Fluorescent Orthopalladated Complexes of 4-Aryliden-5(4)-oxazolones from the Kaede Protein: Synthesis and Characterization.

The goal of the work reported here was to amplify the fluorescent properties of 4-aryliden-5(4)-oxazolones by suppression of the hula-twist non-radiative deactivation pathway. This aim was achieved by simultaneous bonding of a Pd center to the N atom of the heterocycle and the carbon of the arylidene ring. Two different 4-(()-arylidene)-2-(()-styryl)-5(4)-oxazolones, the structures of which are closely related to the chromophore of the Kaede protein and substituted at the 2- and 4-positions of the arylidene ring ( OMe; F), were used as starting materials.

Synthesis of esters of diaminotruxillic bis-amino acids by Pd-mediated photocycloaddition of analogs of the Kaede protein chromophore.

The stereoselective synthesis of truxillic bis-amino esters from polyfunctional oxazolones is reported. The reaction of 4-(()-arylidene)-2-()-styryl-5(4)-oxazolones with Pd(OAc) resulted in -palladation and the formation of a dinuclear open-book complexes with carboxylate bridges, where the Pd atom is C^N bonded to the oxazolone. In the two exocyclic C=C bonds of the oxazolone are in a face-to-face arrangement, which is optimal for their [2 + 2] photocycloaddition.

Pd-catalyzed directed ortho-C-H alkenylation of phenylalanine derivatives.

A practical Pd-catalyzed ortho-olefination of enantioenriched N-(SO2Py)-protected aryl-alanine and norephedrine derivatives with electron-deficient alkenes has been developed using N-fluoro-2,4,6-trimethylpyridinium triflate as the terminal oxidant. The reaction occurs efficiently with excellent monosubstitution selectivity and without loss of enantiopurity. This cross-coupling proved to be broad in scope, tolerating a variety of steric and electronic changes to both coupling partners.

Cyclopalladation and reactivity of amino esters through C-H bond activation: experimental, kinetic, and density functional theory mechanistic studies.

The orthopalladation, through C-H bond activation, of a large number of amino esters and amino phosphonates derived from phenylglycine, and having different substituents at the aryl ring and the C-α atom, as well as on the N-amine atom, has been studied. The experimental observations indicated an improvement in the yields of the orthopalladated compounds when the N-amine and/or the C-α atom are substituted, when compared with the unsubstituted methyl phenylglycinate derivatives. In contrast, substitutions at the aryl ring do not promote significant changes in the orthometalation results.

Synthesis of conformationally restricted glutamate and glutamine derivatives from carbonylation of orthopalladated phenylglycine derivatives.

A new method for the regioselective synthesis of 2-alkoxycarbonyl- and 2-(aminocarbonyl)phenylglycinate methyl esters has been developed. The reaction of the orthopalladated complex [Pd(μ-Cl)(C(6)H(4)(CH(CO(2)Me)NMe(2))-2)](2) (1) with nucleophiles HNu under a CO atmosphere results in the selective incorporation of the C(O)Nu moiety to the phenyl ring and formation of the carbonyl species ortho-C(6)H(4)(C(O)Nu)(CH(CO(2)Me)NMe(2)) (2a-j) (Nu = OR, NHR, NR(2)). Compounds 2a-j are conformationally restricted analogues of glutamic acid and glutamine and are interesting due to their biological and pharmacological properties.