DOPA Derivatives Research Articles

Convenient synthesis of acetonide-protected 3,4-dihydroxyphenylalanine (DOPA) for Fmoc solid-phase peptide synthesis

We report a facile approach to the synthesis of acetonide and Fmoc-protected 3,4-dihydroxyphenylalanine (DOPA), Fmoc-DOPA(acetonide)-OH. By protecting the amino group of DOPA with a phthaloyl group and the carboxyl group as a methyl ester, acetonide protection of the catechol of DOPA derivative was realized in the presence of p-toluenesulfonic acid. Following removal of protecting groups, the intermediate was converted to Fmoc-DOPA(acetonide)-OH, which was successfully incorporated into a short DOPA-containing peptide, derived from marine tubeworm cement proteins Pc1 and Pc2.

Pigments of Fly Agaric (Amanita muscaria)

The complex pigment pattern of fly agaric (Amanita muscaria) cap skins has been studied by LC-DAD and mass spectrometry. Among the betaxanthins the corresponding derivatives of serine, threonine, ethanolamine, alanine, Dopa, phenylalanine and tryptophan are reported for the first time to contribute to the pigment pattern of fly agarics. Betalamic acid, the chromophoric precursor of betaxanthins and betacyanins, muscaflavin and seco-dopas were also detected. Furthermore, the red-purple muscapurpurin and the red muscarubrin were tentatively assigned while further six betacyanin-like components could not be structurally allocated. Stability studies indicated a high susceptibility of pigment extracts to degradation which led to rapid colour loss thus rendering a complete characterization of betacyanin-like compounds impossible at present. Taking into account these difficulties the presented results may be a starting point for a comprehensive characterization of the pigment composition of fly agarics.

Diastereoselective Intramolecular α-Amidoalkylation Reactions of l-DOPA Derivatives. Asymmetric Synthesis of Pyrrolo[2,1-a]isoquinolines

[reaction: see text] Stereocontrolled intramolecular alpha-amidoalkylation reactions of L-DOPA-derived succinimides have been studied. Addition of MeLi to nonracemic succinimides 9a-d yields oxoamides, which are cyclized upon treatment with Lewis or protic acids to afford (5S,10bS)-trans 11 or (5S,10bR)-cis 12pyrroloisoquinolines with variable diastereoselectivities, but with high enantiomerical purities (ee 99%).

Synthesis of the Side Chain Cross-Linked Tyrosine Oligomers Dityrosine, Trityrosine, and Pulcherosine

[reaction: see text] An efficient synthesis of dityrosine and the first syntheses of the tyrosine trimers trityrosine and pulcherosine have been achieved. Protected 3-iodotyrosine underwent tandem Miyaura borylation-Suzuki coupling to give protected dityrosine. The choice of benzyl carbamate, ester, and ether protecting groups enabled a one-step global deprotection to give dityrosine. Suzuki coupling of protected 3,5-diiodotyrosine and tyrosine-3-boronic acid derivatives gave the corresponding trityrosine, but in low yield. However, use of a potassium tyrosine-3-trifluoroborate derivative in place of the corresponding pinacol boronate ester, in combination with protecting group variation, gave protected trityrosine in good yield. Access to pulcherosine was achieved through copper-catalyzed coupling of phenylalanine-4-boronic acid and 4-O-protected dopa derivatives to give an isodityrosine derivative. Selective halogenation followed by Suzuki coupling with the potassium tyrosine-3-trifluoroborate gave protected pulcherosine. Global deprotection of the protected trityrosine and pulcherosine derivatives completed the first syntheses of the corresponding tris-alpha-amino acids.

