Children learn through play, and they learn more than adults might expect. Science experiments are a great way to spark their curiosity, get their minds active, and encourage them to do something that doesn¡¯t involve a screen. 246047-72-3, C46H65Cl2N2PRu. A document type is Article, introducing its new discovery., Application In Synthesis of (1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene)dichloro(phenylmethylene)(tricyclohexylphosphine)ruthenium
Synthesis and high-resolution NMR structure of a beta3- octapeptide with and without a tether introduced by olefin metathesis
Bridging between (i)- and (i+3)-positions in a beta3-peptide with a tether of appropriate length is expected to prevent the corresponding 314-helix from unfolding (Fig. 1). The beta3-peptide H-beta3hVal-beta3hLys-beta3hSer(All) -beta3hPhe-beta3hGlu-beta3hSer(All) -beta3hTyr-beta3hIle-OH (1; with allylated betahSer residues in 3-and 6-position), and three tethered beta-peptides 2 – 4 (related to 1 through ring-closing metathesis) have been synthesized (solid-phase coupling, Fmoc strategy, on chlorotrityl resin; Scheme). A comparative CD analysis of the tethered beta-peptide 4 and its non-tethered analogue 1 suggests that helical propensity is significantly enhanced (threefold CD intensity) by a (CH2)4 linker between the beta3hSer side chains (Fig. 2). This conclusion is based on the premise that the intensity of the negative Cotton effect near 215 nm in the CD spectra of beta3-peptides represents a measure of ‘helical content’. An NMR analysis in CD3OH of the two beta3- octapeptide derivatives without (i.e., 1) and with tether (i.e., 4; Tables 1 – 6, and Figs. 4 and 5) provided structures of a degree of precision (by including the complete set of side chainside chain and side chain – backbone NOEs) which is unrivaled in beta-peptide NMR-solution-structure determination. Comparison of the two structures (Fig. 5) reveals small differences in side-chain arrangements (separate bundles of the ten lowest-energy structures of 1 and 4, Fig. 5, A and B) with little deviation between the two backbones (superposition of all structures of 1 and 4, Fig. 5, C). Thus, the incorporation of a CH 2-O-(CH2)4-O-CH2 linker between the backbone of the beta3-amino acids in 3-and 6-position (as in 4) does accurately constrain the peptide into a 314-helix. The NMR analysis, however, does not suggest an increase in the population of a 3 14-helical backbone conformation by this linkage. Possible reasons for the discrepancy between the conclusion from the CD spectra and from the NMR analysis are discussed.
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Highly efficient and robust molecular ruthenium catalysts for water oxidation,
Catalysts | Special Issue : Ruthenium Catalysts – MDPI