Catalytic activation of glycosyl phosphates for stereoselective coupling reactions
作者:Samuel M. Levi、Qiuhan Li、Andreas R. Rötheli、Eric N. Jacobsen
DOI:10.1073/pnas.1811186116
日期:2019.1.2
Glycosyl phosphates are shown to be activated to stereospecific nucleophilic substitution reactions by precisely tailored bis-thiourea catalysts. Enhanced reactivity and scope is observed with phosphate relative to chloride leaving groups. Stronger binding (Km) to the H-bond donor and enhanced reactivity of the complex (kcat) enables efficient catalysis with broad functional group compatibility under
Efficient O-Functionalization of Carbohydrates with Electrophilic Reagents
作者:Gergely L. Tolnai、Ulf J. Nilsson、Berit Olofsson
DOI:10.1002/anie.201605999
日期:2016.9.5
iodonium(III) reagents. Both electron‐withdrawing and electron‐donating aryl groups were introduced under ambient conditions and without precautions to exclude air or moisture. Furthermore, the approach was extended both to full arylation of cyclodextrin, and to trifluoroethylation of carbohydrate derivatives. This is the first general approach to introduce traditionally non‐electrophilic groups into
5-disubstituted-α-D-glucofuranose proceeds with very high stereoselectivity to give stereochemically pure phosphinic and phosphinous acid esters, which are starting reagents for preparation of chiral organophosphoruscompounds. Stereoselectivity of the reaction depends on the nature of bases, solvent, temperature and excess of chlorophosphine.
Several monodentate phosphites derived from D-glucofuranose were prepared and examined as ligands in the rhodium catalysed enantioselective hydrosilylation of acetophenone. A substantial Variation in the e.e. values, from racemic to 58% e.e., was seen depending on the nature of the phosphite ligand used and the ligand to metal ratio. The reactivity of the selected phosphite P(DAG)(3) towards [Rh(mu -Cl)(COD)](2) and [Rh(mu -Cl)(C2H4)(2)](2) (DAG=(1:2;5:6)-di(O-isopropylidene)-D-glucofuranosyl) allowed the synthesis of monosubstitued Rh(Cl)(COD)P(dag), and [Rh(mu -Cl)(C2H4)P(dag)(3)](2) complexes, and the disubstituted Rh(Cl)(P(dag)(3))(2) and Rh(Cl)(C2H4)(P(dag)(3))(2) complexes. This study indicated that the disubstituted compounds offer better enantioselectivities than the monosubstituted ones. (C) 2001 Elsevier Science Ltd. All rights reserved.
Dynamic Kinetic Resolution of Bis-Sulfinyl Chlorides: A General Enantiodivergent Synthesis of <i>C</i><sub>2</sub>-Symmetric Bis-Sulfinate Esters and Bis-Sulfoxides