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Macrocyclic peptide-mimetic molecules are attracting renewed attention and have found widespread application in research fields ranging from biochemical science to materials science. Herein, we describe the synthesis and structural elucidation of cyclo[n]-p-arylopeptoids (classified into cyclic aromatic ε-amino acids) bearing various side chains, namely, C[n]pAP(Rn) (where n inside brackets denotes the number of main chain units and R inside parentheses represents side chains). We investigate the influence of n and R on the macrocyclization efficiency of linear p-arylopeptoid oligomers (n = 3, 4, 5) under high-dilution conditions with or without slow addition. The structures of the cyclo[4]-p-arylopeptoids (C[4]pAP(Rn)) and their conformational dynamics are disclosed on the basis of single-crystal X-ray analyses, viable-temperature (VT) 1H NMR studies, and density functional theory (DFT) calculations. We found two representative conformations (open and closed) of cyclo[4]-p-arylopeptoids (C[4]pAP(Rn)) in the solid state and whose preference in the solution state was most likely dependent on solvent polarity. We believe that this simple but dynamic macrocyclic peptide-mimetic molecular scaffold would be attractive for developing new functional molecular tools based on rational molecular design as well as molecular library screening strategies.

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Ti-6Al-4V alloy (Ti-Al-V) is used in dental implants and artificial hip joints to take advantage of its higher mechanical strength compared to cp Ti. However, the toxicity of vanadium and aluminum in the titanium alloy has been reported by several investigators since 1965. This study was carried out to compare the mechanical properties and the biocompatibility of Ti-Fe alloy (TiX®) to those of conventional metallic implant materials. The mechanical properties of TiX® were measured and compared with cp Ti, Ti-Al-V, SUS316, SUS304, Co-Cr-Mo, and Ag-Sn. The tensile strength of TiX® and Ti-Al-V were greater than those of Co-Cr-Mo, SUS316, and SUS304. The yield point of TiX® was slightly lower than that of Ti-Al-V, but higher than that of cp Ti. These results suggested the mechanical properties of TiX® were superior to those of Co-Cr-Mo, SUS316, and SUS304. To evaluate the biocompatibility, cell culture technique with L929 cells was used to investigate the cell multiplication, and SEM to investigate the morphological change of adhered cells onto TiX®. The cell growth rate of TiX® was slightly higher than those of Ti-Al-V and SUS316. Severe cytotoxicity was observed in Ag-Sn, and mild cytotoxicity in Ti-Al-V, SUS316, SUS304 using gyratory culture method. These results revealed that TiX® is a useful metallic material for wire, plate, porous, and mesh in dental and medical use, because of the favorable biocompatibility and easy fabrication.

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