| BackgroundIn recent decades,a large-scale of small molecule compound library,used to screen disease-related targets and discover effective lead compounds,has been established based on DNA encoded library（DEL）,which has become a potent technology for drug discovery.The success of DEL in identifying binders is due to its exceptional number and diverse chemotypes,introduced via on-DNA chemistry.However,traditional organic methods for compound synthesis are limited by DNA’s chemical reactivity,leaving a considerable portion of chemical space unexplored.Therefore it is urgently need to develop on-DNA chemistry with mild conditions,simplicity and high efficiency.C-H functionalization has emerged as an effective strategy due to its high efficiency and strong atom-/step-economy.N-phenoxyacetamide,as a novel reaction substrate containing an oxidizing directing group,can effectively avoid the use of an equivalent external oxidants.While significant progress has been made in developing N-phenoxyacetamide directed C-H functionalization,on-DNA C-H activation involving N-phenoxyacetamide has been unprecedented.As a result,developing practical methods for on-DNA C-H functionalization of N-phenoxyacetamides for the chemodivergent assembly is highly appealing.PurposeHere we obtain a series of on-DNA enamides and benzofurans as material basis for drug screening through diverse on-DNA compatible C-H activation of N-phenoxyacetamides with alkynes using various reaction modes,including Rh（III）-catalyzed C-H alkenylation,Ru（II）-catalyzed C-H annulation.At the same time,other on-DNA reactions directed by N-phenoxyacetamide were explored to provide more ideas and basis for DNA compatible reaction.Methods（1）By reacting different functional groups substituted N-phenoxyacetamide with HP-NH2 through HOAT,EDC,and DIPEA catalyzed amide condensation,a series of DNA-labeled substrates were successfully generated.（2）By using[Cp*Rh Cl2]2 or[Ru（p-cymene）Cl2]2 catalyzed C-H functionalization of DNA-labeled N-phenoxyacetamides with alkynes,optimizing related parameters and investigating the scope and generality of the reaction,a series of DNA-encoded compounds have been synthesized in one pot.（3）Explored the other on-DNA C-H functionalization of N-phenoxyacetamide.Simultaneously explored the later potential application of on-DNA C-H annulation of N-phenoxyacetamide.（4）The compatibility of the developed transition metal catalyzed on-DNA C-H bond activation reaction was verified by evaluating the degradation of the encoded DNA through DNA ligation,polyacrylamide gel electrophoresis,Sanger sequencing and q PCR experiments.Results（1）We have obtained a series of DNA-labeled N-phenoxyacetamide such as benzyl,para and meta DNA labeled N-phenoxyacetamide,DNA labeled tyrosine derivatives and DNA labeled butynic acid.（2）A series of DNA encoded phenols and benzofurans were obtained efficiently through transition metals catalyzed on-DNA compatible C-H functionalization under the optimized conditions.（3）A series of derivatization experiments of DNA-labeled N-phenoxyacetamide were carried out.DNA-labeled benzofuran backbone compounds were derivatized to generate DNA-encoded biologically active molecules,verifying the potential application of the on DNA C-H annulation.（4）Several experimental data characterize the integrity of the"barcoded"DNA and the reaction illustrates that the C-H functionalization reaction is compatible with DNA and also provides new chemical synthesis method of the construction of DEL.ConclusionsIn summary,this study developed diverse on-DNA C-H activation of N-phenoxyacetamides via different reaction modes.By exploring the effects of different coupling partners and catalytic conditions on reaction efficiency,a series of DNA encoded enamide and benzofuran compounds have been synthesized in one pot.Simultaneously transforming DNA encoded benzofuran compounds can synthesize diverse DNA encoded biologically active molecules.Later DNA degradation evaluation experiments illustrate that the C-H functionalization of N-phenoxyacetamide is compatible with DNA.This strategy about the C-H functionalization of N-phenoxyacetamide provides more ideas and basis for DNA compatible reaction and also laids the foundation for constructing a large-scale and structurally diverse DNA encoded library of enamides and benzofuran compounds. |
