Leveraging on the orchestrated application of both Schmidt and Yu glycosylations, the first total syntheses of the echinocystic acid saponins pithedulosides D and E, the two antitumoral and ...representative D‐ring‐functionalized oleanane‐type saponins, were achieved. Benefitting from the applied convergent synthetic strategy, the echinocystic acids could be synthesized in overall yields of as high as 71 and 76 % through four linear steps.
The first total syntheses of the bioactive echinocystic acid saponins pithedulosides D and E are achieved by a convergent strategy using glycoysyl trichloroacetimidate and a glycosyl ortho‐alkynylbenzoate as donors.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
With easily available monosaccharides and steviol as starting materials, the first total synthesis of rebaudioside R with a xylosyl core in the C13-OH linked sugar chain was accomplished
via
two ...distinct approaches. The first approach features the stepwise installation of branch-sugar residues
via
an order of C2-OH first and then C3-OH of the xylosyl core, laying a firm foundation for the synthesis of analogues with different branch sugars, while the second route features the introduction of the C13 trisaccharide sugar chain
via
a convergent strategy, securing the overall synthetic efficiency. Through the synthetic study, the effect of protecting groups (PGs) at the vicinal hydroxy group on the reactivity of OH acceptors was illustrated.
The first total synthesis of rebaudioside R has been achieved
via
two different approaches.
An oxidative coupling reaction of fluoroalkylamines with arylboronic acids has been achieved for the first time. Fluorine has profound influence on the reactivity and fluoroalkylated amines have the ...following reactivity trend: difluoroethylamine > trifluoroethylamine > pentafluoropropylamine ≈ heptafluorobutylamine.
We have developed a dual copper/photoredox-catalyzed approach for the construction of the P(O)–N bond from commercially available aromatic amines and P(O)–H compounds. This metallaphotoredox method ...avoids toxic or corrosive reagents and does not require prefunctionalized substrates. The reaction has a broad substrate scope and is suitable for the synthesis of phosphonamides and phosphinamides, thus complementing the previous nonphotochemical approaches. The reaction is amenable to the direct modification of drug molecules and can be conducted on a gram scale.
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IJS, KILJ, NUK, PNG, UL, UM
A convenient and straightforward synthesis of diverse 2-C-alkenyl-glycosides through a palladium-catalyzed cross-coupling reaction between 2-iodoglycals and N-tosylhydrazones has been developed. ...Further transformation of 2-C-branched sugars by Diels–Alder reactions provided oxadecalins in good yields.
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We report for the first time that the imidate radical can be efficiently added to glycals to generate glycosyl radicals, based on which a general, toxic-reagent-free synthesis of C-glycosides of ...2-deoxy-2-amino sugars has been developed. Complementary to previous strategies, the reaction is 1,2-trans-stereoselective and could use aryl alkenes as substrates. The late-stage functionalization and density functional theory calculations are reported.
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With easily accessible and operator-friendly reagents, shelf-stable ortho-methoxycarbonylethynylphenyl thioglycosides were efficiently prepared. Based on these MCEPT glycoside donors, a novel ...glycosylation protocol featuring mild and catalytic promotion conditions with Au(I) or Cu(II) complexes, expanded substrate scope encompassing challenging donors and acceptors and clinically used pharmaceuticals, and versatility in various strategies for highly efficient synthesis of glycosides has been established. The practicality of the MCEPT glycosylation protocol was fully exhibited by highly efficient and scalable synthesis of surface polysaccharide subunits of Acinetobacter baumannii via latent–active, reagent-controlled divergent orthogonal one-pot and orthogonal one-pot strategies. The underlying reaction mechanism was investigated systematically through control reactions, leading to the isolation and characterization of the vital catalyst species in MCEPT glycosylation, the benzothiophen-3-yl-gold(I) complex. Based on the results obtained both from control reactions and from studies leading to the glycosylation protocol establishment, an operative mechanism was proposed and the effect of the vital catalyst species reactivity on the results of metal-catalyzed alkyne-containing donor-involved glycosylation was disclosed. Moreover, the mechanism for C-glycosylation side product formation from ortho-(substituted)ethynylphenyl thioglycoside donors with electron-donating substituents was also illuminated.
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By turning on or switching off the directing effect of the C3–OH-located o-diphenylphosphanylbenzoyl (o-DPPB) group in glycals, a reagent-controlled protocol for divergent and regio- and ...stereoselective syntheses of C-glycosides has been established. In particular, the silence of the directing effect of o-DPPB was achieved by the introduction of a ZnCl2 additive, which is operationally simple and efficient. The flexibility of the novel protocol was exhibited not only by the easy access of both α- and β-C-glycosides but also by the versatility of the obtained formal Ferrier rearrangement products, which can be easily derivatized to various C-glycoside analogues owing to the embedded multifunctionalities.
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With 8-(methyltosylaminoethynyl)-1-naphthyl (MTAEN) glycoside as donors, a novel and efficient glycosylation protocol has been established. The MTAEN glycosylation protocol exhibits the merits of ...shelf-stable donors, mild catalytic promotion conditions, considerably extended substrate scope encompassing both free alcohols, silylated alcohols, nucleobases, primary amides, and C-type nucleophile acceptors, and applicability to various one-pot strategies for highly efficient synthesis of oligosaccharides, such as orthogonal one-pot, single-catalyst one-pot, and acceptor reactivity-controlled one-pot strategies.
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By taking full advantage of the mild promotion conditions of an ortho-alkynylbenzoate glycosylation protocol, a highly efficient approach to construct the challenging (epi)-podophyllotoxin ...4-O-glycosidic linkages was devised under the activation of a catalytic amount of a Au(I) complex. The novel method enjoys a quite broad substrate scope in terms of both glycosyl donors and podophyllotoxin derivative acceptors, providing the desired glycosides in excellent yields. Based on the new approach, concise syntheses of clinically used anticancer reagents etoposide and teniposide were accomplished, and the overall yields counting from easily available starting materials could reach as high as 18% and 9%, respectively.
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