Synthesis of Fmoc-Protected Arylphenylalanines (Bip Derivatives) via Nonaqueous Suzuki-Miyaura Cross-Coupling Reactions

Fluorescent α-amino acids via Heck-Matsuda reactions of phenylalanine-derived arenediazonium salts

The Heck-Matsuda coupling reaction of arenediazonium salts derived from L-phenylalanine with various alkenes has been developed. A two-step process involving the preparation of a tetrafluoroborate diazonium salt from a 4-aminophenylalanine derivative, followed by a palladium(0)-catalysed Heck-Matsuda coupling reaction allowed access to a range of unnatural α-amino acids with cinnamate, vinylsulfone and stilbene side-chains. Analysis of the photophysical properties of these unnatural α-amino acids demonstrated that the (E)-stilbene analogues exhibited fluorescent properties with red-shifted absorption and emission spectra and larger quantum yields than L-phenylalanine.

Solid-Phase Synthesis of Biaryl Cyclic Lipopeptides Derived from Arylomycins

An efficient approach for the solid-phase synthesis of N-methylated tailed biaryl cyclic lipopeptides based on the structure of arylomycins was established. Each of these analogues incorporates an N-terminal linear lipopeptide attached to a biaryl cyclic tripeptide containing a Phe-Tyr, a Tyr-Tyr, or a His-Tyr linkage. This methodology first involved an intramolecular Suzuki-Miyaura arylation of a linear peptidyl resin incorporating the corresponding halogenated amino acid at the N-terminus and a boronotyrosine at the C-terminus. After N-methylation of the resulting biaryl cyclic peptidyl resin, the N-methylated lipopeptidyl tail was then assembled. The biaryl cyclic lipopeptides were purified and characterized.

Approaches to Obtaining Fluorinated α-Amino Acids

Fluorine does not belong to the pool of chemical elements that nature uses to build organic matter. However, chemists have exploited the unique properties of fluorine and produced countless fluoro-organic compounds without which our everyday lives would be unimaginable. The incorporation of fluorine into amino acids established a completely new class of amino acids and their properties, and those of the biopolymers constructed from them are extremely interesting. Increasing interest in this class of amino acids caused the demand for robust and stereoselective synthetic protocols that enable straightforward access to these building blocks. Herein, we present a comprehensive account of the literature in this field going back to 1995. We place special emphasis on a particular fluorination strategy. The four main sections describe fluorinated versions of alkyl, cyclic, aromatic amino acids, and also nickel-complexes to access them. We progress by one carbon unit increments. Special cases of amino acids for which there is no natural counterpart are described at the end of each section. Synthetic access to each of the amino acids is summarized in form of a table at the end of this article with the aim to make the information easily accessible to the reader.

Mild, Aqueous α-Arylation of Ketones: Towards New Diversification Tools for Halogenated Metabolites and Drug Molecules

The palladium-catalysed aqueous α-arylation of ketones was developed and tested for a large variety of reaction partners. These mild conditions enabled the coupling of aryl/alkyl-ketones with N-protected halotryptophans, heterocyclic haloarenes, and challenging base-sensitive compounds. The synthetic potential of this new methodology for the diversification of complex bioactive molecules was exemplified by derivatising prochlorperazine. The methodology is mild, aqueous and flexible, representing a means of functionalizing a wide range of halo-aromatics and therefore has the potential to be extended to complex molecule diversification.