Switching between <i>X</i>-Pyrano-, <i>X</i>-Furano-, and Anhydro-<i>X</i>-pyranoside Synthesis (X = C, N) under Lewis acid Catalyzed Conditions
作者:Youngran Seo、Jared M. Lowe、Neyen Romano、Michel R. Gagné
DOI:10.1021/acs.orglett.1c01713
日期:2021.8.6
A variety of C-glycosides can be obtained from the fluoroarylborane (B(C6F5)3) or silylium (R3Si+) catalyzed functionalization of 1-MeO- and per-TMS-sugars with TMS-X reagents. A one-step functionalization with a change as simple as the addition order and/or Lewis acid and TMS-X enables one to afford chiral synthons that are common (C-pyranosides), have few viable synthetic methods (C-furanosides)
各种C-糖苷可以从氟芳基硼烷(B(C 6 F 5 ) 3 )或硅基(R 3 Si + )催化的1-MeO-和全TMS-糖与TMS-X试剂的官能化获得。一步功能化只需简单地改变加成顺序和/或路易斯酸和 TMS-X,即可获得常见的手性合成子( C-吡喃糖苷),但几乎没有可行的合成方法( C-呋喃糖苷),或实际上是未知的(脱水-C-吡喃糖苷),其机械地分别由是否发生直接取代、异构化/取代或取代/异构化而产生。
Modulating Electrostatic Interactions in Ion Pair Intermediates To Alter Site Selectivity in the C−O Deoxygenation of Sugars
作者:Jared M. Lowe、Bekah E. Bowers、Youngran Seo、Michel R. Gagné
DOI:10.1002/anie.202007415
日期:2020.9.21
oligosaccharides. Computational methods helped identify this non‐intuitive outcome in low dielectric solvents to non‐isotropic electrostatic enhancements in the key ion pair intermediates, which influence the reaction coordinate in the reactivity‐/selectivity‐determining step. Molecular‐level models for these effects have far‐reaching consequences in stereoselective ion pair catalysis.
Borane- and Silylium-Catalyzed Difunctionalization of Carbohydrates: 3,6-Anhydrosugar Enabled 1,6-Site Selectivity
作者:Joshua J. Clarke、Kevin Basemann、Neyen Romano、Stephen J. Lee、Michel R. Gagné
DOI:10.1021/acs.orglett.2c01243
日期:2022.6.17
A novel diastereoselective, Lewis acid catalyzed 1,6-difunctionalization of galactose and mannose derivatives has been developed in one pot, via sequential nucleophile additions. Our studies point to the formation of a 3,6-anhydrosugar intermediate as key to the 1,6-site-selectivity. Starting material-specific reactivity occurs when competitive ring-opening C–O cleavage is possible, owed to basicity
Silicon-29 NMR spectroscopy in carbohydrate chemistry: Galactose derivatives
作者:D. J. Gale、N. A. Evans
DOI:10.1002/omr.1270210910
日期:1983.9
Abstract29Si NMR spectra of the O‐trimethylsilyl (OTMS) derivatives of various methyl α‐ and β‐D‐galactopyranosides have been recorded. The effect of changes in the anomeric configuration provides a means of assigning the resonance of the 2‐OTMS substituent. Whereas the signal of the OTMS group attached at the 6‐position can be assigned readily, those of the OTMS group at the 3‐ or 4‐position cannot be assigned unequivocally.
Synthesis of feruloylated and p-coumaroylated methyl glycosides