36151-61-8

Upstream product

• 186581-53-3 diazomethane 
• 56145-41-6 mesopyropheophorbide-a 
• 6453-67-4 methyl pyropheophorbide a 
• 7664-93-9 sulfuric acid 
• 5594-30-9 methylpheophorbide a 
• 15664-29-6 pheophorbide-a 
• 603-17-8 pheophytin a 
• 59954-18-6 methyl bacteriopheophorbide-d 
• 7647-01-0 hydrogenchloride 
• 10209-51-5 3-devinyl-3-acetyl-13⁽²⁾-demethoxycarbonylpheophorbide a methyl ester 
• 51742-45-1 methyl 20-bromo-meso(pyro)pheophorbide-a 
• 58326-67-3 pyropheophorbide-d methyl ester 
• 25145-41-9 pyrophaeophorbide b methyl ester 

Relevant academic research and scientific papers

Synthesis, optical properties and protonation of chlorophyll derivatives appending a pyridyl group in the C3-substituent

Chlorophyll(Chl)-a derivatives possessing a 2-(2/3/4-pyridyl)ethenyl group at the C3 position were synthesized by Wittig reaction of the 3-formyl group in methyl pyropheophorbide-d. The catalytic hydrogenation of the resulting 3-CC double bond afforded the corresponding regioisomers of Chls bearing the 3-(2-pyridylethyl) group. Comparing their visible absorption spectra in dichloromethane, the longest wavelength (Qy) maxima were shifted bathochromically in the following order: C-C a diluted solution gave an intense fluorescence emission band at the red-side region of Qy band and their fluorescence quantum yields were about 20%. The synthetic Chl-pyridine conjugates were titrated with trifluoroacetic acid in chloroform. Their visible spectral changes indicated that the appended pyridyl group was first protonated, followed by protonation of the chlorin π-system at the inner nitrogen atoms in a molecule.

Synthesis of 20-substituted chlorophyll derivatives with F-ring and optical properties of their less distorted chlorin π-systems

Under acidic conditions, methyl bacteriopheophorbides-d bearing a variety of substituents at the 20-position were dehydrated in a 1-hydroxyethyl group at the 3-position to give methyl 20-substituted pyropheophorbides-a. In the same pot, the resulting 3-vinyl group was successively cyclized at the 5-position to afford the corresponding 3,5-ethano-chlorins as analogs of sedimentary porphyrins with two exo-five-membered rings. The 20-substitution is essential to the cyclization to produce the additionally fused F-ring. After the ring closure, the 20-bromine atom and acetyl group were removed by the action of the same acid to give the 20-unsubstituted product. The steric size of the 20-substituents affected the cyclization as well as the electronic absorption and emission of the 3,5-ethano-chlorins in a solution. The F-ring fusion suppressed the conformational distortion of the chlorin π-plane, partially regulating the optical properties: decrease of red shifts in Qy maxima by the 20-substitution and reduction of almost all Stokes shifts.

Physicochemical and biochemical properties of synthetic zinc 131-(un)substituted chlorophyll-a derivatives

Zinc methyl pheophorbides a/a’, which possess oxo and methoxycarbonyl groups at the C131- and C132-positions, respectively, on the exo-five membered ring fusing the cyclic tetrapyrrole of their chlorin π-skeletons, were prepared via chemical modifications of chlorophyll a produced in phototrophs. The C131-hydroxylated and unsubstituted analogues were synthesized by reduction of the ketone moiety. The C131- and C132-stereochemistry of these semi-synthetic compounds was confirmed by 1H NMR and circular dichroism spectroscopies. A methoxycarbonyl group at the chiral C132-position in the ketone was stereo-inverted under basic conditions, whereas those in the corresponding alcoholic and dihydro-forms were not. The in vitro BciC enzymatic reaction of the (132R)-ketone was found to stereoselectively hydrolyze the C132-methoxycarbonyl group, followed by spontaneous decarboxylation. Similarly, the (132R)-COOCH3 group in the (131S)-alcohol was hydrolyzed, whereas the (132R)-COOCH3 group in the (131R)-alcohol was not. After the enzymatic reaction of the C131-dihydro-compound, its (132S)-demethoxycarbonylated and hydroxylated product was observed.

