BIOSYNTHESIS, PROPERTIES, AND CHEMISTRY OF CHLOROPHYLLS AND THEIR ROLE IN PHOTOSYNTHESIS IN PLANTS

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
201	2499	2000	100%

Progress 10/01/99 to 09/30/04

Outputs
In the current review period we have continued our productive studies on the synthesis and spectroscopic properties of sterically encumbered porphyrins, so as to establish the relationship between model spectroscopic signatures and excited states in photosynthesis. Thus, we have investigated the conformational and electronic effects of fluorine (electron-withdrawing) substituents on the photophysical properties of nonplanar porphyrins (Retsek et al., 2001). As a progression of our program to use natural plant chlorophyll derivatives as intermediates in the synthesis of anti-cancer agents, we have made several advances in the current review period. For example, we have synthesized novel vicinal diols and geminiketones which appear to be useful for photodynamic treatment of tumors (Chen et al., 2001). We have also investigated (using our synthetic porphyrins) the role of the benzodiazepine receptor in photodynamic therapy (Kessel et al., 2001), and have extended our new nitroporphyrin chemistry (described last year) to investigate directive effects of nitration during substitution of the porphyrin core (Wickramasinghe et al. 2001). Finally, in the area of our research associated with development of synthetic methodology, we have reported our first results on the synthesis of porphyrins bearing large fused aromatic components which enforce planarity in the corresponding part of the porphyrin core (Aihara et al., 2001).

Impacts
Basic sciences have had a tremendous impact on applied areas of agriculture. Our work involves chlorophyll chromophores, photosynthesis, formation of plant phytochromes, and disappearance of chlorophylls during senescence of leaves and fruit ripening. The work has contributed to basic chemical understanding of highly complex plant chromophores and systems.

Publications

Retsek, J. L.; Medforth, D. J.; Nurco, DS. J.; Gentemann, S.; Chirvony, V. S.; Smith, K. M.; Holten, D. (2001) Conformational and Electronic Effects of Phenyl-Ring Fluorination on the Photophysical Properties of Nonplanar Dodecaarylporphyrins. J. Phys. Chem., B 105, 6396-6411.
Chen, Y.; Medforth, C. J.; Smith, K. M.; Alderfer, J.; Dougherty, T. J.; Pandey, R. K. (2001) Effect of meso-Substituents on the Osmium Tetroxide Reaction and the Pinacol-Pinacolone Rearrangement in the Corresponding vic-Dihydroxyporphyrins. J. Org. Chem. 66, 3930-3939.
Kessel, D.; Antolovich, M.; Smith, K. M. (2001) The Role of the Peripheral Benzodiazepine Receptor in the Apoptotic Response to Photodynamic Therapy. Photochem. Photobiol. 74, 346-350.
Wickramasinghe, A.; Jaquinod, L.; Nurco, D. J.; Smith, K. M. (2001) Investigations on the Directive Effects of a Single meso-Substituent via Nitration of 5,12,13,17,18-Pentasubstituted Porphyrins: Syntheses of beta-Coplanar Nitroporphyrins. Tetrahedron 57, 4261-4269.
Aihara, H.; Jaquinod, L.; Nurco, D. J.; Smith, K. M. (2001) Multicarbocycle Formation Mediated by Arenoporphyrin 1,4-Diradicals: Synthesis of Picenoporphyrins. Angew. Chem. Int. Ed. 40, 3439-3441.

