Facile synthesis of L-kynurenine

Synthesis of l-Kynurenine and Homo-l-Kynurenine via an Aza-Fries Rearrangement

l-Kynurenine, a non-proteinogenic amino acid, is the primary metabolite of tryptophan via the kynurenine pathway. Kynurenine is involved in a variety of biological processes occurring in the human body, notably in the central nervous system. Thus, the study of this molecule offers multiple opportunities for drug discovery; however, an essential prelude for biological studies is to secure the supply of kynurenine and analogues thereof. A simple synthetic procedure for the efficient preparation of enantiomerically pure l-kynurenine from l-aspartic acid and its implementation to prepare homo-l-kynurenine from l-glutamic acid is presented. The approach relies on a photochemical aza-Fries rearrangement of the corresponding acyl-aniline as the fundamental transformation.

Stereoselective Assembly of Gigantic Chiral Molybdenum Blue Wheels Using Lanthanide Ions and Amino Acids

The synthesis of chiral polyoxometalates (POMs) is a challenge because of the difficulty to induce the formation of intrinsically chiral metal-oxo frameworks. Herein we report the stereoselective synthesis of a series of gigantic chiral Mo Blue (MB) POM clusters 1-5 that are formed by exploiting the synergy between coordinating lanthanides ions as symmetry breakers to produce MBs with chiral frameworks decorated with amino acids ligands; these promote the selective formation of enantiopure MBs. All the compounds share the same framework archetype, based on {Mo₁₂₄Ce₄}, which forms an intrinsically chiral Δ or Λ configurations, controlled by the configurations of functionalized chiral amino acids. The chirality and stability of 1-5 in solution are confirmed by circular dichroism, ¹H NMR, and electrospray ion mobility-mass spectrometry studies. In addition, the framework of the {Mo₁₂₄Ce₄} MB not only behaves as a host able to trap a chiral {Mo₈} cluster that is not accessible by traditional synthesis but also promotes the transformation of tryptophan to kynurenine in situ. This work demonstrates the potential and applicability of our synthetic strategy to produce gigantic chiral POM clusters capable of host-guest chemistry and selective synthetic transformations.

Synthesis of (±)-terpendole E

The first synthesis of the racemate of terpendole E, a specific inhibitor of the mitotic kinesin Eg5, has been achieved from a known tricyclic dihydroxy ketone by a 13-step sequence that involves diastereoselective installation of its C3 quaternary stereocenter via a cyclopropyl ketone intermediate and Pd-mediated two-step construction of the indole ring moiety as the key transformations.

Near-infrared photochromic behavior in a donor-acceptor type diarylethene modulated by the cyanide anion

Two new near-infrared (NIR) photochromic compounds, containing both electron-donating (D) and accepting groups (A), have been developed and their NIR photochromic and fluorescence performances can be modulated by the cyanide anion. Such a colorimetric cyanide sensor has been achieved based on this donor-photochromic bridge-acceptor system.

TD-DFT investigation of diarylethene dyes with cyclopentene, dihydrothiophene, and dihydropyrrole bridges

We have investigated the visible spectra of closed-ring diarylethenes presenting cyclopentene, dihydrothiophene, and dihydropyrrole bridging structures. Our simulations have been performed with an ab initio time-dependent density functional theory approach that takes into account bulk environmental effects. The computed lambda(max) agree qualitatively with experiment, and once a simple statistical treatment is performed, a quantitative agreement is reached. Indeed, after linear fitting correction, the mean absolute error is limited to 6 nm or 0.03 eV for the 57 diarylethenes considered. To unravel the most important parameters for this photochromic class, several structural parameters are correlated to the UV/vis spectra. It turns out that the bond length alternation in the chromogenic unit allows a fast and accurate prediction of the color of these dyes. In addition, we compare our results to available electrochemical data.

