Catalytic Chemoselective O-Phosphorylation of Alcohols

Phosphorylation of alcohols is a fundamentally important reaction in both life science and physical science. Product phosphate monoesters play key roles in living organisms, natural products, pharmaceuticals, and organic materials. Most of the chemical methods to date for synthesizing phosphate monoesters, however, require multistep sequences or are limited to specific types of substrates possibly due to harsh conditions. An alternative way to enable the simple production of phosphate monoesters from highly functionalized precursor alcohols is, thus, highly desired. We report herein a catalytic phosphorylation of alcohols with high functional group tolerance using tetrabutylammonium hydrogen sulfate (TBAHS) and phosphoenolpyruvic acid monopotassium salt (PEP-K) as the catalyst and phosphoryl donor, respectively. This method enables the direct introduction of a nonprotected phosphate group to the hydroxy group of a diverse menu of alcohol substrates, including functionalized small molecules, carbohydrates, and unprotected peptides. Nuclear magnetic resonance, mass spectrometric, and density functional theory analyses suggest that an unprecedented mixed anhydride species, generated from PEP-K and TBAHS, acts as an active phosphoryl donor in this reaction. This operationally simple and chemoselective catalytic phosphorylation allows for the efficient production of densely functionalized O-phosphorylated compounds, which are useful in diverse fields including biology and medicine.

Design, Synthesis, and Properties of a Chemically Tethered Amyloid-β Segment Trimer Resistant to Intertrimer Mis-aggregation

The oligomer species of amyloid-β peptide (Aβ) may be relevant to the development of Alzheimer's disease. Isolating specific oligomer species of Aβ (i.e., dimers, trimers, tetramers, etc.), however, is difficult due to the transient, labile property of the oligomers. Here, we improved the resistance to intertrimer mis-aggregation of chemically tethered Aβ_25-35 trimers by introducing charged structures to the cyclic peptide tether that is covalently attached to the Aβ chain. The resistance to aggregation of the chemically tethered trimers positively correlated with the number of negative charges at the tether. Thus, a chemical trimer possessing three malonic acids at the tether exhibited high resistance because of the attenuated self-association by anionic repulsion. In addition, the malonic acid trimer possessed amyloidogenic properties such as cross-β-sheet structures, seeding activity, and cytotoxicity. This is the first study demonstrating that chemical modifications at the non-Aβ component enhance the resistance to aggregation of chemically tethered Aβ oligomers, by which the structural integrity of Aβ is maintained. Biological/biophysical evaluations of the intertrimer aggregation-resistant trimer may offer new, useful insights into the pathological functions of Aβ oligomers.

Induction of ADCC by a folic acid–mAb conjugate prepared by tryptophan-selective reaction toward folate-receptor-positive cancer cells

We developed conjugates between monoclonal antibody (mAb) and folic acid (FA) by using a tryptophan (Trp)-selective reaction, which yields relatively homogenous products compared to conventional methods. The obtained mAb–FA conjugates showed significant cellular cytotoxicity toward folate receptor-expressing cancer cells, demonstrating that the conjugates retained the Fc region's original function.

mAb–folic acid conjugates were prepared by a tryptophan-selective reaction using an organic radical under ambient conditions, which showed significant induction ability of antibody-dependent cellular cytotoxicity.

P2696Clinical characteristics of late catch-up phenomenon after implantation of 2nd generation drug eluting stent

Introduction

Late catch-up phenomenon (LCU) of 1st generation drug eluting stent (DES) has been increasing yearly despite the rate of restenosis in 1 year has reduced compared with bare metal stent (BMS). 2nd generation DES was more improved than 1st generation DES and suggested more benefits about clinical outcome.

Purpose

To investigate the incidence and predictor of LCU after implantation of 2nd generation DES and to evaluate the association between LCU phenomenon and adverse events.

Methods

Between August 2012 and July 2013, a total of 1665 consecutive patients (1956 lesions with elective/urgent PCI) were enrolled in SHINANO 5 years Registry (a prospective observational multicenter cohort study) from 13 institutions in Nagano, Japan. 711 patients that were treated with 2nd generation DES and 576 patients with BMS were selected. Exclusion criterias were cases of 1st DES, only POBA, only aspiration and chronic total occulusion.

