The Bioorthogonal Ligation Of Isonitriles And Amines To Ureas

Urea and its derivatives constitute an important class of compounds,due to their applications in agrochemicals,dyes,antioxidants and anticancer,have attracted considerable attention from chemists.A bioorthogonal reaction for the synthesis of ureas from isonitriles and amines in neutral aqueous medium was developed,and fluorescence imaging of living cells has been achieved by the bioorthogonal isonitriles-amines ligation.The thesis consists of the following two mian parts.The classical bioorthogonal reactions and the new types of bioorthogonal reactions were summarized in the first chapter.Bioorthogonal reactions involving isonitriles were highlighted.Firstly,the bioorthogonal reaction of isonitriles and tetrazines was introduced.The effects of isonitrile or tetraazazine of different substituents on the efficiency of the bioorthogonal reaction and the stability of the products were illustrated.Secondly,the bis-labeling of bioorthogonal reaction partners composed of isonitriles and tetrazines with other types of bioorthogonal reactions such as SPAAC was introduced,indicating that bioorthogonal reactions could be orthogonal to each other.Then,the use of isonitrile derivatives as masking groups was introduced,indicating that biorthogonal cleavage reaction could be used to achieve targeted fluorescence activation or drug molecule release.Finally,the application of isonitriles and chlorooximes ligation as a new type of bioorthogonal reaction was introduced.The biological activities and an overview for the synthesis of ureas were summarized in the second chapter.A bioorthogonal reaction for synthesis of ureas from isonitriles and amines was introduced.In order to screen the optimum reaction condition,in this thesis,water was used as solvent to explore the reactions between isonitriles and amines.NCS was added to activate isonitriles,and adjust the p H value of the reaction solution to neutral with K₂CO₃,then the corresponding ureas could be efficiently and conveniently synthesized.Moreover,the reaction rate constant k₂ of the new method has been measured.After the optimized conditions were determined,the applicability of the substrate was investigated.The thesis found that aniline,aliphatic amine,amine group in drug molecules,amine sugar and amino acid were all suitable for the reaction condition,and the yield was up to 97%.The chemoselectivity of new method was preliminarily investigated by screening a series of substrates such as thiols,glycerols,glucose,amides,azo-containing heterocyclic rings and amino-containing bases.The biocompatibility of the new method was preliminarily investigated by using a mixture of water and phosphate buffer（PBS）and culture medium（DMEM）.Even with more complex peptide substrate,such as Human angiotensin II,we have observed specific urea formation.Finally,the thesis synthesized the urea derivative of 7-Hydroxy-2H-1-benzopyran-2-one by the reaction of its isonitrile derivative with amine.Furthermore,the new method has a good chemoselectivity and biocompatibility.Isonitrile-coumarin 47b was used as fluorescent probe,direct labeling of Ac₄Glc N has been achieved in Hep G2 cells,and the intensity of fluorescence showed concentration dependent.This bioorthogonal isonitriles-amines ligation has potential application in the field of bioorthogonal chemistry.