Chemical synthesis of β-d-psicofuranosyl disaccharides
摘要:
Disaccharides composed of a beta-D-psicofuranosyl unit were prepared by the glycosylation reaction of monosaccharide acceptors including three 23,4,6-tetra-O-protected hexopyranoses with a D-psicofuranosyl benzyl phthalate derivative (4). A beta-D-psicofuranosidic bond was formed by the TMSOTf-promoted reaction with high selectivity. Removal of the O-protecting groups from the resulting a-D-hexopyranosyl beta-D-psicofuranosides furnished the first chemical synthesis of alpha-D-gluco-, alpha-D-galacto-, and et-D-mannopyranosyl beta-D-psicofuranosides. The common beta-D-psicofuranosyl donor 4 was derived efficiently from D-psicose in five steps. (C) 2010 Elsevier Ltd. All rights reserved.
A polarimetric and 11B and 13C nuclear magnetic resonance study of the reaction of the tetrahydroxyborate ion with polyols and carbohydrates
作者:J. Graham Dawber、Stuart I. E. Green、John C. Dawber、Sundus Gabrail
DOI:10.1039/f19888400041
日期:——
reactions is demonstrated by 11B n.m.r. studies. A calibration method devised to relate peak area in 11B n.m.r. spectra with concentration has been used to calculate equilibrium constants for the various equilibria present, and an attempt has been made to rationalise the equilibrium constants with the molecular structures of the substrates. In the majority of cases the 13Cn.m.r. spectra confirm the polarimetric
四羟基硼酸根离子B(OH)– 4与31种多元醇和碳水化合物在水溶液中的反应已通过补充研究,包括偏光法和11 B和13 C nmr光谱学进行了研究。由于在许多情况下存在多重平衡,使用先前推导的方程式,通过极化分析结果计算出碳水化合物与B(OH)– 4络合的平衡常数仅获得了部分成功。通过11 B nmr研究证明了这些反应中几种复合物的存在。校准方法旨在关联11中的峰面积具有浓度的B nmr光谱已用于计算存在的各种平衡的平衡常数,并已尝试通过底物的分子结构合理化平衡常数。在大多数情况下,13 C nmr光谱证实了极化和11 B nmr研究,并且在大多数情况下,可以对多元醇/碳水化合物中的反应位点进行更具体的鉴定。
Chemical synthesis of β-d-psicofuranosyl disaccharides
Disaccharides composed of a beta-D-psicofuranosyl unit were prepared by the glycosylation reaction of monosaccharide acceptors including three 23,4,6-tetra-O-protected hexopyranoses with a D-psicofuranosyl benzyl phthalate derivative (4). A beta-D-psicofuranosidic bond was formed by the TMSOTf-promoted reaction with high selectivity. Removal of the O-protecting groups from the resulting a-D-hexopyranosyl beta-D-psicofuranosides furnished the first chemical synthesis of alpha-D-gluco-, alpha-D-galacto-, and et-D-mannopyranosyl beta-D-psicofuranosides. The common beta-D-psicofuranosyl donor 4 was derived efficiently from D-psicose in five steps. (C) 2010 Elsevier Ltd. All rights reserved.
High Throughput Electrochemical Observation of Structural Phase Changes in LiFe[sub 1−x]Mn[sub x]PO[sub 4] during Charge and Discharge
作者:Matthew R. Roberts、Girts Vitins、Guy Denuault、John R. Owen
DOI:10.1149/1.3294564
日期:——
Electrochemical lithium extraction and insertion in LiFe1-xMnxPO4 has been investigated by high throughput cyclic voltammetry on an array of samples with different degrees of carbon coating to assist electron transfer. A linear decrease in the capacity was observed with an increase in the value of x and was explained by a gradual loss of electronic conductivity due to the manganese substituent. Slow
已经通过高通量循环伏安法对一系列具有不同程度碳涂层以辅助电子转移的样品研究了 LiFe1-xMnxPO4 中的电化学锂提取和嵌入。随着 x 值的增加,观察到容量的线性下降,这可以用由于锰取代基导致的电子导电性逐渐丧失来解释。慢扫描伏安图显示了对应于 LiFePO4 中的异相(两相)反应和 LiFe0.2Mn0.8PO4 中铁的均相(单相)反应的峰形差异,说明了对伏安图的一般解释以区分这些机制。