Progress 01/01/00 to 12/31/00

Outputs
We have continued our studies on the synthesis and spectroscopic properties of sterically encumbered porphyrins in connection with the relationship between model spectroscopic signatures and excited states in photosynthesis. Thus, we have demonstrated chirality in a sterically encumbered porphyrin system (Muzzi et al., 2000), and have also investigated the picosecond photochemical relaxation dynamics of singlet excited states in dodecaphenylporphyrin derivatives (Retsek et al., 2000). As a continuing part of our program to, use chlorophyll derivatives as intermediates in the synthesis of anti-cancer agents, we have also prepared amide-linked dimers and investigated the effect of various common substituents on their effect as photodynamic agents and on their photophysics (Zheng et al., 2000). A method for conversion of porphyrins into chlorophyll-type macrocycles, via nitroporphyrins (Shea et al. 2000), and basic procedures for synthesis of the nitroporphyrin starting materials (Siri et al., 2000) have also been described in recent publications. In the area of our research associated with development of synthetic methodology, we have reported our first results on the synthesis of porphyrins using solid-phase techniques (similar to the solid-phase techniques often used in peptide synthesis) (Montierth et al., 2000). Finally, a major review of synthetic approaches to porphyrins, and on the chemistry that can be used for their functionalization to give chemically and biologically useful derivatives, has been published (Vicente and Smith, 2000).

Impacts
Basic sciences have had a tremendous impact on applied areas of agriculture. Our work involves chlorophyll chromophores, photosynthesis, formation of plant phytochromes, and disappearance of chlorophylls during senescence of leaves and fruit ripening. The work has contributed to basic chemical understanding of highly complex plant chromophores and systems.

Publications

Muzzi, C. M.; Medforth, C. J.; Smith, K. M.; Jia, S. -L.; Shelnutt, J. A. (2000) Synthesis and Characterization of a Chiral Nonplanar Porphyrin. Chem. Commun. 131-132.
Siri, O.; Jaquinod, L.; Smit.h, K. M. (2000). Coplanar Conjugated beta-Nitroporphyrins and Some Aspects of Nitration of Porphyrins with N2O4. Tetrahedron Lett. 41, 3583-3586.
Shea, K. M.; Jaquinod, L.; Khoury, R. G.; Smith, K. M. (2000). Functionalization of 2,3-Disubstituted-2,3-dihydro-5,10,15,20-tetraphenylporphyrins. Tetrahedron 56:3139.
Retsek, J. L.; Gentemann, S.; Medforth, C. J.; Smith, K. M.; Chirvony, V. S.; Fajer, J.; Holten, D. (2000). Photoinduced Evolution on the Conformational Landscape of Nonplanar Dodecaphenylporphyrin: Picosecond Relaxation Dynamics in the Singlet (pi-pi(star)) Excited State. Phys. Chem. Lett, B 104, 6690-6693.
Vicente, M. G. H.; Smith, K. M. (2000) Porphyrins and Derivatives: Synthetic and Reactivity Profiles. Current Org. Chem. 4, 139-174.
Zheng, G.; Aoudia, M.; Lee, D.; Rodgers, M. A.; Smith, K. M.; Dougherty, T. J.; Pandey, R. K. (2000) Chlorin-Based Symmetrical and Unsymmetrical Dimers with Amide Linkages: Effect of the Substituents on Photodynamic and Photophysical Properties. J. Chem. Soc., Perkin Trans. 1 3113-3121.
Montierth, J. M.; Duran, A. G.; Leung, S. H.; Smith, K. M.; Schore, N. E. (2000) The Polymer-Supported MacDonald-Type Porphyrin Synthesis: Coupling of Two Dissimilar Dipyrromethanes. Tetrahedron Lett. 41, 7423-7426.

