Atropisomeric Flavoenzyme Models with a Modified Pyrimidine Ring: Syntheses, Physical Properties, and Stereochemistry in the Reactions with NAD(P)H Analogs
摘要:
Optically active 5-deazaflavin derivatives (3-aryl-10-(4-tert-butylphenyl)pyrimido[4,5-b]quinoline-2,4(3H,10H)-dione) with an axial chirality at the pyrimidine ring have been synthesized, and the kinetics of enantiomerization have been measured for some of them. The absolute configurations of these compounds have been determined by X-ray crystallographic analysis and chemical reactions for the first time in atropisomeric flavoenzyme models. Enantioface-differentiating (net) hydride-transfer reactions with 1-benzyl-1,4-dihydronicotinamide (BNAH) have revealed that the selectivity of the reacting face. of the 3-[2-(hydroxymethyl)phenyl] derivative 1 changes depending on the presence or absence of Mg2+; the hydroxymethyl group of 1 exerts steric inhibition in the absence of Mg2+, whereas it facilitates the approach of BNAH. in the presence of Mg2+ Asymmetric (net) hydride-transfer reactions with chiral 1,4-dihydro-2,4-dimethyl-N-(alpha-methylbenzyl)-1-propylnicotinamide (Me(2)PNPH) predict that the most favorable intermolecular arrangement of these two molecules at the transition state is the one in which the pyrimidine ring of 1 and the carbamoyl group of Me(2)PNPH tend to face each other and the maximum overlap of their molecular planes is achieved regardless of the presence or absence of Mg2+. The arrangement mimics that of FAD and NADPH in the active site of a flavoenzyme. The present result indicates an energetically favorable overlap of the molecular planes of a flavin and an NAD(P)H coenzyme, as well. as a significant influence of functional groups from an apoenzyme in proximity to a flavin coenzyme on the stereochemistry of biological redox reactions.
可以说,水是还原反应的理想氢源,但在实践中存在很大困难。在这项工作中,利用水作为氢源,在完整的电池中通过直流电或快速交变极性电流电解来电化学还原苯甲酸酯,具体取决于酯的电子特性。值得注意的是,使用 D 2 O 的反应提供了有价值的d 2 -苯甲醇,D 结合率高达 97%。机理研究表明,反应途径取决于底物。
α,α-Dideuterio benzyl alcohols are importantbuildingblocks for the synthesis of deuterium-labeled medicines and agrochemicals. We have developed the first general single-electron transfer reductive deuteration of readily commercially available aromatic esters for the synthesis of α,α-dideuterio benzyl alcohols using benign D2O and a mild single-electron donor SmI2. This operationally convenient method
Supersonic jet studies of benzyl alcohols: minimum energy conformations and torsional motion
作者:Hoong Sun Im、E. R. Bernstein、Henry V. Secor、Jeffrey I. Seeman
DOI:10.1021/ja00012a008
日期:1991.6
Supersonic jet mass resolved excitation spectroscopy is employed to determine the minimum energy conformations of benzyl alcohol and a series of nine methyl-, ethyl-, fluoro-, and aminobenzyl alcohols. The interpretation of the time-of-flight mass spectra (TOFMS) of these molecules leads to the assignment of specific molecular geometries for each system. The minimum energy conformation of the -CH2O moiety
摘要 : 超声喷射质量分辨激发光谱用于确定苯甲醇和一系列九种甲基-、乙基-、氟-和氨基苯甲醇的最小能量构象。对这些分子的飞行时间质谱 (TOFMS) 的解释导致为每个系统分配特定的分子几何形状。-CH2O 部分的最小能量构象被确定为垂直于芳环平面。空间无阻碍的苯甲醇中的羟基质子指向苯环。羟甲基低频扭转运动的势能垒主要来自于 OH 基团和环的 pi 系统之间的内部氢键相互作用。(jg)
1,2,4,6-Cycloheptatetraene: the key intermediate in arylcarbene interconversions and related C7H6 rearrangements
作者:Robert J. McMahon、Christopher J. Abelt、Orville L. Chapman、Jeffery W. Johnson、Curtis L. Kreil、Jean Pierre LeRoux、Anne M. Mooring、Paul R. West