18633-25-5Relevant academic research and scientific papers
Proton Switch in the Secondary Coordination Sphere to Control Catalytic Events at the Metal Center: Biomimetic Oxo Transfer Chemistry of Nickel Amidate Complex
Kim, Soohyung,Jeong, Ha Young,Kim, Seonghan,Kim, Hongsik,Lee, Sojeong,Cho, Jaeheung,Kim, Cheal,Lee, Dongwhan
supporting information, p. 4700 - 4708 (2021/02/12)
High-valent metal-oxo species are key intermediates for the oxygen atom transfer step in the catalytic cycles of many metalloenzymes. While the redox-active metal centers of such enzymes are typically supported by anionic amino acid side chains or porphyrin rings, peptide backbones might function as strong electron-donating ligands to stabilize high oxidation states. To test the feasibility of this idea in synthetic settings, we have prepared a nickel(II) complex of new amido multidentate ligand. The mononuclear nickel complex of this N5 ligand catalyzes epoxidation reactions of a wide range of olefins by using mCPBA as a terminal oxidant. Notably, a remarkably high catalytic efficiency and selectivity were observed for terminal olefin substrates. We found that protonation of the secondary coordination sphere serves as the entry point to the catalytic cycle, in which high-valent nickel species is subsequently formed to carry out oxo-transfer reactions. A conceptually parallel process might allow metalloenzymes to control the catalytic cycle in the primary coordination sphere by using proton switch in the secondary coordination sphere.
Enantioselective organocatalysis-based synthesis of 3-hydroxy fatty acids and fatty γ-lactones
Bourboula, Asimina,Limnios, Dimitris,Kokotou, Maroula G.,Mountanea, Olga G.,Kokotos, George
, (2019/06/10)
3-Hydroxy fatty acids have attracted the interest of researchers, since some of them may interact with free fatty acid receptors more effectively than their non-hydroxylated counterparts and their determination in plasma provides diagnostic information regarding mitochondrial deficiency. We present here the development of a convenient and general methodology for the asymmetric synthesis of 3-hydroxy fatty acids. The enantioselective organocatalytic synthesis of terminal epoxides, starting from long chain aldehydes, is the key-step of our methodology, followed by ring opening with vinylmagnesium bromide. Ozonolysis and subsequent oxidation leads to the target products. MacMillan’s third generation imidazolidinone organocatalyst has been employed for the epoxide formation, ensuring products in high enantiomeric purity. Furthermore, a route for the incorporation of deuterium on the carbon atom carrying the hydroxy group was developed allowing the synthesis of deuterated derivatives, which may be useful in biological studies and in mass spectrometry studies. In addition, the synthesis of fatty γ-lactones, corresponding to 4-hydroxy fatty acids, was also explored.
Dinuclear Iron(III) and Nickel(II) Complexes Containing N-(2-Pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine: Catalytic Oxidation and Magnetic Properties
Jeong, Ah Rim,Shin, Jong Won,Jeong, Jong Hwa,Bok, Kwon Hee,Kim, Cheal,Jeong, Donghyun,Cho, Jaeheung,Hayami, Shinya,Min, Kil Sik
, p. 3023 - 3033 (2017/03/13)
Dinuclear FeIII and NiII complexes, [(phenO)Fe(N3)]2(NO3)2 (1) and [(phenOH)Ni(N3)2]2 (2), were prepared by treating Fe(NO3)3?9 H2O and Ni(NO3)2?6 H2O in methanol, respectively, with phenOH (=N-(2-pyridylmethyl)-N′-(2-hydroxyethyl)ethylenediamine) and NaN3; both 1 and 2 were characterized by elemental analysis, IR spectroscopy, X-ray diffraction, and magnetic susceptibility measurements. Two ethoxo-bridged FeIII and two azido-bridged NiII were observed in 1 and 2, respectively; corresponding antiferromagnetic interaction via the bridged ethoxo groups and strong ferromagnetic coupling via the bridged end-on azido ligands within the dimeric unit were observed. Complex 1 did not exhibit any catalytic activity, while 2 exhibited excellent catalytic activities for the epoxidation of aliphatic, aromatic, and terminal olefins.