Site-selective C20-fluorinations of chlorophyll-a derivatives using N-fluorobenzenesulfonimide and their optical properties

Site-selective fluorinations at the C20 position of methyl pyropheophorbides-a, which is derived from naturally occurring chlorophyll(Chl)-a, were achieved by using N-fluorobenzenesulfonimide (NFSI). All the synthetic Chl-a derivatives possessing a variety of the C3-substituents (vinyl, ethyl, formyl, acetyl, hydroxymethyl, and 1-hydroxyethyl groups) were mono-fluorinated to produce the corresponding 20-fluoro-chlorins as isolated products. These fluorinated products were characterized by 1D/2D NMR, visible absorption, and fluorescence emission spectroscopy. Owing to the strong electronegativity of the C20-fluorine atom, their red-most Qy absorption and fluorescence emission bands were bathochromically shifted except for the C3-acetyl substitutes. This study showed not only tolerance of the chlorin π-skeleton and C3-substituents to NFSI but also potential availability of the fluorinated Chl library.

20-(N-Methylpyridiniumyl)ethynylated chlorophyll-a derivative with an intense Qx absorption band at a green to orange region

Methyl 20-substituted mesopyropheophorbides-a were prepared by the chemical modification of natural chlorophyll-a via palladium-catalyzed cross-coupling reactions. The 20-ethynylation and further 2-pyridylation showed bathochromic shifts in their visible absorption bands as well as hyperchromic effects of the Qx bands in a diluted chloroform solution. The protonation and methylation at the nitrogen atom of the 202-pyridyl group induced much larger shifts and effects, especially giving red-shifted and intensified Qx bands.

Synthesis of monovinyl- and divinyl-chlorophyll analogs and their physical properties

Chlorophyll-a was chemically modified to methyl pyropheophorbides-a possessing 3,8-diethyl, 3-vinyl-8-ethyl, 3-ethyl-8-vinyl, and 3,8-divinyl groups. Analogous 3-ethyl-7-vinyl- and 3,7-divinyl-chlorins were prepared by derivatization of chlorophyll-b. The synthetic free bases as well as zinc 3-vinyl-chlorins were dissolved in THF and the monomeric diluted solutions were characterized by optical spectroscopy including visible absorption, circular dichroism, and fluorescence emission spectra. The optical data indicated that the 3-vinylation bathochromically shifted the visible (Soret/Qx/Qy) absorption and fluorescence emission maxima, the 7-vinylation moved the Soret/Qx and Qy/emission bands to longer and slightly shorter wavelengths, respectively, and the 8-vinylation induced red shifts of the Soret/Qx maxima and no (or faint red) shifts of the Qy/emission maxima. Zinc complexes of 3,7- and 3,8-divinyl-chlorins showed almost the same optical properties including fluorescence emission quantum yields and lifetimes as well as the same first oxidation potentials, thus, 3,7-divinyl-chlorophyll-a could be considered an alternative pigment to the naturally occurring 3,8-divinyl analog.

Coordination-Driven Dimerization of Zinc Chlorophyll Derivatives Possessing a Dialkylamino Group