Progress 01/01/99 to 12/31/99

Outputs
During the biological conversion of hemes to give open-chain tetrapyrroles such as phytochrome (the growth and development regulator in plants), and other phycobilins, our earlier work had shown that so-called oxophlorins (5-oxoporphyrins) are involved in the first oxidative step. We have continued to investigate the fundamental chemistry of these oxophlorins and have shown that their primary mode of reactivity is through radical species (Khoury et al. 1999). Indeed, oxophlorins react very similarly to phenolic species, of which there are many examples in plants, and easily dimerize and even tetramerize. In the step after oxophlorin formation in plants (and in animals) it is believed that carbon monoxide is lost from the oxophlorin, and that an oxoniaporphyrin is produced (bearing an oxygen atom in the porphyrin ring at position-5. We have studied the chemistry of a zinc(II) oxoniaporphyrin (the zinc being regarded as a mimic of magnesium) and have shown that it undergoes nucleophilic addition at the 15-position (opposite the oxonia oxygen atom) (Clement et al., 1999). Much of our chemistry, including that involving oxophlorin radicals, has been published in a prestigious invited review (Vicente et al., 1999). For a number of years, in collaboration with Fajer's photosynthesis group in Argonne National Laboratory, we have been investigating the synthesis, chemistry, and photochemical signatures of certain nickel(II) porphyrins - use of nickel(II) in place of the magnesium(II) found in chlorophyll species allows a more stable compound to be handled, and also enables us to investigate the effect of a metal which has a very rich redox chemistry. Our current porphyrin chromophore was synthesized following our recently developed methods (Nelson et al., 1999; Jaquinod et al. 1999). We then showed that stereochemistry (particularly non-planarity) has a very significant effect on the photochemical signature, and that such porphyrins can be increasingly used as biomimetic models of conformational effects in photosynthetic chromophores and prosthetic groups in vivo.

Impacts
Basic sciences have had a tremendous impact on applied areas of agriculture. Our work involves chlorophyll chromophores, photosynthesis, formation of plant phytochromes, and disappearance of chlorophylls during senescence of leaves and fruit ripening. The work has contributed to basic chemical understanding of highly complex plant chromophores and systems.

Publications

Barkigia, K. M.; Nelson, N. Y.; Renner, M. W.; Smith, K. M.; Fajer, J. (1999). Structural Consequences of Spin Conversion in a Sterically Encumbered Ni(II) Porphyrin. J. Phys. Chem. B. 103, 8643-8646.
Clement, T. E.; Gerlach, B.; Senge, M. O.; Smith, K. M. (1999). Reactivity of Zinc(II) 5-Oxonia-Protoporphyrin-IX: Synthesis of the First 5-Oxonia-15-phlorin. Heterocycles 50, 641-644.
Jaquinod, L.; Khoury, R. G.; Shea, K. M.; Smith, K. M.. (1999). Regioselective Syntheses and Structural Characterizations of 2,3-Dibromo- and 2,3,7,8,12,13-Hexabromo-5,10,15,20-tetraphenylporphyrins. Tetrahedron 55, 13151-13158.
Khoury, R.G.; Jaquinod, L.; Paolesse, R.; Smith, K. M.. (1999). New Chemistry of Oxophlorins (Oxyporphyrins) and Their ?-Radicals. Tetrahedron 55, 6713-6732.
Nelson, N. Y.; Medforth, C. J.; Nurco, D. J.; Jia, S. -L.; Shelnutt, J. A.; Smith, K. M.. (1999). Synthesis and Unusual Properties of the First 2,3,7,8,12,13,17,18-Octabromo-5,10,15,20-tetraalkylporphyrin. Chem. Commun. 2071-2702.
Vicente, M. G. H.; Jaquinod, L.; Smith, K. M. (1999). Oligomeric Porphyrin Arrays. Chem. Commun. 1771-1782.

