Chemical Synthesis of Coelenterazine and Its Analogs: New Route toward Four Segment-Couplings
摘要:
A novel and improved synthetic route includes four segment-couplings toward coelenterazine and its analogs as luminescent molecules. Regio- and chemo-selective cross coupling reactions using palladium catalysts with 5-iodo-3-bromo-2-aminopyrazine have enabled providing various aminopyrazine derivatives having different substituents. The improved synthesis of coelenterazine and its analogs employed advanced condensation with the aminopyrazines using various keto-acetal segments, which resulted in much higher yields to give the final imidazopyrazinone heterocycles than the previous method using keto-aldehydes.
Synthesis of coelenterazine analogs is in recent demand to supply more luminescent compounds with reasonable stability as substrate for the photoprotein manipulated in a living cells or particular organelle. There are limited methods for the synthesis of 6-substituted coelenterazine due to the route and instability of the compounds under the existing conditions. This paper describes six examples including Suzuki-Miyaura cross coupling reaction with reactive triflate (unstable) and stable tosylate intermediates of the imidazo[1,2-a]pyrazin-3-one. Five examples of 2-amino-3-benzyl-5-O-Tf-pyrazine are also discussed. The product coelenterazine analogs are obtained in the form of dehydrocoelenterazine, which is the substrate of a squid photoprotein, symplectin. (C) 2010 Elsevier Ltd. All rights reserved.
Synthesis of Disubstituted Dithioethers: <i>tert</i>-Butoxide Promoted Elimination/Ring Opening of 1,3-Dithianes Followed by Palladium-Catalyzed C–S Bond Formation
作者:Nissa Abidi、Jason R. Schmink
DOI:10.1021/acs.joc.5b00547
日期:2015.4.17
We report the tandem base-promoted elimination/ring-opening of 2-benzyl-1,3-dithianes with subsequent cross coupling of the pendent thiol with a range of aryl bromides. A simple Pd(OAc)(2)/Xantphos catalyst system affects this new reaction and is compatible with a wide range of functional groups, including heteroaromatic coupling partners. The transformation proceeds in good to excellent yields (6999%) and exhibits strong stereoselectivity, forming the E-alkene as the major diastereomer. This new methodology provides access to nonsymmetric propylene styryl/aryl dithioethers, a previously undisclosed motif.
Chemical Synthesis of Coelenterazine and Its Analogs: New Route toward Four Segment-Couplings
A novel and improved synthetic route includes four segment-couplings toward coelenterazine and its analogs as luminescent molecules. Regio- and chemo-selective cross coupling reactions using palladium catalysts with 5-iodo-3-bromo-2-aminopyrazine have enabled providing various aminopyrazine derivatives having different substituents. The improved synthesis of coelenterazine and its analogs employed advanced condensation with the aminopyrazines using various keto-acetal segments, which resulted in much higher yields to give the final imidazopyrazinone heterocycles than the previous method using keto-aldehydes.
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