Synthesis and Stereochemistry of Hydroporphyrins

Scheer, Hugo

doi:10.1016/b978-0-12-220102-8.50008-7

Cited by 14 publications

(5 citation statements)

References 187 publications

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“…Likewise, Y 189 and K 193 (equivalent to Y275 and K279 in Pea POR) are juxtaposed on the opposing face of the pchlide ring, ideally placed to donate a proton to C 18 in the second step of the reaction. Additions of H − and H + in this manner yield the correct stereochemistry26 of (17 S, 18 S) for the product chlide.…”

Section: Resultsmentioning

confidence: 92%

Protochlorophyllide oxidoreductase: A homology model examined by site‐directed mutagenesis

et al. 2001

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An homology model of protochlorophyllide reductase (POR) from Synechocystis sp. was constructed on a template from the tyrosine-dependent oxidoreductase family. The model showed characteristics appropriate to a globular, soluble protein and was used to generate a structure of the ternary complex of POR, nicotinamide adenine dinucleotide phosphate (NADPH), and protochlorophyllide. The POR ternary model was validated by mutagenesis experiments involving predicted coenzyme-binding residues and by chemical modification experiments. A core tryptophan residue was shown to be responsible for much of the protein's fluorescence. Both quenching of this residue by coenzyme and fluorescence resonance energy transfer (FRET) from the protein to the coenzyme allowed the binding constant of NADPH to be determined. Replacement of this residue by Tyr gave an active mutant with approximately halved fluorescence and a negligible FRET signal, consistent with the role of this residue in energy transfer to the NADPH at the active site and with the model. The mechanism of the enzyme is discussed in the context of the model and semiempirical molecular orbital calculations.

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Section: Resultsmentioning

confidence: 92%

Protochlorophyllide oxidoreductase: A homology model examined by site‐directed mutagenesis

et al. 2001

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“…The methodology for working with tetrapyrrole macrocycles has changed profoundly since Woodward’s iconic synthesis of chlorin e 6 trimethyl ester. Scheer’s pungent observation 78 in 1978 “in spite of the straightforward reactions now available to prepare the common model chlorins like [ H 2 OEC ] and [ H 2 TPC ], there is still no generally applicable set of conditions to obtain chlorins with sensitive substituents” can now surely be revised on the basis of the methodological advances described herein. Given the generational nature of methodology, perhaps the intellectual framework and advances described in this review will provide a foundation for the invention of powerful new routes in the future, where the magic wizardry of synthesis enables even more facile creation of chlorins and chlorin-containing architectures to obtain a deeper understanding of our green world.…”

Section: Discussionmentioning

confidence: 99%

“…Research on gem-dialkylchlorins represents the shortest of the five threads, originating around 1980, but synthetic advances for creating gem-dialkylchlorins already present great versatility. Numerous routes to chlorins have been developed, and these approaches have been reviewed over the years ,− yet none treats the gem-dialkylchlorins in significant depth. Methods wherein a porphyrin undergoes cycloaddition or rearrangement of preattached substituents to give a gem-dialkyl group are not treated here.…”

Section: Introductionmentioning

confidence: 99%

De NovoSynthesis of Gem-Dialkyl Chlorophyll Analogues for Probing and Emulating Our Green World

2015

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Woodward reported his infamous synthesis of chlorin e 6 trimethyl ester, a known synthetic precursor to chlorophyll a. [59][60][61][62][63][64]124 The work was posited on a half-century of intensive studies by many investigators in tetrapyrrole chemistry and began a decade after the close of Fischer's lifetime of research 125−128 (which included an uncompleted synthetic program directed toward chlorophylls 15 ). Indeed, "he read all the umpteen papers on the chlorophylls written by Willstaẗter and Fischer, including the experimental parts." 129 The Woodward synthesis of chlorin e 6 trimethyl ester required 46 steps, of which 24 were spent on converting the sole precursor, Knorr's pyrrole, to the four pyrroles destined to form rings A−D; 7 additional steps accrued to obtain the dipyrromethanes that constitute the Eastern and Western halves (Scheme 13, the step numbers are identical to those shown in ref 64.). The first step formed the Knorr pyrrole (in several kg quantities), the next 24 steps were divided into four parallel paths, whereas the remaining 21 steps proceeded in linear fashion. Remarkable features of the synthesis include the directed intramolecular joining (via an imine) of the Eastern and Western halves (step 33), construction of the acrylate Scheme 10. Hydrogenation of a Porphyrin to Form a Chlorin Scheme 11. Representative meso-Tetraarylchlorins Scheme 12. Methyl Pyropheophorbide a

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“…All the methodologies employed for the introduction of hydrogen: photochemical reduction, catalytic hydrogenation, the reduction with sodium and isoamyl alcohol, − and reduction with diimide , are based upon the fact that at least two of the double bonds of the porphyrin structure are not included in the 18 electron aromatic system. Thus, typical methods for reduction of isolated double bonds can be applied.…”

Section: Discussionmentioning

confidence: 99%

New Halogenated Phenylbacteriochlorins and Their Efficiency in Singlet-Oxygen Sensitization

et al. 2002

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Halogenated phenylbacteriochlorins are synthesized with high yields in a two-step procedure. They have strong absorbances in the red and are very stable to air and light at room temperature. Flash photolysis measurements show that the triplet states of these bacteriochlorins have 30 µs lifetimes in deaerated toluene, that are quenched with diffusion-controlled rate constants by molecular oxygen. Time-resolved photoacoustic measurements, with nanosecond and nanocalorie resolution, show that these bacteriochlorins sensitize the formation of singlet oxygen with nearly unity quantum yield. However, singlet-oxygen phosphorescence measurements indicate that physical quenching occurs before the singlet-oxygen molecules diffuse into solution, and nearly half of the sensitized singlet states are lost.

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Synthesis and Stereochemistry of Hydroporphyrins

Cited by 14 publications

References 187 publications

Protochlorophyllide oxidoreductase: A homology model examined by site‐directed mutagenesis

Protochlorophyllide oxidoreductase: A homology model examined by site‐directed mutagenesis

De NovoSynthesis of Gem-Dialkyl Chlorophyll Analogues for Probing and Emulating Our Green World

New Halogenated Phenylbacteriochlorins and Their Efficiency in Singlet-Oxygen Sensitization

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