Structural Investigation of 3,4-Dihydroxyphenylalanine-Terminated Propanethiol Assembled on Gold

3,4-Dihydroxyphenylalanine-terminated propanethiol (DOPA-PT), an amino acid DOPA linked to 3-mercaptopropionic acid through an amide bond, is adsorbed and self-assembled to polycrystalline gold surfaces. The structure of the adsorbates was characterized by means of X-ray photoelectron spectroscopy (XPS), infrared reflection−absorption spectroscopy (IRAS), and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Strong molecular binding of a DOPA derivative on gold surfaces through the sulfur atom was attained. Angle-dependent XPS results showed that the aromatic ring is oriented away from the gold surface. Both IRAS and NEXAFS results showed parallel orientation of the CO bond of the amide moiety relative to the gold surface. Hydrogen bonding between amide moieties is achieved, and it seemed to provide additional orientation stabilization. Deduced orientation of the amide moiety on the short alkyl chain (or the peptide plane) is assumed to give the average orientation of the main molecular axis. The main molecular axis is estimated to have an average tilt angle of approximately 37° relative to the gold surface normal based on NEXAFS results. The aromatic ring exhibits a preferred orientation with an average tilt angle of about 64°. The experimental results showed that DOPA-thiol with amide linkage is able to self-assemble and form a layered structured film consisting of a layer of alkane chains with a gauche conformation beneath an oriented layer of DOPA.

Synthesis of peptides containing DOPA (3,4-dihydroxyphenylalanine)

Proteins from coral reefs structures, eggshells, and marine mollusk adhesives all contain the amino acid 3,4-dihydroxyphenylalanine (DOPA). The insoluble nature of these materials has hampered characterization and turned our efforts toward work with small peptide mimics. In this paper, we present the syntheses of various DOPA derivatives: Boc-DOPA, Fmoc-DOPA, DOPA(TBDMS) 2, DOPA(TBDPS) 2, Boc-DOPA(TBDPS) 2, Fmoc-DOPA(TBDMS) 2, and Fmoc-DOPA(TBDPS) 2 (where Boc= tert-butyloxycarbonyl, Fmoc=9-fluorenylmethyloxycarbonyl, TBDMS= tert-butyldimethylsilyl, and TBDPS= tert-butyldiphenylsilyl). These DOPA compounds were used to prepare peptides of various sequences. The synthetic procedure described provides an efficient route to DOPA-containing peptides in which sidechain deprotection and cleavage from resin can be accomplished in one step.

In vitro polymerization of mussel polyphenolic proteins catalyzed by mushroom tyrosinase

The in vitro enzymatic polymerization of the polyphenolic protein purified from the mussels Aulacomya ater, Mytilus edulis chilensis and Choromytilus chorus was studied. Mushroom tyrosinase was used to oxidize the dopa residues present in these proteins, and polymerization was monitored by acid-urea polyacrylamide gel electrophoresis. The protein from A. ater polymerized at a faster rate than the other two. Amino acid analysis of the crosslinked protein showed a notable decrease in the content of dopa, but no significant change of other amino acids. This suggests that crosslink formation may be limited to the oxidized dopa derivatives of the protein molecules.

An improved synthesis of selectively protected L-dopa derivatives from L-tyrosine.

An improved synthesis of selectively protected L-dopa derivatives from L-tyrosine.

Tyrosine hydroxylase is inactivated by catechol-quinones and converted to a redox-cycling quinoprotein: possible relevance to Parkinson's disease.

Quinone derivatives of DOPA, dopamine, and N-acetyldopamine inactivate tyrosine hydroxylase, the initial and rate-limiting enzyme in the biosynthesis of the catecholamine neurotransmitters. The parent catechols are inert in this capacity. The effects of the catecholquinones on tyrosine hydroxylase are prevented by antioxidants and reducing reagents but not by scavengers of hydrogen peroxide, hydroxyl radicals, or superoxide radicals. Quinone modification of tyrosine hydroxylase modifies enzyme sulfhydryl groups and results in the formation of cysteinyl-catechols within the enzyme. Catecholquinones convert tyrosine hydroxylase to a redox-cycling quinoprotein. Quinotyrosine hydroxylase causes the reduction of the transition metals iron and copper and may therefore contribute to Fenton-like reactions and oxidative stress in neurons. The discovery that a phenotypic marker for catecholamine neurons can be converted into a redox-active species is highly relevant for neurodegenerative conditions such as Parkinson's disease.

