123441-03-2Relevant articles and documents
Kinetic Modeling of the Blood Oxygenation Level Dependent (BOLD) Signals and Biocatalytic Reactions Observed in the Human Brain Using MRI: An Analysis of Normal and Pathological Conditions
Bykov, Valeriy I.,Semenova, Nataliya A.,Tsybenova, Svetlana B.,Varfolomeev, Sergey D.
, (2020)
A kinetic model describing the pulse of increased oxygen concentrations and the subsequent changes in the concentration of N-acetylaspartate in the excited nervous tissue of the human brain in response to an external signal is presented. The model is based on biochemical data, a multistage and nonlinear dynamic process the BOLD signal and N-acetylaspartate. The existence of multiple steady states explains the triggering effect of the system. The inhibitory effect of the substrate is a necessary factor for the autostabilization of N-acetylaspartate. The kinetic model allows the dynamic behavior of previously unmeasurable metabolites, namely, products of the hydrolysis of N-acetylaspartate, such as acetic and aspartic acid, and glutamic acid to be predicted. Kinetic modeling of the BOLD signal and the subsequent hydrolysis of N-acetylaspartate provides information about the biochemical and dynamic characteristics of some pathological conditions (schizophrenia, Canavan disease, and the superexcitation of the neural network).
Group-assisted Purification (GAP) Chemistry/Technology in synthesizing the chiral intermediate of rivastigmine and its ?-Alkyl benzylamine analogues
Yang, Bing,Zhang, Chun-Yan,Xu, Jing,Zheng, Da-Jun,Wang, Xiao-Ying,Dai, Hong,Shi, Yu-Jun,Zhu, Hai-Liang
, p. 1065 - 1068 (2019)
Introduction of (S)-configuration is the key step in the synthesis of the anti-dementia drug Rivastigmine. Twenty-one alkylation products were obtained through simple washing with hexane/ethyl acetate (v/v: 10/1) in good yields (>85%) and high diastereoselectivity (up to >99:1 dr). Moreover, the chiral auxiliary could be easily dissociated and readily regenerated. That is, the synthesis was proved to follow group-assisted purification (GAP) chemistry/technology. In addition, the chiral amine produced by this asymmetric alkylation reaction was effectively used in the synthesis of Rivastigmine.
Biaryl diphosphine ligands and their ruthenium complexes: Preparation and use for catalytic hydrogenation of ketones
Abdur-Rashid, Kamaluddin,Abdur-Rashid, Kareem,Dasgupta, Tara,Jia, Wenli,Lorraine, Shannen,Maragh, Paul
, (2020/07/10)
Procedures for the preparation of the nucleophilic diphosphine ligands (R)-(4,4′,6,6′-tetramethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine) ((R)-Ph-Garphos, 2a) and (S)-(4,4′,6,6′-tetramethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine) ((S)-Ph-Garphos, 2b) were described. The ligands were used to prepare the ruthenium(II) Ph-Garphos complexes, chloro(p-cymene)(R)-(4,4′,6,6′-tetraamethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine)ruthenium(II) chloride ([RuCl(p-cymene)(R)-Ph-Garphos]Cl (3)) and chloro(p-cymene)(S)-(4,4′,6,6′-tetraamethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine)ruthenium(II) chloride ([RuCl(p-cymene)(S)-Ph-Garphos]Cl (4)). In the presence of the chiral diamine co-ligands (1R,2R)-1,2-diphenylethane-1,2-diamine (R,R-DPEN) and (1S,2S)-1,2-diphenylethane-1,2-diamine (S,S-DPEN), complexes 3 and 4 were found to be catalyst precursors for the enantioselective reduction of aryl ketones under mild conditions (room temperature and 3–4 atm of H2). The chiral alcohols were isolated in moderate to good yields and with enantioselectivities of up to 93percent. The ruthenium complexes chloro(p-cymene)(R)-(4,4′,6,6′-tetramethoxybiphenyl-2,2′-diyl)bis(bis(3,5-dimethylphenyl)-phosphine)ruthenium(II) chloride ([RuCl(p-cymene)(R)-Xyl-Garphos]Cl (5)) and chloro(p-cymene)(S)-(4,4′,6,6′-tetramethoxybiphenyl-2,2′-diyl)bis(bis(3,5-dimethylphenyl)-phosphine)ruthenium(II) chloride ([RuCl(p-cymene)(S)-Xyl-Garphos]Cl (6)) were also prepared and used as catalyst precursors for the hydrogenation of aryl ketones in the presence of (R,R)-DPEN and (S,S)-DPEN. Significant improvements in the enantioselectivities of the alcohols (up to 98percent ee.) were afforded. A combination of 6 and (S,S)-DPEN afforded (R)-1-(3-methoxyphenyl)ethanol in 89percent yield and with 95percent ee which was shown to be a suitable precursor for the preparation of (S)-rivastigmine.