22415-59-4Relevant articles and documents
New route to enantiomers of cyclic β-hydroxyethers. The crystal structure of (S)-(+)-tetrahydrofurfuryl-O,O'-diacetyl-(2R,3R)-hydrogentartrate
Mravik, Andras,Boecskei, Zsolt,Keszei, Sandor,Elekes, Ferenc,Fogassy, Elemer
, p. 1477 - 1484 (1996)
Title compounds 1-2 were readily resolved into their enantiomers by crystallizing their half esters formed with O,O'-diacetyl-(2R,3R)-tartaric acid. An intermolecular H-bond between the free carboxyl group and the ring oxygen, determined by single crystal X-ray study of (S)-(+)-tetrahydrofurfuryl-O,O'-diacetyl-(2R,3R)-hydrogentartrate, enhances the selectivity and the crystallizing ability itself.
C-2 auxiliaries for stereoselective glycosylation based on common additive functional groups
Boltje, Thomas J.,De Kleijne, Frank F. J.,Moons, Sam J.,White, Paul B.
, p. 1165 - 1184 (2020/02/22)
The stereoselective introduction of the glycosidic bond is one of the main challenges in chemical oligosaccharide synthesis. Stereoselective glycosylation can be achieved using neighbouring group participation of a C-2 auxiliary or using additives, for example. Both methods aim to generate a defined reactive intermediate that reacts in a stereoselective manner with alcohol nucleophiles. This inspired us to develop new C-2 auxiliaries based on commonly used additive functionalities such as ethers, phosphine oxides and tertiary amides. Good 1,2-trans-selectivity was observed for the phosphine oxide and amide-based auxiliaries expanding the toolbox with new auxiliaries for stereoselective glycosylation reactions.
Anti-Selective Catalytic Asymmetric Nitroaldol Reaction of α-Keto Esters: Intriguing Solvent Effect, Flow Reaction, and Synthesis of Active Pharmaceutical Ingredients
Karasawa, Tomoya,Oriez, Rapha?l,Kumagai, Naoya,Shibasaki, Masakatsu
supporting information, p. 12290 - 12295 (2018/09/27)
A rare-earth metal/alkali metal bimetallic catalyst proved particularly effective for enantioselectively coupling nitroalkanes and α-keto esters in an anti-selective manner to afford synthetically versatile, densely functionalized, and optically active α-nitro tertiary alcohols. A chiral diamide ligand captured two distinct metal cations, giving rise to a catalytically competent solid-phase heterobimetallic catalyst by simple mixing via self-assembly. The advantage of the solid-phase asymmetric catalyst was realized by successful application to the enantio- and diastereoselective reaction in a continuous-flow platform. The use of closely related solvents in terms of structures and polarity parameters, THF and its methylated congener 2-Me-THF, had an unexpectedly large solvent effect both on the reaction rate and the stereoselectivity. The nitroaldol products share a privileged unit for active pharmaceutical ingredients, as demonstrated by the streamlined enantioselective synthesis of the marketed antifungal agents efinaconazole and albaconazole.