Progress 01/01/98 to 12/01/98

Outputs
3,8-Divinyl pigments (IUPAC nomenclature) have been proposed to be intermediates in the biosynthesis of chlorophylls and bacteriochlorophylls, and have recently been discovered in a variety of crops and plants; we have reported new chemical protection/deprotection methodology which has resulted in no less than three new synthetic approaches to 3,8-divinylpheophorbide-a (Gerlach et al., 1998). Of particular interest from the photosynthetic point of view is the observation that the change from ethyl to vinyl at the 8-position has no affect upon the electronic absorption spectrum, and thus upon the light absorption/harvesting properties of the final chlorophyll chromophores. The conversion of porphyrins into chlorins (dihydroporphyrins) is not easy to accomplish synthetically; we have now reported a completely new approach which involves reactions of "active methylene" compounds with nitroporphyrins (Shea et al., 1998a)., We have published several syntheses which utilize natural chlorophyll-a as the biological starting material; for example, we have prepared new benzochlorophylls which have quite remarkable red shifted optical spectra which make them excellent candidates as drugs in the photodynamic therapy modality for cancer treatment (Mettath et al., 1998). We have also investigated the syntheses and structure of a number of cofacially fixed tetrapyrrole chromophores as models for photosynthetic reaction center special pairs (Clement et al., 1998), and (with an eye on photosynthesis) have investigated the effect of distortions from planarity of chlorins upon the absorption.

Impacts
(N/A)

Publications

CLEMENT, T. E.; NURCO, D. J.; SMITH, K. M. (1998). Synthesis and Characterization of a Series of Monometallo-, Bimetallo-, and Heterobimetallo-1,2-ethene Linked Cofacial Bisporphyrins. Inorg. Chem. 37, 1150-1160.
GERLACH, B.; BRANTLEY, S. E.; SMITH, K. M. (1998). Novel Synthetic Routes to 8-Vinyl Chlorophyll Derivatives. J. Org. Chem. 63,
KRATTINGER, B.; NURCO, D. J.; SMITH, K. M. (1998). Novel Synthesis and New Chemistry of Naphthochlorins. Chem. Commun. 757-758.
METTATH, S.; SHIBATA, M.; ALDERFER, J. L.; SENGE, M. O.; SMITH, K. M.; REIN, R.; DOUGHERTY, T. J.; PANDEY, R. K. (1998). Synthesis and Spectroscopic Properties of Novel Benzochlorins Derived from Chlorophyll-a. J. Org. Chem. 63, 1646-1656.
SHEA, K. M.; JAQUINOD, L.; SMITH, K. M. (1998a). Dihydroporphyrin Synthesis: New Methodology. J. Org. Chem. 63, 7013-7021.
SHEA, K. M.; JAQUINOD, L.; KHOURY, R. G.; SMITH, K. M. (1998b). Dodecasubstituted Chlorins (Dihydroporphyrins). Chem. Commun.

Progress 01/01/97 to 12/01/97

Outputs
We have extended our work on the synthesis of methyl 3,8-divinyl-pheophorbide-a (IUPAC nomenclature) by developing completely new methods for protection of the 3-vinyl group in chlorophyll-a (Chl) derivatives (Brantley et al., 1997); the synthetic targets, so-called divinylchlorophylls, have recently been discovered in a variety of crops and plants. Using natural Chl as the sole biological starting material, we have completed several syntheses, and have obtained, tested, and investigated the photophysics of some potent sensitizers which can be used in tumor therapy (Zheng et al., 1997; Kozyrev et al., 1997); we have also investigated the in vivo photoactivity of dimers and trimers derived from Chl. Our studies on photosynthesis in plants and bacteria have also continued uninterrupted, and we have studied the photo-excited states of electronically perturbed chromophores (Gentemann et al., 1997) as well as self-assembled supramolecular antenna complexes containing Chl derivatives (Barkigia et al., 1997). Two structural studies of Chl derivatives have also appeared in the current review period (Senge and Smith, 1997a,b). Finally, we have continued the Chl bis-pheophorbides studies started last year, and have now accomplished the syntheses of novel poly-chromophore systems which interact electronically: examples include meso-meso linked dimers (Khoury et al., 1997), dimers bearing keto-ester side-chains similar to those found in Chl (Holmes et al., 1997) and a remarkable octameric porphyrin supramolecular array resembling a photosynthetic light-harvesting complex.

