Topic
Glycal
About: Glycal is a research topic. Over the lifetime, 897 publications have been published within this topic receiving 17422 citations.
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TL;DR: The utility of N-glycosyl trichloroacetamides as robust and versatile intermediates in the synthesis of unsymmetrical urea-linked disaccharides and trisaccharide is demonstrated and the method for the stereoselective synthesis of alpha- and beta- glycosyl ureas via Pd(II)-catalyzed rearrangement of glycal trich chloroacetimidates is developed.
Abstract: The research on the area of glycosyl urea derivatives, in which the O- and N-glycosidic bonds are replaced with the urea-glycosidic linkages, has recently emerged with applications in the field of aminoglycoside antibiotics. We have developed a novel method for the stereoselective synthesis of α- and β-glycosyl ureas via Pd(II)-catalyzed rearrangement of glycal trichloroacetimidates. In our approach, the α- and β-selectivity at the anomeric carbon of N-glycosyl trichloroacetamides depends on the nature of the palladium−ligand catalyst. While the cationic Pd(II)-L-4 (2-trifluoroacetylphenol) complex promotes α-selectivity, the neutral Pd(II)-TTMPP-L-5 (4-chloro-2-trifluoroacetylphenol) complex favors β-selectivity. The resulting α- and β-N-glycosyl trichloroacetamides were further coupled with a diverse array of primary and hindered secondary nitrogen nucleophiles to provide the corresponding glycosyl ureas in moderate to good yields and with no loss of stereochemical integrity at the anomeric carbon. We h...
31 citations
Abstract: Syntheses of 8-ethenyl-1-hydrory-4-β-D-ribofuranosylbenzo[d]naphtho[1,2-b]pyran-6-one (1) and 8-ethenyl- 1-hydrory-4-(2'-deoxy-β-ribofuranosyl)benzo[d]naphtho[1,2-b]pyran-6-one (2) have been accomplished. These two compounds are the first synthetic C-glycosides structurally related to the gilvocarcin, ravidomycin, and chrysomycin antibiotic class which possess the aglycon substituents (hydroxyl at C-1 and ethenyl at C-8) considered critical for the photolytic nicking of DNA.Anthracycline C-glycoside 1 was prepared by a route involving Lewis acid-catalyzed C-glycosyl bond formation between the tetracyclic aglycon and 1,2,3,5-tetra-O-acetyl-D-ribose followed by construction of the aglycon 8-ethenyl substituent from the corresponding ethyl group by radical bromination-dehydrobromination.Synthesis of C-glycoside 2 utilized a different, complementary procedure for C-glycosyl bond formation by palladium-mediated coupling of an iodoaglycon derivative with 1,4-anhydro-2-deoxy-3-O-(tert-butyldiphenylsilyl)-D-erythro-pent-1-enitol,a furanoid glycal designed to form only β C-glycosyl bonds in this reaction
31 citations
TL;DR: In this article, β-C-Galacto-Pyranosides with CHF and CF2 substitutes for the glycosidic oxygen were prepared through a four-step sequence starting from a central 1-thio-1,2-O-isopropylidene acetal alcohol and different α-fluoro- and α,α-difluoro acids.
30 citations
TL;DR: A new and highly efficient methodology for the construction of synthetically important highly O-functionalized enantiopure 2,3,4-trisubstituted tetrahydrofurans with three contiguous stereocenters is reported.
30 citations
TL;DR: Nucleoside 2-deoxyribosyltransferase is found to catalyze the hydration of D-ribal in the absence of nucleic acid bases and the synthesis of deoxyribonucleosides from ribal in their presence, affording a new method for the preparation of 2'-deoxy Ribon nucleosides.
Abstract: In the absence of acceptors nucleoside 2-deoxyribosyltransferase catalyzes the slow hydrolysis of 2'-deoxynucleosides. During this hydrolytic reaction, D-ribal (1,4-anhydro-2-deoxy-D-erythro-pent-1-enitol), a glycal of ribose hitherto encountered only as a reagent in organic synthesis, is generated spontaneously, disappearing later as 2'-deoxynucleoside hydrolysis approaches completion. Nucleoside 2-deoxyribosyltransferase is found to catalyze the hydration of D-ribal in the absence of nucleic acid bases and the synthesis of deoxyribonucleosides from ribal in their presence, affording a new method for the preparation of 2'-deoxyribonucleosides. The stereochemistry of nucleoside formation from ribal supports the intervention of deoxyribosyl-enzyme intermediate. The equilibrium constant for the covalent hydration of ribal is found to be approximately 65.
30 citations