17302-46-4Relevant articles and documents
Stereoisomers and functional groups in oxidorhenium(v) complexes: Effects on catalytic activity
Schachner,Berner,Belaj,M?sch-Zanetti
, p. 8106 - 8115 (2019)
The syntheses of oxidorhenium(v) complexes [ReOCl(L1a-c)2] (3a-c), equipped with the bidentate, mono-anionic phenol-dimethyloxazoline ligands HL1a-c are described. Ligands HL1b-c contain functional groups on the phenol ring, compared to parent ligand 2-(4,4-dimethyl-4,5-dihydro-1,3-oxazol-2-yl)-phenol H1a; namely a methoxy group ortho to the hydroxyl position (2-(4,4-dimethyl-4,5-dihydro-1,3-oxazol-2-yl)-6-methoxyphenol, H1b), or a nitro group para to the hydroxyl position (2-(4,4-dimethyl-4,5-dihydro-1,3-oxazol-2-yl)-4-nitrophenol, H1c). Furthermore, oxidorhenate(v) complexes (NBu4)[ReOCl3(L1a-b)] (2a-b) were synthesized for solid state structural comparisons to 3a-b. All novel complexes are fully characterized including NMR, IR and UV-Vis spectroscopy, MS spectrometry, X-ray crystallography, elemental analysis as well as cyclic voltammetry. The influence of functional groups (R = -H, -OMe and -NO2) on the catalytic activity of 3a-c was investigated in two benchmark catalytic reactions, namely cyclooctene epoxidation and perchlorate reduction. In addition, the previously described oxidorhenium(v) complex [ReOCl(oz)2] (4), employing the phenol-oxazoline ligand 2-(4,5-dihydro-2-oxazolyl)phenol Hoz, was included in these catalysis studies. Complex 4 is a rare case in oxidorhenium(v) chemistry where two stereoisomers could be separated and fully characterized. With respect to the position of the oxazoline nitrogen atoms on the rhenium atom, these two stereoisomers are referred to as N,N-cis and N,N-trans isomer. A potential correlation between spectroscopic and structural data to catalytic activity was evaluated.
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Barany,Pianka
, p. 965 (1946)
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Reliable folding of hybrid tetrapeptides into short β-hairpins
Sun, Xue-Yi,Zhong, Yulong,Li, Yao-Hua,Miller, Daniel P.,Buttan, Sagar,Wu, Xiang-Xiang,Zhang, Yukun,Tang, Quan,Tan, Hong-Wei,Zhu, Jin,Liu, Rui,Zurek, Eva,Lu, Zhong-Lin,Gong, Bing
supporting information, p. 257 - 261 (2021/07/10)
Five hybrid tetrapeptides, each consisting a central dipeptide segment of α-amino acid residues flanked by two aromatic γ-amino acid residues, are found to fold into well-defined β-hairpin conformations as shown by NMR, computational study, and X-ray structures. The turn loop of this β-hairpin motif accommodates different two-residue α-amino acid sequences from the highly flexible Gly-Gly, to the more restricted D-Pro-Gly. The presence of α-amino acid side chains enhances the stabilities of the β-hairpins with the exception of D-Pro-Gly-which results in destabilization. Based on this hairpin/turn motif, a variety of different dipeptide sequences of α-amino acids which rarely occur in β-turns can be introduced and presented as two-residue loops.
Calcium Coordination Solids for pH-Triggered Release of Olsalazine
Levine, Dana J.,Gonzalez, Miguel I.,Legendre, Christina M.,Run?evski, Tom?e,Oktawiec, Julia,Colwell, Kristen A.,Long, Jeffrey R.
, p. 1739 - 1742 (2017/11/15)
Calcium coordination solids were synthesized and evaluated for delivery of olsalazine (H4olz), an anti-inflammatory compound used for treatment of ulcerative colitis. The materials include one-dimensional Ca(H2olz)?4 H2O chains, two-dimensional Ca(H2olz)?2 H2O sheets, and a three-dimensional metal-organic framework Ca(H2olz)?2DMF (DMF=N,N-dimethylformamide). The framework undergoes structural changes in response to solvent, forming a dense Ca(H2olz) phase when exposed to aqueous HCl. The compounds Ca(H2olz)?x H2O (x=0, 2, 4) were each pressed into pellets and exposed to simulated gastrointestinal fluids to mimic the passage of a pill from the acidic stomach to the pH-neutral intestines. All three calcium materials exhibited a delayed release of olsalazine relative to Na2(H2olz), the commercial formulation, illustrating how formulation of a drug within an extended coordination solid can serve to tune its solubility and performance.