Synthesis of C-nucleosides designed to participate in triplex formation with native DNA: specific recognition of an A:T base pair in DNA

[structure: see text] We have previously described a system of 2-aminoquinoline- and 2-aminoquinazoline-based C-deoxynucleosides (TRIPsides) that are designed to be incorporated into oligomers that can specifically bind in the major groove via Hoogsteen base pairing to any sequence of native DNA. The four TRIPsides are termed antiGC, antiCG, antiTA, and antiAT with respect to the Watson-Crick base pair targets that they bind. The first three TRIPsides have been prepared, characterized, and shown to form stable and sequence-specific triplexes. In the present study, we describe the preparation of two molecules, 2-amino-4-(2'-deoxy-beta-D-ribofuranosyl)quinazoline (7) and 2-amino-6-fluoro-4-(2'-deoxy-beta-D-ribofuranosyl)quinoline (14), that can serve as the remaining antiAT TRIPside. The phosphoramidites of 7 and 14 were prepared, but only the latter was successfully incorporated into DNA oligomers. It is demonstrated using UV-visible melting experiments that 14 forms sequence-specific intramolecular triplets with A:T base pairs at physiological pH.

Diastereoselective Photochromism of Bisbenzothienylethenes with an Oxycarbonyl-Related Functional Group on the Side Chain

Nine 1-[2-(1-substituted)ethyl-3-benzothienyl]-2-(2-methyl-3-benzothienyl)hexafluorocyclopentenes (4-substituted benzoyloxy, N-arylcarbamoyloxy, and aryloxycarbonyloxy) were synthesized. They showed diastereoselective photochromic ring closure upon UV irradiation. Among them, 4-nitrophenoxycarbonyloxy-substituted compound recorded a remarkable 94% diastereomer excess with 91% conversion to the closed form.

Photochromic and Luminescence Switching Properties of a Versatile Diarylethene-Containing 1,10-Phenanthroline Ligand and Its Rhenium(I) Complex

A versatile bis(2,5-dimethyl-3-thienyl)-1,10-phenanthroline photochromic ligand has been successfully synthesized via a Suzuki cross-coupling reaction. The excitation wavelength for photochromic reaction of the dithienylphenanthroline could be extended from lambda </= 340 nm in the UV region to ca. 480 nm in the visible region, corresponding to the MLCT excitation, through the incorporation into the rhenium(I) tricarbonyl system. Reversible switching of the emissive state by the photochromic reaction has also been demonstrated.

Synthesis and biochemical evaluation of N-(4-phenylthiazol-2-yl)benzenesulfonamides as high-affinity inhibitors of kynurenine 3-hydroxylase

In this paper we describe the synthesis, structure-activity relationship (SAR), and biochemical characterization of N-(4-phenylthiazol-2-yl)benzenesulfonamides as inhibitors of kynurenine 3-hydroxylase. The compounds 3,4-dimethoxy-N-[4-(3-nitrophenyl)thiazol-2-yl]benzenesulfonamide 16 (IC50 = 37 nM, Ro-61-8048) and 4-amino-N-[4-[2-fluoro-5-(trifluoromethyl)phenyl]-thiazol-2-yl] benzenesulfonamide 20 (IC50 = 19 nM) were found to be high-affinity inhibitors of this enzyme in vitro. In addition, both compounds blocked rat and gerbil kynurenine 3-hydroxylase after oral administration, with ED50's in the 3-5 mumol/kg range in gerbil brain. In a microdialysis experiment in rats, 16 dose dependently increased kynurenic acid concentration in the extracellular hippocampal fluid. A dose of 100 mumol/kg po led to a 7.5-fold increase in kynurenic acid outflow. These new compounds should allow detailed investigation of the pathophysiological role of the kynurenine pathway after neuronal injury.

Germanium and Silicon Linking Strategies for Traceless Solid-Phase Synthesis

Here we describe the development and application of germanium and silicon linkage strategies for the solid-phase synthesis of aromatic compounds, as demonstrated for 1,4-benzodiazepine derivatives. The metal-aryl bond that attaches the benzodiazepine to the polymeric support may be cleaved by electrophilic reagents such as H(+) and Br(2) to provide the corresponding substituted derivatives. A number of compounds have been prepared in good overall yield for the eight- or nine-step process. This approach can also be applied to the solid-phase synthesis of libraries of other classes of aromatic compounds.