Results

There were significant difference about patients background between BMS and 2nd generation DES groups. Those groups were matched with propensity score. After matching, 822 patients (BMS group 411 patients, 2nd generation group 411 patients) were analyzed. The rates of 2nd DES and BMS restenosis 5 years after initial PCI were 9.2% and 8.5% (p=0.572), those of LCU were 2.6% and 5.6% (p=0.043) by 1 year landmark analysis. Cox proportional hazards analysis revealed that the DES in-stent restenosis (ISR) lesion and higher HbA1c were independent predictors for LCU from 1year to 5year (HR 5.304, p=0.009, HR 1.254, p=0.015), but 2nd generation DES was not. Kaplan Meier curve showed no association between LCU phenomenon and all cause death (p=0.446). Cox regression analysis showed LCU was not independent predictor for all cause death (p=0.414).

Conclusions

Implantation to DES-ISR lesion with 2nd generation DES was associated with higher LCU. Despite of more complex lesions with 2nd generation DES, there were no differences of LCU incidence between 2nd generation DES and BMS.

Acknowledgement/Funding

None

Amine-tethered phenylboronic acid-enabling ring-opening strategy for carbon chain elongation from double aldol cyclic hemiacetals

The addition of carbon nucleophiles to cyclic hemiacetal forms of double aldols is a promising approach toward the synthesis of structurally attractive 1,3-polyol derivatives. Cyclic hemiacetals are generally unreactive to carbon nucleophiles under neutral conditions, however, because the electrophilic aldehyde function is masked. Here we developed an amine-tethered phenylboronic acid 7g, which transforms double aldol cyclic hemiacetals to ring-opened linear aldehydes. Combined with the previously-developed copper-catalysed asymmetric double aldol reaction (L. Lin, K. Yamamoto, H. Mitsunuma, Y. Kanzaki, S. Matsunaga and M. Kanai, J. Am. Chem. Soc., 2015, 137, 15418), this method produced synthetically useful chiral building blocks containing a 1,3-di- or tri-ol moiety.

Photophysical properties and application in live cell imaging of B,B-fluoro-perfluoroalkyl BODIPYs

The photophysical properties of newly identified B,B-fluoro-perfluoroalkyl BODIPYs (2 and 3), which possess a fluoro group and a trifluoromethyl or pentafluoroethyl group at the boron center, were investigated. B,B-Fluoro-perfluoroalkyl BODIPYs 2 and 3 exhibited better photophysical/chemical properties than B,B-difluoro-BODIPY 1, as follows: (1) higher photostability both in methanol solvent and in a live cell environment, (2) higher stability against acid degradation, and (3) improved fluorescence signal-to-noise ratios in a cell system. These favorable properties of B,B-fluoro-perfluoroalkyl BODIPYs are likely due to the highly electron-withdrawing nature of the perfluoroalkyl groups on the boron atom, which reduces the reactivity to 1O2 and strengthens the complexation of the dipyrromethene ligands to the boron atom. Thus, B,B-fluoro perfluoroalkyl BODIPYs may be useful functional molecules for various applications.

Site-Selective Synthetic Acylation of a Target Protein in Living Cells Promoted by a Chemical Catalyst/Donor System

Cell biology is tightly regulated by post-translational modifications of proteins. Methods to modulate post-translational modifications in living cells without relying on enzymes or genetic manipulation are, however, largely underexplored. We previously reported that a chemical catalyst (DSH) conjugated with a nucleosome-binding ligand can activate an acyl-CoA and promote site-selective lysine acylation of histones in test tubes. In-cell acylation by this catalyst system is challenging, however, mainly due to the low cell permeability of acyl-CoA and the propensity of DSH to form inactive disulfide. Here, we report a new catalyst system effective for in-cell acylation, comprising a cell-permeable acyl donor and pro-drugged DSH. Using E. coli dihydrofolate reductase and trimethoprim as a model protein and ligand pair, the catalyst system enabled site-selective acylation of the target protein in living cells. The findings will lead to the development of useful chemical biology tools and new therapeutic strategies capable of synthetically modulating post-translational modifications.

Catalytic asymmetric allylation of aldehydes with alkenes through allylic C(sp3)-H functionalization mediated by organophotoredox and chiral chromium hybrid catalysis

We describe a hybrid system that realizes cooperativity between an organophotoredox acridinium catalyst and a chiral chromium complex catalyst, thereby enabling unprecedented exploitation of unactivated hydrocarbon alkenes as precursors to chiral allylchromium nucleophiles for asymmetric allylation of aldehydes. The reaction proceeds under visible light irradiation at room temperature, affording the corresponding homoallylic alcohols with a diastereomeric ratio >20/1 and up to 99% ee. The addition of Mg(ClO4)2 markedly enhanced both the reactivity and enantioselectivity.

Photo-oxygenation inhibits tau amyloid formation

Amyloid-selective catalytic photo-oxygenation of the tau protein is a possible therapeutic strategy for Alzheimer's disease, via the inhibition of tau fibril formation.