Zinc complexes supported by (benzimidazolyl)pyridine alcohol ligands as highly efficient initiators for ring-opening polymerization of ε-caprolactone

Efficient Entropy-Driven Inhibition of Dipeptidyl Peptidase III by Hydroxyethylene Transition-State Peptidomimetics

Dipeptidyl peptidase III (DPP3) is a ubiquitously expressed Zn‐dependent protease, which plays an important role in regulating endogenous peptide hormones, such as enkephalins or angiotensins. In previous biophysical studies, it could be shown that substrate binding is driven by a large entropic contribution due to the release of water molecules from the closing binding cleft. Here, the design, synthesis and biophysical characterization of peptidomimetic inhibitors is reported, using for the first time an hydroxyethylene transition‐state mimetic for a metalloprotease. Efficient routes for the synthesis of both stereoisomers of the pseudopeptide core were developed, which allowed the synthesis of peptidomimetic inhibitors mimicking the VVYPW‐motif of tynorphin. The best inhibitors inhibit DPP3 in the low μM range. Biophysical characterization by means of ITC measurement and X‐ray crystallography confirm the unusual entropy‐driven mode of binding. Stability assays demonstrated the desired stability of these inhibitors, which efficiently inhibited DPP3 in mouse brain homogenate.

Ring opening polymerization of ε-caprolactone initiated by titanium and vanadium complexes of ONO-type schiff base ligand

A phenoxy-imine proligand with the additional OH donor group, 4,6-tBu2-2-(2-CH2(OH)-C6H4N = CH)C6H3OH (LH2), was synthesized and used to prepare group 4 and 5 complexes by reacting with Ti(OiPr)4 (LTi) and VO(OiPr)3 (LV). All new compounds were characterized by the FTIR, 1H and 13C NMR spectroscopy and LTi by the single-crystal X-ray diffraction analysis. The complexes were used as catalysts in the ring opening polymerization of ε-caprolactone. The influence of monomer/transition metal molar ratio, reaction time, polymerization temperature as well as complex type was investigated in detail. The complexes showed high (LTi) and moderate (LV) activity in ε-caprolactone polymerization and the resultant polycaprolactones exhibited Mn and Mw/Mn values ranging from 4.0 · 103 to 18.7 · 103 g/mol and from 1.4 to 2.5, respectively.

Fast and controlled ring-opening polymerization of δ-valerolactone catalyzed by benzoheterocyclic urea/MTBD catalysts

New benzoheterocyclic urea/MTBD catalysts are highly efficient and controllable in the ring-opening polymerization of δ-valerolactone under solvent-free conditions or in solution.

Polymers of ε-Caprolactone Using New Copper(II) and Zinc(II) Complexes as Initiators: Synthesis, Characterization and X-Ray Crystal Structures

Five of six new Zn(II) and Cu(II) complexes were active in the ring-opening polymerization (ROP) of ε-caprolactone (CL) under solvent-free conditions, producing polycaprolactones (PCLs) of high crystallinity with molecular weights between 22,900 and 38,700 g mol⁻¹ and decomposition temperatures above 260 °C. ¹H NMR analysis demonstrated that the PCLs obtained were mainly linear, having hydroxymethylene groups at the chain ends. The results obtained indicated a significant improvement in terms of the ratio of monomer:initiator compared to related Cu(II) and Zn(II) complexes. In addition, the structures of the complexes 1 and 4 were determined by single-crystal X-ray diffraction. The synthesis and full characterization of all complexes are described in this paper.

Poly(delta-gluconolactone) and Poly(delta-gluconolactone-ε-caprolactone) from delta-Gluconolactone and ε-Caprolactone by Ring-Opening Polymerization

Poly(delta-gluconolactone) (PGL) and poly(delta-gluconolactone-ε-caprolactone) (P(GL-CL)) were synthesized through ring-opening polymerization (ROP) and characterized by FT-IR, NMR, XRD, intrinsic viscosity, GPC, DSC, and TGA. The crystallinity of P(GL-CL) with various d-GL/CL ratios (d-GL/CL = 5 : 5, 4 : 6, 3 : 7, 2 : 8, and 1 : 9) was 12.09 to 59.78% while PGL was amorphous. Melting temperature (Tm) of these polymers was 49.8 to 62.0°C and decomposition temperature was 282 to 489°C depending on the d-GL/CL ratios. In addition, all these polymers were degradable and the degradation rates could be controlled by adjusting d-GL/CL ratios. These results indicated that PGL and P(GL-CL) might be promising novel absorbable materials.

Living ring-opening polymerization of ε-caprolactone catalyzed by β-quinolyl-enamino aluminium complexes: ligand electronic effects

Seven aluminium β-quinolyl-enaminates with varying substituents have been synthesized and applied to the ROP of ε-CL. A comparative study on catalytic activities and reaction kinetics was conducted.

Coordination Polymers Containing 1,3-Phenylenebis-((1H-1,2,4-triazol-1-yl)methanone) Ligand: Synthesis and ε-Caprolactone Polymerization Behavior

The reaction of isophthaloyl dichloride with 1H-1,2,4-triazole afforded the new ligand 1,3-phenylenebis(1,2,4-triazole-1-yl)methanone (1). A series of Co(II), Cu(II), Zn(II) and Ni(II) complexes were synthesized using 1 and then characterized by melting point analysis, elemental analysis, theoretical calculations, thermogravimetric analysis, X-ray powder diffraction, nuclear magnetic resonance, infrared and Raman spectroscopy. Experimental and computational studies predict the formation of coordination polymers (CPs). The cobalt and copper CPs and zinc(II) complex were found to be good initiators for the ring-opening polymerization of ε-caprolactone (CL) under solvent-free conditions. ¹H-NMR analysis showed that the obtained polymers of CL were mainly linear and had terminal hydroxymethylene groups. Differential scanning calorimetry showed that the obtained polycaprolactones had high crystallinity, and TGA showed that they had decomposition temperatures above 400 °C. These results provide insight and guidance for the design of metal complexes with potential applications in the polymerization of CL.