Refernces
10.1002/chem.201103411
The study focuses on the synthesis and investigation of bifunctional azo derivatives that combine push–pull fluorophores and azo photochromes to create fluorescent structures in thin films upon light-induced migration. The researchers systematically explored the photochromic and emissive properties of these bifunctional molecules and compared them to those of corresponding model compounds. They determined fluorescence lifetimes and photoisomerization and fluorescence quantum yields in toluene solution. The study utilized femtosecond transient absorption spectra to reveal that the fluorophores evolve into a distorted intramolecular charge transfer excited state, competing with energy transfer to the azo moiety. A significant finding was the effectiveness of a 10 ? long rigid and nonconjugated bridge between the photoactive units, which inhibits energy transfer and enhances free volume, favoring photoactivated molecular migration in the solid state. The research provides insights into the design of fluorescent photoswitchable molecules for tracking photomechanically-activated single systems and offers new avenues for the development of azo bulk photomigration.
10.1021/jo015703t
The research focuses on the synthesis of the cyclic heptapeptide Trunkamide A, a biologically active compound derived from marine organisms, specifically the colonial ascidian Lissoclinum sp. The study outlines a solid-phase approach for the total synthesis of Trunkamide A, which includes the use of a quasi-orthogonal protecting scheme with tert-butyl and fluorenyl-based groups on a chlorotrityl resin, HOAt-based coupling reagents, and cyclizations in solution. Key reactants in the synthesis process include Fmoc-protected amino acids, DIPCDI, HOBt, and DAST, among others. The synthesis involves several steps such as the preparation of reverse prenyl derivatives of Ser and Thr, introduction of a protected amino thionoacid derivative, and formation of the thiazoline ring with DAST. The synthesized product was analyzed using techniques like HPLC, ES-MS, HRMS, and NMR spectroscopy to confirm its structure and purity. The research also discusses the challenges and optimizations in the synthesis process, making it suitable for large-scale synthesis of Trunkamide A and related peptides.
10.1016/j.tetlet.2003.11.133
The study presents a concise synthesis method for a novel class of homochiral aromatic amino acid surrogates, featuring tetrahydroindazole or benzisoxazole systems. These surrogates were synthesized through the acylation of cyclic 1,3-diketone by the side-chain carboxyl functionality of specific amino acid precursors, followed by a regioselective condensation with hydrazine, N-benzylhydrazine, and hydroxylamine. The synthetic strategy is versatile, allowing for the creation of structurally diverse derivatives. These novel amino acids can be efficiently incorporated into proteins and have potential applications in imparting unique properties to biological peptides. The study also includes the synthesis of Na-Fmoc-protected derivatives, which are useful for solid-phase peptide assembly, and the exploration of the stereochemistry integrity of the homochiral starting material through chemical transformations. The synthesized amino acids offer opportunities as structural surrogates of tryptophan and as building blocks for designing molecular probes.
10.1016/j.tetlet.2007.11.004
The research focuses on the development of a microwave-assisted method for the solid phase synthesis of pseudopeptides containing ester bonds, aiming to reduce reaction times and improve yields. The study utilized a pseudodipeptide (Fmoc-LysW[COO]Leu-NH2) as a model system and optimized the microwave-assisted esterification reaction using Fmoc chemistry. The experiments involved various reaction times, temperatures, and solvents, with 1,3-diisopropylcarbodiimide (DIC) as the coupling reagent. The synthesized pseudopeptides were analyzed for purity and yield, which were found to be superior when using the microwave irradiation method compared to conventional methods. The analyses included Fmoc quantitation assay, ninhydrin test, C18 reverse phase HPLC, and ESI mass spectrometry to confirm the structure and purity of the synthesized pseudopeptides.
