217326-89-1Relevant articles and documents
2-[ 18 F]Fluorophenylalanine: Synthesis by Nucleophilic 18 F-Fluorination and Preliminary Biological Evaluation
Modemann, Daniel J.,Zlatopolskiy, Boris D.,Urusova, Elizaveta A.,Zischler, Johannes,Craig, Austin,Ermert, Johannes,Guliyev, Mehrab,Endepols, Heike,Neumaier, Bernd
, p. 664 - 676 (2019/01/23)
2-[ 18 F]Fluorophenylalanine (2-[ 18 F]FPhe), a promising PET tracer for imaging of cerebral infarction and tumors, was efficiently prepared from an easily accessible iodonium salt precursor using Cu-mediated radiofluorination under 'low base' or 'minimalist' conditions. Whereas significant racemization was initially observed if the 'minimalist' protocol was applied for radiolabeling, it was completely suppressed by the careful adjustment of 18 F - preprocessing. The initial biological study revealed a higher uptake of 2-[ 18 F]FPhe in different tumor cells in comparison to that of [ 18 F]FET. In contrast to 4-[ 18 F]FPhe, which suffered from rapid defluorination in vivo, 2-[ 18 F]FPhe demonstrated a sufficient in vivo stability. Conclusively, 2-[ 18 F]FPhe is a promising PET probe that is now readily available using Cu-mediated radiofluorination under 'minimalist' or 'low base' conditions. The simplicity of the translation of the proposed procedures to automated synthesis modules allows a broad biological evaluation of 2-[ 18 F]FPhe. Notably, a novel protocol for the preparation of N -Boc protected amino acids from the respective Ni-Schiff base complexes was developed that avoided application of strongly acidic conditions.
4R- and 4S-iodophenyl hydroxyproline, 4R-pentynoyl hydroxyproline, and S-propargyl-4-thiolphenylalanine: Conformationally biased and tunable amino acids for bioorthogonal reactions
Forbes, Christina R.,Pandey, Anil K.,Ganguly, Himal K.,Yap, Glenn P. A.,Zondlo, Neal J.
supporting information, p. 2327 - 2346 (2016/03/01)
Bioorthogonal reactions allow the introduction of new functionalities into peptides, proteins, and other biological molecules. The most readily accessible amino acids for bioorthogonal reactions have modest conformational preferences or bases for molecular interactions. Herein we describe the synthesis of 4 novel amino acids containing functional groups for bioorthogonal reactions. (2S,4R)- and (2S,4S)-iodophenyl ethers of hydroxyproline are capable of modification via rapid, specific Suzuki and Sonogashira reactions in water. The synthesis of these amino acids, as Boc-, Fmoc- and free amino acids, was achieved through succinct sequences. These amino acids exhibit well-defined conformational preferences, with the 4S-iodophenyl hydroxyproline crystallographically exhibiting β-turn (φ, ψ ～ -80°, 0°) or relatively extended (φ, ψ ～ -80°, +170°) conformations, while the 4R-diastereomer prefers a more compact conformation (φ ～ -60°). The aryloxyproline diastereomers present the aryl groups in a highly divergent manner, suggesting their stereospecific use in molecular design, medicinal chemistry, and catalysis. Thus, the 4R- and 4S-iodophenyl hydroxyprolines can be differentially applied in distinct structural contexts. The pentynoate ester of 4R-hydroxyproline introduces an alkyne functional group within an amino acid that prefers compact conformations. The propargyl thioether of 4-thiolphenylalanine was synthesized via copper-mediated cross-coupling reaction of thioacetic acid with protected 4-iodophenylalanine, followed by thiolysis and alkylation. This amino acid combines an alkyne functional group with an aromatic amino acid and the ability to tune aromatic and side chain properties via sulfur oxidation. These amino acids provide novel loci for peptide functionalization, with greater control of conformation possible than with other amino acids containing these functional groups.
C-Glycosyl amino acids through hydroboration-cross-coupling of exo-glycals and their application in automated solid-phase synthesis
Koch, Stefan,Schollmeyer, Dieter,L?we, Holger,Kunz, Horst
supporting information, p. 7020 - 7041 (2013/07/05)
O-Glycosylation is one of the most important post-translational modifications of proteins. The attachment of carbohydrates to the peptide backbone influences the conformation as well as the solubility of the conjugates and can even be essential for binding to specific ligands in cell-cell interactions or for active transport over membranes. This makes glycopeptides an interesting class of compounds for medical applications. To enhance the long-term availability of these molecules in vivo, the stabilization of the glycosidic bond between the amino acid residue and the carbohydrate is of interest. The described modular approach affords β-linked C-glycosyl amino acids by a sequence of Petasis olefination of glyconolactones, stereoselective hydroboration and a mild B-alkyl-Suzuki coupling reaction. The coupling products were transformed to C-glycosyl amino acid building-blocks suitable for solid-phase synthesis and successfully incorporated into a partial sequence of the tumor-associated MUC1-glycopeptide. The resulting C-glycopeptides are candidates for the development of long-term stable mimics of O-glycopeptide vaccines. Copyright
