- Engineering Orthogonal Methyltransferases to Create Alternative Bioalkylation Pathways
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S-adenosyl-l-methionine (SAM)-dependent methyltransferases (MTs) catalyse the methylation of a vast array of small metabolites and biomacromolecules. Recently, rare carboxymethylation pathways have been discovered, including carboxymethyltransferase enzymes that utilise a carboxy-SAM (cxSAM) cofactor generated from SAM by a cxSAM synthase (CmoA). We show how MT enzymes can utilise cxSAM to catalyse carboxymethylation of tetrahydroisoquinoline (THIQ) and catechol substrates. Site-directed mutagenesis was used to create orthogonal MTs possessing improved catalytic activity and selectivity for cxSAM, with subsequent coupling to CmoA resulting in more efficient and selective carboxymethylation. An enzymatic approach was also developed to generate a previously undescribed co-factor, carboxy-S-adenosyl-l-ethionine (cxSAE), thereby enabling the stereoselective transfer of a chiral 1-carboxyethyl group to the substrate.
- Bennett, Matthew R.,Cronin, Victoria A.,Herbert, Abigail J.,Micklefield, Jason,Shepherd, Sarah A.,Sung, Rehana
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supporting information
p. 14950 - 14956
(2020/07/04)
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- Application of hexamethylenetetramine in a Pictet-Spengler type reaction for synthesis of isoquinoline derivatives
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Hexamethylenetetramine was used successfully as amino- and amidoalkylation cyclization reagent for the synthesis of 3,4-dihydroisoquinolines, tetrahydroisoquinolines and 1,4-dihydro-3(2H)-isoquinolinones. The reagent provides a simple and convenient pathway for the preparation of a range of these compounds.
- Ivanov, Iliyan,Venkov, Atanas
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p. 1569 - 1580
(2007/10/03)
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- Synthesis of phthalideisoquinoline and protoberberine alkaloids and indolo[2,1-α]isoquinolines in a divergent route involving palladium(0)- catalyzed carbonylation
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6,7,3',4'-Alkoxy-substituted 1-(2'-bromobenzoyl)-3,4-dihydroisoquinoline methiodides 17 were treated with sodium borohydride in methanol or acetic acid to give erythro-1-(2'-bromo-α-hydroxybenzyl)-2-methyl-1,2,3,4- tetrahydroisoquinolines 19. Treatment of 17 with lithium aluminum hydride in tetrahydrofuran gave the threo-isomer 20 in preference to the erythro 19. On the basis of studies on palladium(0)-catalyzed carbonylation of 2-bromo-3,4- dimethoxybenzyl alcohol to 6,7-dimethoxyphthalide, amino alcohol 19 or 20 was treated with a catalytic amount of palladium(II) acetate and triphenylphosphine in an atmosphere of carbon monoxide in the presence of chlorotrimethylsilane and potassium carbonate in boiling toluene to give the corresponding erythro- or threo-types of phthalideisoquinoline alkaloids 1 or 2, respectively. One-pot cyclization of the erythro-amino alcohols 19 was achieved by heating in N,N-dimethylformamide containing potassium carbonate to give 2,3,8,9- or 2,3,9,10-alkoxy-substituted 5,6-dihydroindolo[2,1- α]isoquinolines 3, which have a unique tetracyclic skeleton characteristic of dibenzopyrrocoline alkaloids. Similarly, palladium-(0)-catalyzed carbonylation of 1-(2'-bromobenzyl)tetrahydroisoquinolines 21 in the presence of excess potassium carbonate was found to give 8-oxoberbines 22, which on reduction with lithium aluminum hydride can be converted to protoberberine alkaloids 4.
- Orito, Kazuhiko,Miyazawa, Mamoru,Kanbayashi, Ryo,Tokuda, Masao,Suginome, Hiroshi
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p. 6583 - 6596
(2007/10/03)
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- BIOMIMETIC OXIDATIONS OF BENZYLISOQUINOLINE ALKALOUDS. II. THE BIS(SALICYLALDEHYDE)ETHYLENEDIIMINECOBALT(II)-CATALYZED OXIDATION OF BENZYLISOQUINOLINES WITH OXYGEN
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The complex bis(salicylaldehyde)ethylenediiminecobalt(II) (CoII salen) catalyzes the oxidation of benzylisoquinoline alkaloids with oxygen.Aminium radicals are formed and give rise to 1,2-dehydrobenzylisoquinoline ions.Cleavage of the C(1)-C(9) bond via C(9) oxidation is observed in some instances.
- Canonica, Luigi,Galliani, Guido,Nali, Micaela,Rindone, Bruno,Tollari, Stefano
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- BIOMIMETIC OXIDATIONS OF BENZYLISOQUINOLINE ALKALOUDS. I. THE PEROXIDASE AND ASCORBIC OXIDASE-CATALYSED OXIDATION
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The enzyme peroxidase behaves as a mixed-function oxidase toward the benzylisoquinoline alkaloid nucleus, giving rise to various phenoxy radicals depending on the substrate.These give either C(4) hydroxylation or C(5') hydroxylation and cyclisation to an aporphine, or cleavage of the C(1)-C(9) bond.
- Canonica, Luigi,Nali, Micaela,Rindone, Bruno,Tollari, Stefano,Marchesini, Augusto
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- Evidence for a Radical Chain Mechanism for the Knabe Reaction of 1,2-Dihydro-2-methylpapaverine
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A free radical chain mechanism is proposed for the Knabe reaction and the accompanying elimination reaction on account of their nonintegral reaction order and of successful inhibition experiments. 3,4-Dimethoxybenzyl radicals are the chain carrying species.Battersby's synthesis of N-methylpavine (19) from 1,2-dihydro-2-methylpapaverine (9) is dependent on the presence of formic acid as radical chain inhibitor.In the presence of inhibitors 1-benzyl-1,4-dihydro-2-methylisoquinolinium ions like 10 are persistent species whose chemistry can now be investigated.
- Langhals, Elke,Langhals, Heinz,Ruechardt, Christoph
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p. 1436 - 1454
(2007/10/02)
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- Electrochemical Oxidation of Aromatic Ethers. Part 8. Evidence of Homogeneous Electron Transfer during the 'Low Potential' Oxidation of Laudanosine
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Photolysis of N-amino- and N-nitroso-derivatives of 1,2,3,4-tetrahydropapaverine fails to produce aryl-aryl coupled products analogous to O-methylflavinantine.Instead both the 1- and 2-substituents of the heterocyclic ring are cleaved to give 6,7-dimethoxy-3,4-dihydroisoquinolines and veratraldehyde, the latter being an oxidation product of the 3,4-dimethoxybenzyl radical and/or cation.From this evidence, and the results of an electrolysis experiment carried out at high dilution, it is considered that the anodic cyclisation of laudanosine to O-methylflavinantine proceeds through homogeneous electron transfer rather than via homoconjugative activation within the intermediate radical cation as proposed by other workers.
- Hutchins, Michael,Sainsbury, Malcolm,Scopes, David I. C.
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p. 2059 - 2064
(2007/10/02)
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