36151-60-7

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 
• 7647-01-0 hydrogenchloride 
• 6453-67-4 3¹,3²-didehydrophytochlorin 
• 67-56-1 methanol 
• 39391-40-7 chlorophyll α 
• 25145-41-9 pyrophaeophorbide b methyl ester 
• 58326-67-3 pyropheophorbide-d methyl ester 

Relevant academic research and scientific papers

Synthesis of 20-iodochlorophyll derivatives and their properties including reactivity, electronic absorption, and self-aggregation

Methyl 20-iodopyropheophorbides-a possessing several substituents at the 3-position were prepared by treatment of the corresponding 20-unsubstituted chlorophyll-a derivatives with iodine and [bis(trifluoroacetoxy)iodo]benzene in chloroform and water at room temperature. The sterically demanding 20-iodination was clean, efficient, and regioselective without alteration of the 3-substituents, and also highly reproducible. The resulting 20-iodides were so reactive that they were readily transformed into 20-acetylchlorin (Pd-catalyzed cross-coupling) and 20-unsubstituted chlorin (acidic deiodination). Electronic absorption spectra in dichloromethane showed that the 20-iodination shifted the maxima to longer wavelengths in their monomeric states. Zinc complexes of 31-hydroxy-20-iodo-131-oxochlorins self-aggregated in non-polar organic solvents to give red-shifted and broadened absorption bands, similarly as in the corresponding 20-unsubstituted molecules, which are good models of the main light-harvesting antenna systems in photosynthetic green bacteria.

Synthesis of 3,20-disubstituted chlorophyll-a derivatives and reactivity of the substituents

Methyl 20-bromo-pyropheophorbide-a possessing a vinyl group at the 3-position and its analogs having 3-ethyl, 3-(1-hydroxyethyl) and 3-acetyl groups were prepared by modifying naturally occurring chlorophyll(Chl)-a. The 20-bromo-chlorins were cross-coupled with vinyl- and 1-ethoxyvinyl-tributyltins in the presence of a Pd(0) catalyst to afford 20-vinyl- and acetyl-chlorins, respectively. The interconversions among the above four C2-functional groups at the 3-position were readily performed in the semi-synthetic Chl derivatives, but no modification of the 20-vinyl and acetyl groups was observed. The difference of the chemical reactivity is ascribable to the steric factor: the 3 1-position was less sterically hindered than the 20 1-position. Single hydrogenation and hydration of 3,20-divinyl-chlorin and reduction of 3,20-diacetylchlorin proceeded exclusively at the 3-position. The redmost (Qy) bands in electronic absorption spectra of the semi-synthetic Chl derivatives in a diluted dichloromethane solution were controlled by the 3,20-substituents. The 3-substituent effect on their Qy maxima was determined by the electronic factor (their electronegativity), while the 20-substituent effect was primarily dependent on the steric factor (their local size).

Modification of 3-substituents in (bacterio)chlorophyll derivatives to prepare 3-ethylated, methylated, and unsubstituted (nickel) pyropheophorbides and their optical properties

Methyl mesopyropheophorbide-a possessing an ethyl group at the 3-position, its 31-demethyl analogue (3-methyl homologue), and its 3 1-deethyl analogue (3-unsubstituted chlorin) were prepared by modifying naturally occurring (bacterio)chlorophylls bearing 3-vinyl, formyl, acetyl, and 1-hydroxyethyl groups. These synthetic 3-(un)substituted chlorophyll derivatives and their nickel complexes are probable intermediates during degradation of (bacterio)chlorophylls to chemically stable porphyrinoids. The optical properties (visible absorption, circular dichroism, and fluorescence emission) of the catabolic candidates in a solution were measured, and the substitution effect was investigated.

Synthesis and optical properties of C3-ethynylated chlorin and π-extended chlorophyll dyads

A C3-ethynylated chlorophyll derivative was prepared from methyl pyropheophorbide-d possessing a 3-formyl group by treatment of Bestmann-Ohira reagent. The mono-substituted acetylene was subjected to coupling reactions at the terminal acetylenic carbon at

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.

Hemisynthesis of 132,173-cyclomesopheophorbide-a-enol

Cyclopheophorbides are often major chlorophyll-a degradation products in biogeochemical situations. Authentic standards are unavailable and facile generation of pure compounds is required. 132,173- Cyclomesopheophorbide-a-enol (mesoCYCLO) was prepared in moderate yields via a known Dieckmann-like condensation of mesopyropheophorbide-a methyl ester (mpPBIDaME). MesoCYCLO was purified by flash chromatography over a polymeric reversed phase (PRP-1) material, negating the requirement for a crystallization step. Structural verification included ultraviolet-visible spectrometry, high resolution matrix (sulfur/CS2) assisted laser desorption mass spectrometry, and nuclear magnetic resonance.

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.

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.

Syntheses and optical properties of stable 8-alkylidene-bacteriochlorins mimicking the molecular structures of natural bacteriochlorophylls-b and g

We prepared bacteriochlorophyll(BChl)-b and g models by Diels-Alder reactions of 8-vinyl-chlorophylls with tetracyanoethylene. The resulting 8-alkylidene-bacteriochlorins with various substituent groups at the 3-position had the same π-conjugate as BChls-b/g. While the natural pigments isomerized by addition of an acid to afford the corresponding chlorins, the synthetic models were stable under the acidic conditions due to dialkylation at the 7-position. These BChl-b/g models are useful for investigating the optical properties of relatively unstable BChls-b/g. Chemically stable 8-alkylidene-bacteriochlorins were systematically prepared as models of natural bacteriochlorophylls-b/g easily isomerizing to the corresponding chlorins, and their optical properties were investigated in detail.

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.