directly to the cyclic tetrapyrrole was responsible for demetalation properties of zinc chlorophyll derivatives.

  • Substitution effects in the A- and B-rings of the chlorin macrocycle on demetalation properties of zinc chlorophyll derivatives.
    Journal of Physical Chemistry B, 2011
    Co-Authors: Yuki Hirai, Hitoshi Tamiaki, Shigenori Kashimura, Shin-ichi Sasaki, Yoshitaka Saga
    Abstract:

    Effects of peripheral substituents in the A- and B-rings of the chlorin macrocycle on demetalation of zinc chlorophyll derivatives were examined. The demetalation rate constants of zinc 8-Formyl-chlorin (1) were comparable to those of zinc 3-Formyl-chlorin (2). Both 1 and 2 exhibited significantly slower demetalation kinetics than the corresponding zinc chlorin 3, which had no Formyl Group. Comparison of demetalation kinetics between zinc 3-ethyl-chlorin (3) and zinc 3-vinyl-chlorin (4) indicated that the substitution at the 3-position of the chlorin macrocycle from a vinyl to an ethyl Group accelerated removal of the central zinc. Activation energies of demetalation of zinc chlorins 1, 2, and 5 possessing a Formyl Group in the A- or B-ring of the chlorin macrocycle were larger than those of zinc chlorins 3 and 4 lacking a Formyl Group. These results indicate that the Formyl Groups in the A- or B-ring provide tolerance to demetalation of chlorin molecules due to their electron-withdrawing effects.

  • Demetalation kinetics of natural chlorophylls purified from oxygenic photosynthetic organisms: effect of the Formyl Groups conjugated directly to the chlorin π-macrocycle
    Photochemical and Photobiological Sciences, 2009
    Co-Authors: Yuki Hirai, Hitoshi Tamiaki, Shigenori Kashimura, Yoshitaka Saga
    Abstract:

    Demetalation kinetics of natural chlorophyll (Chl) d purified from Acaryochloris marina was first studied and compared with those of Chls a and b. The demetalation rate constant of Chl d, which possessed a Formyl Group at the 3-position, was five-fold smaller than that of Chl a possessing a vinyl Group at the same position in aqueous acetone at the proton concentration of 1.2 × 10−3 M at 25 °C. In contrast, the demetalation rate constant of Chl b possessing a Formyl Group at the 7-position was 26 times smaller than that of Chl a. The activation energy of demetalation reaction of Chl d was larger than that of Chl a, but smaller than that of Chl b. These indicate that the substitution effect of 3-Formyl Group on the acidic removal of central magnesium in Chls was smaller than that of 7-Formyl Group.

  • Synthesis of homologously pure bacteriochlorophyll-e and f analogues from BChls-c/d via transformation of the 7-methyl to Formyl Group and self-aggregation of synthetic zinc methyl bacteriopheophorbides-c/d/e/f in non-polar organic solvent
    Tetrahedron, 2003
    Co-Authors: Hitoshi Tamiaki, Miki Omoda, Yoshitaka Saga, Hidetada Morishita
    Abstract:

    Abstract Homologously pure methyl bacteriopheophorbides-e and f (BPhes-e/fM) were prepared from modification of naturally occurring bacteriochlorophylls-c and d (BChls-c/d), respectively, by transformation of the methyl to Formyl Group at the 7-position. The absolute configuration of the 1-hydroxyethyl Group at the 3-position of (Zn-)BPhes-e/fM was determined from comparison with structurally known BChl-c/d epimers. Visible spectra of synthetic (Zn-)BPhe-c/d/e/fM showed that the 71-oxidation and the 82/121/20-methylation affected Soret, Qx and Qy bands of both the monomeric (in a polar organic solvent) and oligomeric species (in a non-polar solvent).

Pankaj Sharma - One of the best experts on this subject based on the ideXlab platform.

  • new stibines containing acetal and Formyl Group platinum complex and unexpected oxastibol derivative
    Journal of Organometallic Chemistry, 2006
    Co-Authors: Pankaj Sharma, Diego Perez, Noe Rosas, Armando Cabrera, Alfredo Toscano
    Abstract:

    Abstract A new tertiary stibine ligand (1) containing acetal Group at the ortho-position has been synthesized. This new stibine was then complexed with PtCl 4 2 - to obtain trans-PtCl2L2 (2) where stibine acts as a monodentate ligand. The acetal was hydrolyzed in a slightly acidic medium and forms a very new stibine (3) containing Formyl Group at the ortho-position. When (3) was reduced with NaBH4 an unusual oxastibol (4) derivative was obtained under the experimental conditions used. All the compounds were characterized by IR, mass, 1H, 13C, COSY and HETCOR NMR spectroscopy. The molecular structures of (2), (3) and (4) were determined. Compound (3) crystallizes in two different polymorphs (3a) and (3b) and both the polymorphs show hypervalent antimony with three Sb⋯O interactions and the molecule exists in O-cis-exo configuration. Compound (4) shows intramolecular Sb⋯O interactions. To the best of our knowledge this is the first report on organoantimony compounds containing carbonyl Groups though their phosphorus and bismuth analogues are well known. Compound (2) shows helicoidal chirality, which is a very new concept in antimony chemistry

  • New stibines containing acetal and Formyl Group: Platinum complex and unexpected oxastibol derivative
    Journal of Organometallic Chemistry, 2006
    Co-Authors: Pankaj Sharma, Diego Perez, Noe Rosas, Armando Cabrera, Alfredo Toscano
    Abstract:

    Abstract A new tertiary stibine ligand (1) containing acetal Group at the ortho-position has been synthesized. This new stibine was then complexed with PtCl 4 2 - to obtain trans-PtCl2L2 (2) where stibine acts as a monodentate ligand. The acetal was hydrolyzed in a slightly acidic medium and forms a very new stibine (3) containing Formyl Group at the ortho-position. When (3) was reduced with NaBH4 an unusual oxastibol (4) derivative was obtained under the experimental conditions used. All the compounds were characterized by IR, mass, 1H, 13C, COSY and HETCOR NMR spectroscopy. The molecular structures of (2), (3) and (4) were determined. Compound (3) crystallizes in two different polymorphs (3a) and (3b) and both the polymorphs show hypervalent antimony with three Sb⋯O interactions and the molecule exists in O-cis-exo configuration. Compound (4) shows intramolecular Sb⋯O interactions. To the best of our knowledge this is the first report on organoantimony compounds containing carbonyl Groups though their phosphorus and bismuth analogues are well known. Compound (2) shows helicoidal chirality, which is a very new concept in antimony chemistry