Stereoselective Inclusion of DOPA Derivatives by a Self-Assembled Monolayer of Thiolated Cyclodextrin on a Gold Electrode

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTStereoselective Inclusion of DOPA Derivatives by a Self-Assembled Monolayer of Thiolated Cyclodextrin on a Gold Electrode†Teruo Fukuda, Yasushi Maeda, and Hiromi KitanoView Author Information Department of Chemical and Biochemical Engineering, Toyama University, Toyama 930-8555, Japan Cite this: Langmuir 1999, 15, 5, 1887–1890Publication Date (Web):February 2, 1999Publication History Received16 September 1998Revised27 November 1998Published online2 February 1999Published inissue 1 March 1999https://doi.org/10.1021/la981269nCopyright © 1999 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views618Altmetric-Citations79LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (115 KB) Get e-AlertsSUBJECTS:Cavities,Complexation,Electrodes,Gold,Reaction products Get e-Alerts

Synergistic induction of DNA strand breakage caused by nitric oxide together with catecholamine: implications for neurodegenerative disease.

Oxidative damage in neuronal cells and DNA has been implicated in the pathogenesis of various neurodegenerative diseases. We have demonstrated that DNA strand breakage is induced synergistically when plasmid DNA is incubated in the presence of both an NO-releasing compound (diethylamine NONOate, spermine NONOate, sodium nitroprusside) and a catecholamine (e.g., L-DOPA, dopamine, etc.). Either an NO-releasing compound or a catecholamine alone induced much fewer strand breaks. Tyrosine and tyramine as well as O-methylated derivatives of DOPA and dopamines did not exert this synergistic effect in the presence of NO. The DNA strand breakage induced by NO plus dopamine was inhibited by carboxy-PTIO (a trapping agent of NO and possibly other radicals), superoxide dismutase, and antioxidants such as N-acetylcysteine and ascorbate but not by HO. scavengers such as dimethyl sulfoxide, ethanol, and D-mannitol. These results suggest that the free HO. is not involved; rather a new oxidant(s) formed by the reaction between NO and catecholamine could be responsible for causing the DNA strand breakage. We propose that one of the responsible compounds is peroxynitrite (ONOO-), which is a strong oxidant and nitrating agent formed by the reaction between NO and O2.-. NO has been shown to oxidize catecholamines to form quinone derivatives, which lead to the generation of O2.- by the quinone/hydroquinone redox system. O2.- then reacts rapidly with NO to form peroxynitrite. However, it is also possible that other compounds such as NOx generated from catecholamines and NO may cause DNA damage. Our results implicate a synergistic interaction of catecholamines formed in dopaminergic neurons and NO formed by microglia or astrocytes or the two compounds produced within the same neuronal cells to produce a potent oxidant(s) which could cause damage in cells and DNA, thus playing an important role in the pathogenesis of various neurodegenerative diseases.

Efficient Synthesis of Selectively Protected l-Dopa Derivatives from l-Tyrosine via Reimer−Tiemann and Dakin Reactions

Efficient Synthesis of Selectively Protected <scp>l</scp>-Dopa Derivatives from <scp>l</scp>-Tyrosine via Reimer−Tiemann and Dakin Reactions

Synthesis of polymer-bound 6-mercuric carboxylate DOPA precursors and solid phase labelling method of 6-radioiodinated l-DOPA

In order to avoid separating unreacted mercury precursor and other mercury-containing compounds after the halodemercuration of a 6-mercury DOPA precursor, we developed a polymer-bound mercury precursor for the preparation of 6-halogenated DOPA. In this study, polymer-bound 6-mercuric carboxylate DOPA derivatives were synthesized from ion-exchange resin and Merrifield-type resin. Iododemercuration of polymer-bound 6-mercuric carboxylate DOPA derivatives gave higher yields (49–54%) compared with monomeric 6-mercuric trifluoroacetate protected DOPA. The radioiodination of the resin with no-carrier added iodine-125 afforded protected 6-[ 125I]I- l-DOPA with labelling efficiency of 92–97% with both polymer-bound 6-mercuric carboxylate DOPA derivatives.