Trinuclear nickel and cobalt complexes containing unsymmetrical tripodal tetradentate ligands: Syntheses, structural, magnetic, and catalytic properties
Shin, Jong Won,Jeong, Ah Rim,Lee, Sun Young,Kim, Cheal,Hayami, Shinya,Min, Kil Sik
, p. 14089 - 14100 (2016/11/06)
The coordination chemistries of the tetradentate N2O2-type ligands N-(2-pyridylmethyl)iminodiethanol (H2pmide) and N-(2-pyridylmethyl)iminodiisopropanol (H2pmidip) have been investigated with nickel(ii) and cobalt(ii/iii) ions. Three novel complexes prepared and characterized are [(Hpmide)2Ni3(CH3COO)4] (1), [(Hpmide)2Co3(CH3COO)4] (2), and [(pmidip)2Co3(CH3COO)4] (3). In 1 and 2, two terminal nickel(ii)/cobalt(ii) units are coordinated to one Hpmide- and two CH3CO2-. The terminal units are each connected to a central nickel(ii)/cobalt(ii) cation through one oxygen atom of Hpmide- and two oxygen atoms of acetate ions, giving rise to nickel(ii) and cobalt(ii) trinuclear complexes, respectively. Trinuclear complexes 1 and 2 are isomorphous. In 3, two terminal cobalt(iii) units are coordinated to pmidip2- and two CH3CO2-. The terminal units are each linked to a central cobalt(ii) cation through two oxygen atoms of pmidip2- and one oxygen atom of a bidentate acetate ion, resulting in a linear trinuclear mixed-valence cobalt complex. 1 shows a weak ferromagnetic interaction with the ethoxo and acetato groups between the nickel(ii) ions (g = 2.24, J = 2.35 cm-1). However, 2 indicates a weak antiferromagnetic coupling with the ethoxo and acetato groups between the cobalt(ii) ions (g = 2.37, J = -0.5 cm-1). Additionally, 3 behaves as a paramagnetic cobalt(ii) monomer, due to the diamagnetic cobalt(iii) ions in the terminal units (g = 2.53, =D= = 36.0 cm-1). No catalytic activity was observed in 1. However, 2 and 3 showed significant catalytic activities toward various olefins with modest to good yields. 3 was slightly less efficient toward olefin epoxidation reaction than 2. Also 2 was used for terminal olefin oxidation reaction and was oxidised to the corresponding epoxides in moderate yields (34-75%) with conversions ranging from 47-100%. The cobalt complexes 2 and 3 promoted the O-O bond cleavage to ～75% heterolysis and ～25% homolysis.
A discrete {Co4(μ3-OH)4}4+ cluster with an oxygen-rich coordination environment as a catalyst for the epoxidation of various olefins
Lee, Sun Young,Kim, Namseok,Lee, Myoung Mi,Jo, Young Dan,Bae, Jeong Mi,Hyun, Min Young,Yoon, Sungho,Kim, Cheal
, p. 1727 - 1736 (2016/01/30)
Using the sterically hindered terphenyl-based carboxylate, the tetrameric Co(ii) complex [Co4(μ3-OH)4(μ-O2CAr4F-Ph)2(μ-OTf)2(Py)4] (1) with an asymmetric cubane-type core has been synthesized and fully characterized by X-ray diffraction, UV-vis spectroscopy, and electron paramagnetic resonance spectroscopy. Interestingly, the cubane-type cobalt cluster 1 with 3-chloroperoxybenzoic acid as the oxidant was found to be very effective in the epoxidation of a variety of olefins, including terminal olefins which are more challenging targeting substrates. Moreover, this catalytic system showed a fast reaction rate and high epoxide yields under mild conditions. Based on product analysis and Hammett studies, the use of peroxyphenylacetic acid as a mechanistic probe, H218O-exchange experiments, and EPR studies, it has been proposed that multiple reactive cobalt-oxo species CoVO and CoIVO were involved in the olefin epoxidation.
