title: Mild and nonracemizing conditions for Ullmann-type diaryl ether formation between aryl iodides and tyrosine derivatives.
abstract: CuI/N,N-dimethylglycine-catalyzed coupling reaction of L-tyrosine derivatives and L-phenylalanine-derived iodides in the presence of Cs2CO3 works at 90 degrees C to provide the corresponding diaryl ether. Partial racemization occurs when N-Boc- and N-Cbz-protected aromatic amino esters are used, while N-trityl- and N,N-dibenzyl-protected aromatic amino esters give rise to coupling products without loss of optical purity. Little racemization is also observed in cases of N-Boc- and N-Cbz-protected aromatic amino acids as substrates. But their reaction yields are moderate. On the basis of these studies, shorter protocols for assembling (S,S)-isodityrosine and K-13 are developed.
authors.affiliation: State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Cai
authors.forename: Gang
authors.initials: G
authors.lastname: He
authors.forename: Dawei
authors.initials: D
authors.lastname: Ma
mesh_terms: D002384:Catalysis; D003300:Copper / Q000737:chemistry; D004987:Ethers / Q000138:chemical synthesis* / Q000737:chemistry; D006847:Hydrocarbons, Iodinated / Q000737:chemistry*; D007454:Iodides / Q000737:chemistry; D015394:Molecular Structure; D012521:Sarcosine / Q000031:analogs & derivatives / Q000737:chemistry; D013237:Stereoisomerism; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry*
chemical_list: D004987:Ethers; D006847:Hydrocarbons, Iodinated; D007454:Iodides; D014443:Tyrosine; C025138:dimethylglycine; D003300:Copper; C073870:cuprous iodide; D012521:Sarcosine