Model sclerotization studies. 3. Cuticular enzyme catalyzed oxidation of peptidyl model tyrosine and dopa derivatives

Incubation of N-acetyltyrosine methyl ester with cuticular enzymes, isolated from the wandering stages of Calliphora sp larvae, resulted in the generation of N-acetyldopa methyl ester when the reaction was carried out in the presence of ascorbate which prevented further oxidation of the o-diphenolic product. Enzymatic oxidation of N-acetyldopa methyl ester ultimately generated dehydro N-acetyldopa methyl ester. The identity of enzymatically produced N-acetyldopa methyl ester and dehydro N-acetyldopa methyl ester has been confirmed by comparison of the ultraviolet and infrared spectral and chromatographic properties with those of authentic samples as well as by nuclear magnetic resonance studies. Since N-acetyldopaquinone methyl ester was also converted to dehydro N-acetyldopa methyl ester and tyrosinase was responsible for the oxidation of N-acetyldopa methyl ester, a scheme for the cuticular phenoloxidase catalyzed conversion of N-acetyltyrosine methyl ester to dehydro N-acetyldopa methyl ester involving the intermediary formation of the quinone and the quinone methide is proposed to account for the observed results. The conversion of N-acetyldopa methyl ester to dehydro derivative remarkably resembles the conversion of the sclerotizing precursor, N-acetyldopamine, to dehydro-N-acetyldopamine observed in the insect cuticle. Based on these comparative studies, it is proposed that peptidyl dopa derivatives could also serve as the sclerotizing precursors for the sclerotization of the insect cuticle.

Synthesis of polymer-bound 6-thiolatomercury and 6-mercuric sulfonate DOPA precursors and their halodemercuration reactivity

Fluorodemercuration has the greatest utility for the preparation of 6-[ 18F]DOPA, but requires separation from unreacted mercury precursor and other mercury-containing compounds. One approach is the development of a polymer-bound mercury precursor. In this study, polymer-bound 6-thiolatomercury and 6-mercuric sulfonate DOPA derivatives, and its monomeric analogs were synthesized. Fluorodemercuration of monomeric analog of mercuric sulfonate gave half the yield (14–15%) while iododemercuration gave the same yield (38%) compared with a 6-mercuric trifluoroacetate protected DOPA. The mercuric sulfonate undergoes halodemercuration, so polymer-bound halodemercuration precursors may be useful as precursors of 6-[ 18F]DOPA.

The effect of oxygen on melanin precursors released from retinal pigment epithelial cells in vitro.

The autoxidation of dopa to melanin in culture media causes toxicity to retinal pigment epithelial (RPE) cells and endothelial cells. The damage is specific to cell type and to the ambient oxygen concentration. To determine whether RPE cells influence the oxidation of dopa to media, we compared light absorbing dopa derivatives in the media exposed to cells with those found in the media incubated without cells. Dopa was extensively oxidized in the presence of RPE cells, and more light absorbing substances were generated with higher dopa and oxygen concentrations. However, an increase in ambient oxygen concentration decreased the quantity of several dopa derivatives which had been formed. The data provided evidence that RPE modulated dopa metabolism. Quinolic derivatives produced from a tyrosinase reaction and dopa-melanin formation moved the peak absorbance wavelength of dopa into the visible range. The spectrum between the dopa-derived compounds in the media has an absorbance at 240-275 nm and a maximum around 300 nm with a shoulder near 375 nm. Gaussian analysis (peak separation) resolved these spectra into five components: a sharp band at 248 nm, a band at 295 nm, a large band at 359 nm, and two broad bands at 459 and 585 nm.

Regioselective radiofluorodestannylation with [ 18F]F 2 and [ 18F]CH 3COOF: A high yield synthesis of 6-[ 18F]fluoro- l-dopa

A protected 6-trimethylstannyl dopa derivative 6 has been synthesized for the first time as a precursor for the preparation of 6-[ 18F]fluoro- l-dopa. The tin derivative 6 readily reacted with electrophilic radiofluorinating agents such as [ 18F]F 2 and [ 18F]AcOF. The [ 18F]fluoro intermediate 7 was easily hydrolyzed with HBr and the product 6-[ 18F]fluoro- l-dopa was isolated after HPLC purification in a maximum radiochemical yield of 25%, ready for human use. The various intermediates, the stannyl precursor 6 and the final product (after 18F decay) were all fully characterized by 1H, 13C, 19F and 119Sn NMR as well as high resolution mass spectroscopy.