Terminal and internal olefin epoxidation with cobalt(II) as the catalyst: Evidence for an active oxidant CoII-acylperoxo species
Hyun, Min Young,Kim, Soo Hyun,Song, Young Joo,Lee, Hong Gyu,Jo, Young Dan,Kim, Jin Hoon,Hwang, In Hong,Noh, Jin Young,Kang, Juhye,Kim, Cheal
, p. 7307 - 7312 (2012/11/07)
A simple catalytic system that uses commercially available cobalt(II) perchlorate as the catalyst and 3-chloroperoxybenzoic acid as the oxidant was found to be very effective in the epoxidation of a variety of olefins with high product selectivity under mild experimental conditions. More challenging targets such as terminal aliphatic olefins were also efficiently and selectively oxidized to the corresponding epoxides. This catalytic system features a nearly nonradical-type and highly stereospecific epoxidation of aliphatic olefin, fast conversion, and high yields. Olefin epoxidation by this catalytic system is proposed to involve a new reactive CoII-OOC(O)R species, based on evidence from H218O-exchange experiments, the use of peroxyphenylacetic acid as a mechanistic probe, reactivity and Hammett studies, EPR, and ESI-mass spectrometric investigation. However, the O-O bond of a CoII-acylperoxo intermediate (CoII-OOC(O)R) was found to be cleaved both heterolytically and homolytically if there is no substrate.
Termination of the structural confusion between plipastatin A1 and fengycin IX
Honma, Miho,Tanaka, Kazuaki,Konno, Katsuhiro,Tsuge, Kenji,Okuno, Toshikatsu,Hashimoto, Masaru
experimental part, p. 3793 - 3798 (2012/08/28)
Plipastatin A1 and fengycin IX were experimentally proven to be identical compounds, while these had been considered as diastereomers due to the permutation of the enantiomeric pair of Tyr in most papers. The 1H NMR spectrum changed to become quite similar to that of plipastatin A1, when the sample which provided resembled spectrum of fengycin IX was treated with KOAc followed by LH-20 gel filtration. Our structural investigations disclosed that the structures of these molecules should be settled into that of plipastatin A1 by Umezawa (l-Tyr4 and d-Tyr10).
Synthesis of aculeatins A and B via iterative hydrolytic kinetic resolution
Harbindu, Anand,Kumar, Pradeep
experimental part, p. 1479 - 1484 (2010/10/18)
A simple and concise approach for the synthesis of aculeatins A and B starting from (±)-epichlorohydrin is described. The synthetic strategy features Jacobsen's hydrolytic kinetic resolution and a Linchpin coupling as key steps. Georg Thieme Verlag Stuttgart.
Polyol synthesis with β-Oxyanionic alkyllithium Reagents: Syntheses of aculeatins A, B, and D
Malathong, Viengkham,Rychnovsky, Scott D.
scheme or table, p. 4220 - 4223 (2009/12/31)
Synthesis of ketone aldol products using a non-aldol route was developed. The β-phenylthio alcohols were prepared from optically pure oxiranes. Deprotonation and reductive lithiation generated the key intermediate, a β-oxyanionic alkyllithium reagent. Addition to a Weinreb amide produced the β-hydroxy ketone In >90% yield using only 1.5 equiv of the phenylthio alcohol. Stereoselective reduction of the ketone led to either the syn-or anti-1,3-diol. This simple, convergent sequence was used to prepare aculeatins A, B, and D from a common intermediate
Anticancer agents from the Australian tropical rainforest: Spiroacetals EBC-23, 24, 25, 72, 73, 75 and 76
Dong, Lin,Schill, Heiko,Grange, Rebecca L.,Porzelle, Achim,Johns, Jenny P.,Parsons, Peter G.,Gordon, Victoria A.,Reddell, Paul W.,Williams, Craig M.
experimental part, p. 11307 - 11318 (2010/05/02)
EBC-23, 24, 25, 72, 73, 75 and 76 were isolated from the fruit of Cinnamomum laubatii (family Lauraceae) in the Australian tropical rainforests. EBC-23 (1) was synthesized stereoselectively, in nine linear steps in 8% overall yield, to confirm the reported relative stereochemistry and determine the absolute stereochemistry. Key to the total synthesis was a series of Tietze - Smith linchpin reactions. The novel spiroacetal structural motif, exemplified by EBC-23 (1), was found to inhibit the growth of the androgen-independent prostate tumor cell line DU145 in the mouse model, indicating potential for the treatment of refractory solid tumors in adults.
