81389-87-9Relevant academic research and scientific papers
Catalytic Hydroetherification of Unactivated Alkenes Enabled by Proton-Coupled Electron Transfer
Knowles, Robert R.,Metrano, Anthony J.,Tsuchiya, Yuto,Tsui, Elaine
, p. 11845 - 11849 (2020/05/22)
We report a catalytic, light-driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible-light irradiation in the presence of an IrIII-based photoredox catalyst, a Br?nsted base catalyst, and a hydrogen-atom transfer (HAT) co-catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O?H bonds through a proton-coupled electron-transfer mechanism. This method exhibits a broad substrate scope and high functional-group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented.
De novo asymmetric synthesis of All-d-, All-l-, and d-/l-oligosaccharides using atom-less protecting groups
Babu, Ravula Satheesh,Chen, Qian,Kang, Sang-Woo,Zhou, Maoquan,O'Doherty, George A.
, p. 11952 - 11955 (2012/09/07)
Oligosaccharide synthesis is hindered by the need for multiple steps as well as numerous selective protections and deprotections. Herein we report a highly efficient de novo route to various oligosaccharide motifs, of use for biological and medicinal structure activity studies. The key to the overall efficiency is the judicious use of asymmetric catalysis and synthetic design. These green principles include the bidirectional use of highly stereoselective catalysis (Pd(0)-catalyzed glycosylation/post-glycosylation). In addition, the chemoselective use of C-C and C-O π-bond functionality, as atom-less protecting groups as well as an anomeric directing group (via a Pd-π-allyl), highlights the atom-economical aspects of the route to a divergent set of natural and unnatural oligosaccharides (i.e., various d-/l-diastereomers of oligosaccharides as well as deoxysugars which lack C-2 anomeric directing groups). For example, in only 12 steps, the construction of a highly branched heptasaccharide with 35 stereocenters was accomplished from an achiral acylfuran.
Synthesis of macrocyclic scaffolds suitable for diversity-oriented synthesis of macrolides
Grimwood, Michael E.,Hansen, Henrik C.
supporting information; experimental part, p. 8132 - 8138 (2010/01/16)
Synthesis of macrocyclic glycal-based scaffolds for diversity-oriented synthesis was studied and demonstrated using macrocyclic enyne ring-closing metathesis. The roles of ring size, alkyne substitution, and orientation relative to the glycal were studied. In all cases, the cyclization showed preference for the thermodynamically favored endo-mode of closure and a trans-double bond at the ring-closure site, leaving macrocyclic scaffolds all containing multiple orthogonal functional groups available for further diversification.
Highly deoxygenated sugars. I. C2-branched glucose derivatives and carbon linked deoxygenated disaccharides
Krohn, Karsten,Floerke, Ulrich,Gehle, Dietmar
, p. 431 - 443 (2007/10/03)
Triacetylglucal (1) is converted with high α-selectivity (>9:1) to the corresponding 2,3-unsaturated allyl and benzyl glycosides 2 and 3 using ferric chloride as the catalyst. The 6-O-silyl-protected allylic alcohol 5 is transformed to the 3,4-unsaturated C2-branched ester 6 or the amide 7 by Claisen rearrangement. The highly deoxygenated iodo lactone 8, resulting from the amide 6 by iodolactonization, is a versatile starting material for chiral building blocks 9-12. The 3,4-unsaturated C2-branched ester 6 is reduced to the aldehyde 14 and converted to a carbon linked disaccharide analogue 16 via cycloaddition with Danishefky's diene.
Synthesis of Benzannelated Pyranosides
Card, Peter J.
, p. 2169 - 2173 (2007/10/02)
Ethyl and benzyl 2,3-dideoxy-α-D-glycero-hex-2-enopyranosid-4-uloses (e.g., 9-11) were prepared from D-glucal.The enones reacted with 1-methoxy-1,3-butadiene or 1--1,3-butadiene to afford the corresponding cycloadducts.DDQ aromatization and subsequent elaboration of the cycloadducts gave benzannelated pyranosides.Amino sugar derivatives also were prepared.Aromatization of the (trimethylsilyl)oxy adducts directly afforded the corresponding phenols, but the reaction was found to be of limited scope.The stereochemistry of intermediates and products and subtleties of the DDQ reaction are discussed.