Zinc chlorophyll derivatives Zn-1–3 possessing a tertiary amino group at the C31 position have been synthesized through reductive amination of methyl pyropheophorbide-d obtained from naturally occurring chlorophyll-a. In a dilute CH2Cl2 solution as well as in a dilute 10 %(v/v) CH2Cl2/hexane solution, Zn-1 possessing a dimethylamino group at the C31 position showed red-shifted UV/Vis absorption and intensified exciton-coupling circular dichroism (CD) spectra at room temperature owing to its dimer formation via coordination to the central zinc by the 31-N atom of the dimethylamino group. However, Zn-2/3 bearing 31-ethylmethylamino/diethylamino groups did not. The difference was dependent on the steric factor of the substituents in the tertiary amino group, where an increase of the carbon numbers on the N atom reduced the intermolecular N???Zn coordination. UV/Vis, CD, and 1H NMR spectroscopic analyses including DOSY measurements revealed that Zn-1 formed closed-type dimers via an opened dimer by single-to-double axial coordination with an increase in concentration and a temperature decrease in CH2Cl2, while Zn-2/3 gave open and flexible dimers in a concentrated CH2Cl2 solution at low temperature. The supramolecular closed dimer structures of Zn-1 were estimated by molecular modelling calculations, which showed these structures were promising models for the chlorophyll dimer in a photosynthetic reaction center.

Synthesis of chlorophyll-a derivatives methylated in the 3-vinyl group and their intrinsic site energy

Wittig reaction of methyl pyropheophorbide-d possessing the 3-formyl group gave readily methyl pyropheophorbides-a bearing a variety of 3-alkenyl groups as semi-synthetic models of chlorophyll-a. The 3-substituents rotated around the C3-C31 bond from the coplanar conformation with the chlorin π-system, moving the redmost visible absorption maxima to a shorter wavelength. The model experiments showed that natural chlorophyll-a carrying the 3-vinyl group would take a similar rotamer to control its intrinsic site energy.

Self-Aggregation of synthetic zinc chlorophyll derivatives possessing 31-hydroxy or methoxy group and 131-mono-or dicyanomethylene moiety in nonpolar organic solvents as models of chlorosomal bacteriochlorophyll-d aggregates

Methyl 131-(di)cyanomethylene-pyropheophorbides were synthesized by Knoevenagel reactions of the corresponding 131-oxo-chlorins prepared from modifying chlorophyll-A with malononitrile or cyanoacetic acid. Alternatively, methyl 131-cyanomethylene-pyropheophorbides were produced by Wittig reactions of 131-oxo-chlorins with Ph3P=CHCN. Selfaggregation of zinc complexes of the semi-synthetic chlorophyll derivatives possessing a hydroxy or methoxy group at the 31-position was examined in 1%(v/v) tetrahydrofuran or dichloromethane and hexane by electronic absorption and circular dichroism spectroscopy. Although intermolecular hydrogen-bonding between the 31-hydroxy and 131-oxo groups of bacteriochlorophylls-c/d/e/f was essential for their self-Aggregation in natural light-harvesting antenna systems (=chlorosomes), zinc 31-hydroxy-131-di/monocyanomethylenechlorins self-Aggregated in the less/lesser polar organic solvents to form chlorosome-like large oligomers in spite of lacking the 131-oxo moiety as the hydrogen-bonding acceptor. Zinc 31-methoxy-131-dicyanomethylene-chlorin gave similar self-Aggregates regardless of lack of both the 31-hydroxy and 131-oxo groups. The present self-Aggregation was ascribable to stronger coordination of the 31-oxygen atom to the central zinc than the conventional systems, where the electron-withdrawing cyano group(s) increased the coordinative ability of the central zinc through the chlorin p-system.

Self-aggregation of a synthetic zinc chlorophyll derivative possessing a 131-dicyanomethylene group as a light-harvesting antenna model

Zinc methyl 3-hydroxymethyl-131-dicyanomethylene- pyropheophorbide-a, one of the bacteriochlorophyll-d analogs, was prepared by modifying chlorophyll-a. The semi-synthetic compound self-aggregated in an aqueous Triton X-100 solution to give large oligomers with red-shifted and broadened electronic absorption bands. The J-aggregates were similar to self-aggregates of bacteriochlorophyll-d molecules in natural light-harvesting antennas of green photosynthetic bacteria. The strongly electron-withdrawing dicyanomethylene group was an alternative functional moiety of the hydrogen-bond accepting 131-oxo group which had been necessary for such self-aggregation.