74372-91-1Relevant academic research and scientific papers
Light-Mediated Cross-Coupling of Anomeric Trifluoroborates
Miller, Eric M.,Walczak, Maciej A.
, p. 4289 - 4293 (2021/06/28)
Stereoselective reactions at the anomeric carbon constitute the cornerstone of preparative carbohydrate chemistry. Here, we report stereoselective C-arylation and etherification reactions of anomeric trifluoroborates derived from BMIDA esters. These react
Glycosyl Cross-Coupling of Anomeric Nucleophiles: Scope, Mechanism, and Applications in the Synthesis of Aryl C-Glycosides
Zhu, Feng,Rodriguez, Jacob,Yang, Tianyi,Kevlishvili, Ilia,Miller, Eric,Yi, Duk,O'Neill, Sloane,Rourke, Michael J.,Liu, Peng,Walczak, Maciej A.
, p. 17908 - 17922 (2017/12/26)
Stereoselective manipulations at the C1 anomeric position of saccharides are one of the central goals of preparative carbohydrate chemistry. Historically, the majority of reactions forming a bond with anomeric carbon has focused on reactions of nucleophiles with saccharide donors equipped with a leaving group. Here, we describe a novel approach to stereoselective synthesis of C-aryl glycosides capitalizing on the highly stereospecific reaction of anomeric nucleophiles. First, methods for the preparation of anomeric stannanes have been developed and optimized to afford both anomers of common saccharides in high anomeric selectivities. We established that oligosaccharide stannanes could be prepared from monosaccharide stannanes via O-glycosylation with Schmidt-type donors, glycal epoxides, or under dehydrative conditions with C1 alcohols. Second, we identified a general set of catalytic conditions with Pd2(dba)3 (2.5 mol%) and a bulky ligand (JackiePhos, 10 mol%) controlling the β-elimination pathway. We demonstrated that the glycosyl cross-coupling resulted in consistently high anomeric selectivities for both anomers with mono- and oligosaccharides, deoxysugars, saccharides with free hydroxyl groups, pyranose, and furanose substrates. The versatility of the glycosyl cross-coupling reaction was probed in the total synthesis of salmochelins (siderophores) and commercial anti-diabetic drugs (gliflozins). Combined experimental and computational studies revealed that the β-elimination pathway is suppressed for biphenyl-type ligands due to the shielding of Pd(II) by sterically demanding JackiePhos, whereas smaller ligands, which allow for the formation of a Pd-F complex, predominantly result in a glycal product. Similar steric effects account for the diminished rates of cross-couplings of 1,2-cis C1-stannanes with aryl halides. DFT calculations also revealed that the transmetalation occurs via a cyclic transition state with retention of configuration at the anomeric position. Taken together, facile access to both anomers of various glycoside nucleophiles, a broad reaction scope, and uniformly high transfer of anomeric configuration make the glycosyl cross-coupling reaction a practical tool for the synthesis of bioactive natural products, drug candidates, allowing for late-stage glycodiversification studies with small molecules and biologics.
Preparation of α-C-Glycosides from Glycals
Parrish,Daniel Little
, p. 1439 - 1442 (2007/10/03)
(matrix presented) A novel approach to simple C-glycosides is reported. Reductive ring opening of 1,2-anhydro sugars with titanocene(III) chloride produces an anomeric radical that can be trapped with a variety of agents. The reaction stereospecifically a
Rapid preparation of variously protected glycals using titanium(III)
Spencer, Roxanne P.,Cavallaro, Cullen L.,Schwartz, Jeffrey
, p. 3987 - 3995 (2007/10/03)
Glycosyl chlorides and bromides can be rapidly converted to glycals in high yield by reaction with (Cp2Ti[III]Cl)2. This reagent tolerates a wide range of common carbohydrate protecting groups, including silyl ethers, acetals, and esters; the methodology provides a general route for the preparation of glycals substituted with both acid- and base-labile functionality. A reaction mechanism is proposed that is based on heteroatom abstraction to give an intermediate glycosyl radical. This radical reacts with a second equivalent of Ti(III) to yield a glycosyltitanium(IV) species. β-Heteroatom elimination from the glycosyltitanium(IV) complex gives the glycal.
Synthesis and structure revision of intensely sweet saponin osladin
Yamada,Nishizawa
, p. 386 - 397 (2007/10/02)
The synthesis of compound 1, which is the reported structure of the intensely sweet saponin osladin, has been completed. However, it is not sweet at all. Extraction of the rhizomal sweet principle of the fern Polypodium vulgare (Polypodiaceae) and a singl