Impacts
(N/A)

Publications

BRANTLEY, S. E.; GERLACH, B.; OLMSTEAD, M. M.; SMITH, K. M. Vinyl Group Protection in Porphyrins and Chlorins: Organoselenium Derivatives. (1997). Tetrahedron Lett. 38, 937.
ZHENG, G.; PANDEY, R. K.; FORSYTH, T. P.; KOZYREV, A. N.; DOUGHERTY, T. J.; SMITH, K. M. (1997). Syntheses and Spectroscopic Studies of Some Novel Porphyrin-Pyropheophorbide Dimers and Trimers with Fixed Distances. Tetrahedron Lett.
KOZYREV, A. N.; ZHENG, G.; LAZAROU, E., DOUGHERTY, T. J.; SMITH, K. M.; PANDEY, R. K. (1997). Syntheses of Emeraldin and Purpurin-18 Analogs as Target-Specific Photosensitizers for Photodynamic Therapy.
GENTEMANN, NELSON, N. Y.; JAQUINOD, L.; NURCO, D. J.; LEUNG, S. H.; MEDFORTH, C. J.; SMITH, K. M.; FAJER, J.; HOLTEN. D. (1997). Variations and Temperature Dependence of the Excited State Properties of Conformationally and Electronically.
BARKIGIA, K. M.; MELAMED, D.; SWEET, R. M.; SMITH, K. M.; FAJER, J. (1997). Self-assembled Zinc Pheoporphyrin Dimers. Models for the Supramolecular Antenna Complexes of Green Photosynthetic Bacteria.
SENGE, M. O.; SMITH, K. M. (1997a). Bis(anhydromesorhodochlorinato XV methyl ester)zinc(II). Acta Crystallogr. C 53, 1022.
SENGE, M. O.; SMITH, K. M. (1997b). Structure and Conformation of Photosynthetic Pigments and Related Compounds. 10. Comparison of a Phytochlorin and Phytoporphyrin Derived from Chlorophyll a. Acta

Progress 01/01/96 to 12/30/96

Outputs
A preliminary communication describing the synthesis of methyl 3,8-divinyl-pheophorbide-a (IUPAC nomenclature) and a carbon-13 labeled derivative has now been published (Gerlach and Smith, 1996); the synthetic targets, so-called divinylchlorophylls, have recently been discovered in a variety of plants. Using chlorophyll-a (Chl) from algae and plants as the sole synthetic starting material, we have completed several organic partial syntheses, and have obtained, tested, and investigated the photophysics of some potent sensitizers (based on preliminary in-vivo tests) which can be used in tumor therapy (Pandey et al., 1996a-d). We have also synthesized some nucleoside adducts of Chl derivatives which may be useful in treatment of HIV (Jiang et al., 1996). We have been productive in the photosynthesis area, where we reported on spectroscopic signatures of pheophorbides (Renner et al., 1996), and on the syntheses of novel bis-porphyrin systems related to Chl (Paolesse et al., 1996). Finally, we have employed new low-valent titanium self-condensation methodology to prepared a number of dimeric species related to Chl (Jaquinod et al., 1996a), as well as some very novel planar, fully conjugated bis-pheophorbides from Chl which have red shifted optical spectra resembling those in the photosynthetic reaction center in plants and bacteria (Jaquinod et al., 1996b).

Impacts
(N/A)