Direct enantiomeric separation of phenylalanine, DOPA and their intermediates by supercritical fluid chromatography

Phenylalanine (Phe), 3-(3,4-dihydroxyphenyl)alanine (DOPA) and their corresponding intermediates [N-acyl alkyl esters of Phe, DOPA, 3-(3,4-dimethoxylphenyl)alanine, 3-(3-methoxyl-4-hydroxyphenyl)alanine and 3-(3,4-methylenedioxyphenyl)alanine] were enantiomerically separated by supercritical fluid chromatography with carbon dioxide as the mobile phase in a cross-linked polycyanoethyl vinyl siloxane, l-Val- tert.-butylamide fused-silica capillary column. The effects of substituents in the benzene ring and the acyl and alkyl groups of the intermediates or derivatives of Phe and DOPA on enantioselectivity were investigated. The optical purities of some intermediates of Phe and DOPA were determined.

Conformational analysis and aqueous hydration studies of model peptides for the adhesive protein of the mussel, Mytilus edulis L

Conformations of model peptides of the adhesive protein of the mussel, Mytilus edulis L were investigated using molecular mechanics. The protein structure was represented as the repeat of a 10-residue unit. This decamer, and di- and tri-decamers of it, were considered in the modeling. Incorporation of the unusual dopamine residue in the decamer repeat may be explained by its hydrogen bond forming ability via its 3-OH group to a proline carbonyl oxygen. This bond contributes to maintaining a double reverse beta-turn structure in the decamer. This conformation was found more stable than 3(1) and alpha helical conformations. Adjacent reverse beta-turn structures are connected by short segments (2 to 3 residues) having little conformational preference. Thus, the overall protein can possess a significant random nature, yet have a highly ordered embedded conformational component. Hydrophilic character is in line with the larger number of OH groups on the phenyl ring for residue 9 (the site of the Dopa residue). The dehydration free energy of the (3-OH)-Phe as compared to the Dopa derivative is less by 1.4 kcal per decamer unit. This amounts to more than 100 kcal energy gain in the dehydration process for the total protein.

αβ-Dehydro-3,4-dihydroxyphenylalanine derivatives: Rate and mechanism of formation

The amino acid l-3,4-dihydroxyphenylalanine (DOPA), when present in the primary sequence of proteins, does not form melanin upon oxidation to the quinone, since its amine moiety participates in a peptide bond and cannot undergo internal cyclization. Instead, peptidyl DOPA quinone is available for other reactions. We have investigated the oxidation chemistry of a low molecular weight peptidyl DOPA analog, N-acetylDOPA ethyl ester (NAcDEE), and have shown that a major product of oxidation is an unsaturated DOPA derivative, N-acetyl-α,β-dehydroDOPA ethyl ester (NAcΔDEE) (see companion paper, Rzepecki et al., Arch. Biochem. Biophys. (1991) 285, 17–26 . In the present study, we have explored kinetic and mechanistic features of the conversion of NAcDEE to NAcΔDEE and found that the reaction requires: (i) oxidation of NAcDEE to the quinone, (ii) the presence of a Lewis base as a catalyst (phosphate anion was the best of those tried in the pH range 6.0–8.0), and (iii) prevention of competing reactions such as Michael additions. Conversion efficiencies in the presence of Lewis bases ranged between 12 and 19% at pH 8.0 and 35 and 90% at pH 6.0. At least two separate reaction mechanisms appeared necessary to explain the kinetic data: (i) a pseudo-first-order mechanism at pH 6.0 and above, and (ii) an additional second-order mechanism at higher pH which involved both NAcDEE catechol and quinone. The apparent pseudo-first-order rate constants increased with pH from 2.36 × 10 −4 s −1 at pH 6.0 to about 30 × 10 −4 s −1 at pH 8.0 in 0.1 m sodium phosphate. Tautomerization of DOPA quinone to dehydroDOPA may thus be a factor in the sclerotization of natural structures incorporating DOPA containing proteins.