Publications

GERLACH, B; SMITH, K. M. (1996). A Convenient Synthetic Approach to 8-Vinyl-chlorophyll Derivatives. Tetrahedron Lett. 37, 5431.
PANDEY, R. K.; JAGEROVIC, N.; RYAN, J. M.; DOUGHERTY, T. J.; SMITH, K. M. (1996a). Syntheses and Preliminary in vivo Photodynamic Efficacy of Benzoporphyrin Derivatives from Phyllo-erythrin and Rhodoporphyrin XV Methyl Esters and Aspartyl.
PANDEY, R. K.; CONSTANTINE, S.; GOFF, D. A.; KOZYREV, A. N.; DOUGHERTY, T. J.; SMITH, K. M. (1996b). Chlorophyll-a Derivatives in Photodynamic Therapy: Effect of Position of Heptyl Ether Side-Chains on in vivo Photosensitizing Activity.
JIANG, X.; PANDEY, R. K.; SMITH, K. M. (1996). Nucleoside Adducts of Vinylporphyrins and Vinylchlorins. J. Chem. Soc., Perkin Trans. 1. 1607.
PANDEY, R. K.; ZHENG, G.; LEE, D. A.; DOUGHERTY, T. J.; SMITH, K. M. (1996c). Comparative in vivo Sensitizing Efficacy of Porphyrin and Chlorin Dimers Joined with Ester, Ether, Carbon-Carbon, or Amide Bonds. J. Mol. Recogn. 9, 118.
PANDEY, R. K.; SUMLIN, A. B.; CONSTANTINE, S.; AOUDIA, M.; POTTER, W. R.; BELLNIER, D. A.; HENDERSON, B. W.; RODGERS, M. A.; SMITH, K. M.; DOUGHERTY, T. J. (1996d). Alkyl Ether Analogs of Chlorophyll-a Derivatives: Part 1. Synthesis,Photo.
RENNER, M. W.; ZHANG, Y.; NOY, D.; SCHERZ, A.; SMITH, K. M.; FAJER, J. (1996). Alternate Reaction Center Acceptors: Spectral Signatures and Redox Properties o.

Progress 01/01/95 to 12/30/95

Outputs
A post-doctoral in my group (Dr. Gerlach) has completed a synthesis of methyl 3,8-divinyl-pheophorbide-a (IUPAC nomenclature), a divinylchlorophyll-a derivative which has been shown to be widely distributed in certain cereals and plants; this work will be published. Our collaboration with Dr. Lagarias is also proceeding, and a new graduate student is working on organic syntheses of photochemically "locked" phytochrome models which Dr. Lagarias will then reconstitute into phytochrome apoproteins. Using chlorophyll-a (Chl) from algae and plants as a synthetic starting material, we have performed a number of complex organic syntheses, and have synthesized several highly potent (using in-vivo tests) sensitizers (benzochlorins) which can be used in tumor therapy (Kessel et al., 1995; Pandey et al., 1995), as well as including nucleoside adducts which may be useful in treatment of HIV infections (Jiang et al., 1995). Our projects involving photosynthesis have enjoyed a very productive year; for example, we have investigated (Senge et al., 1995a,b) structures of photosynthetic pigments (e.g. iron Chls and copper rhodochlorins), and have discovered a highly ruffled porphyrin (tetra-t-butylporphyrin) which has highly unusual excited state lifetimes which might provide an insight into phenomena which take place in photosynthetic systems (Senge et al., 1995c).

Impacts
(N/A)

Publications

Progress 01/01/94 to 12/30/94

Outputs
The following report describes progress in the three months since the project began on October 1, 1994. There is much interest in the structural differences between chlorins and their poryphyrin analogues, and this is related to the evolutionary choice of a chlorin (chlorophyll) rather than a porphyrin in photosynthesis. Using x-ray analysis of chlorophyll degradation products (chlorins and porphyrins) series, it was shown (Senge, et al., 1995) that chlorins have a very flexible core which can adopt different conformations. Work on the phytochrome and chlorophyll degradation (in senescent leaves) projects has been published: firstly, Pandey, et al. (1994) showed biliverdins bearing an "inverted" pyrrole subunit can be prepared. The chromophore exists in both a helical and hemi-extended form. Secondly, Isaac, et al., (1995) report the first example of ring opening of a chlorin macrocycle which exactly mimics the natural chlorophyll catabolic process in senescent leaves. All previous purely chemical procedures for ring opening of chlorins result in "unnatural" ring cleavage at the position next to the dihydro-ring. The new results describe a procedure for mimicking natural chlorophyll ring opening (at the 5-position), with unique structural assignment of the ring-opened product by x-ray crystallographic analysis.

Impacts
(N/A)

Publications