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The reaction of 4, 6-O-benzylidene-D-pyranosides with a stoichiometric amount of TsCl, AcCl, and BzCl in the presence of silver(I) oxide and a catalytic amount of potassium iodide led to monosubstituted derivatives in high regioselectivity and in good yields.

An oligosaccharides library of small tri- and tetrasaccharides is prepared by one-pot sequential glycosylation strategies using thioglycosides as glycosylation reagents. The methodology facilitates rapid assembly of 33 linear or branched protected oligosaccharides.

A novel method for the synthesis of unsymmetrically 3,4-disubstituted thiophenes was developed based on the intermolecular thiazole-alkyne Diels-Alder reactions involving 3,4-bis(trimethylsilyl)thiophene. The synthetic strategy was characterized by the formation of the [2+2]- and [4+2]-cycloaddition adducts of 3,4-didehydrothiophene via 1,3-dipolar cycloadditions. Furthermore, the synthetic process was characterized by 3,4-bromothiophene modification and intermolecular thiazole-alkyne Diels-Alder reactions with 3,4-bis(trimethylsilyl)thiophene.

Two asymmetrically branched oligosaccharides, [Lewis.sup.x] and dimeric [Lewis.sup.x], are assembled in one pot with high yields and exclusive regio- and stereoselectivities, where p-tolyl thioglycosides are used as the sole type of building blocks. The reactivity-independent nature of the preactivation based method has allowed modular assembly of the dimeric Lewis octasaccharide.

Two efficient routes are described for the rapid assembly of the tumor-associated carbohydrate antigen Globo-H hexasaccharide by a preactivation based iterative one-pot strategy. Both the methods have shown that oligosaccharides containing [alpha] and [beta] linkages within the same molecule can be constructed in one pot through a preactivation based approach with higher glyco-assembly efficiencies than the automated solid-phase synthesis strategy.

A study was conducted to analyze the one-pot preparation of oligosaccharides by determining the reactivity of a number of p-methylphenyl thioglycoside donors. The relative reactivities of a series of glycoside donors were quantified. A database of thioglycosides as glycosyl donors was then developed using reactivity data. In addition, the reactivity of each monomer was determined separately by defining the relative reactivity value as a relative measure of reactivity for a given monosaccharide or disaccharide.

An effective library approach to oligosaccharides is described using a designed building block with four selectively removable protecting groups as the core for the source of acceptors and high-yielding coupling with different donors. The monosaccharide building block with four selectively removable protecting groups was designed to demonstrate the feasibility of the strategy. Results demonstrate that an effective orthogonal strategy for the synthesis of a library of oligosaccharides as individual entities has been developed.

Evidence concerning the existence of 3,4-didehydrothiophene as a synthetic intermediate has been obtained. The five-membered cyclic cumulene, which was characterized using the complete-active-space self-consistent field method, was prepared from phenyl 4-(trimethylsilyl)thien-3-yl iodonium triflate which, in turn, was synthesized from 3,4-bis(trimethylsilyl)thiophene. Its existence was confirmed by the generation of its (2 + 2)- and (4 + 2)-cycloaddition adducts with dienes.

Reports that the assembly of an oligosaccharide library has been achieved in a practical and efficient manner. Application of a one-pot sequential approach; Rapid assembly of 33 linear or branched fully-protected oligosaccharides using designed building blocks; Deprotection of the oligosaccharides either partially or completely to create 29 more structures.

Despite hypersialylation of cancer cells together with a significant upregulation of sialyltransferase (ST) activity contributes to the metastatic cascade at multiple levels, there are few dedicated tools to interfere with their expression. Although transition state-based ST inhibitors are well-established, they are not membrane permeable. To tackle this problem, herein, we design and construct long-circulating, self-assembled core-shell nanoscale coordination polymer (NCP) nanoparticles carrying a transition state-based ST inhibitor, which make the inhibitor transmembrane and potently strip diverse sialoglycans from various cancer cells. In the experimental lung metastasis and metastasis prevention models, the nanoparticle device (NCP/STI) significantly inhibits metastases formation without systemic toxicity. This strategy enables ST inhibitors to be applied to cells and animals by providing them with a well-designed nanodelivery system. Our work opens a new avenue to the development of transition state-based ST inhibitors and demonstrates that NCP/STI holds great promise in achieving metastases inhibition for multiple cancers.

Carbohydrates play essential roles in various physiological and pathological processes. Trifluoromethylated compounds have wide applications in the field of medicinal chemistry. Herein, we report a practical and efficient trifluoromethylation of glycals by an electrochemical approach using CF 3 SO 2 Na as the trifluoromethyl source and MnBr 2 as the redox mediator. A variety of trifluoromethylated glycals bearing different protective groups are obtained in 60-90% yields with high regioselectivity. The successful capture of a CF 3 radical indicates that a radical mechanism is involved in this reaction.

An efficient and stereoselective one-pot, two-step tandem α-arylation of glycals from readily available aryl amines via stable diazonium salts has been developed. Moreover, the stereoselective preparation of the challenging β- C-glycosyl arenes by the anomerization of α- C-glycosides using HBF 4 is also described. This protocol has a broad substrate scope and a wide functional-group tolerance. It can be used for the gram-scale preparation of 3-oxo- C-glycosides, which are versatile substrates for the preparation of many biologically important C-glycosides.

Antibiotic resistance is one of the biggest threats to public health, and new antibacterial agents hence are in an urgent need to combat infectious diseases caused by multidrug-resistant (MDR) pathogens. Utilizing dimerization strategy, we rationally designed and efficiently synthesized a new series of small molecule dimeric lysine alkylamides as mimics of AMPs. Evaluation of these mimics against a panel of Gram-positive and Gram-negative bacteria including MDR strains was performed, and a broad-spectrum and potent compound 3d was identified. This compound displayed high specificity toward bacteria over mammalian cell. Time-kill kinetics and mechanistic studies suggest that compound 3d quickly eliminated bacteria in a bactericidal mode by disrupting bacterial cell membrane. In addition, lead compound 3d could inhibit biofilm formation and did not develop drug resistance in S. aureus and E. coli over 14 passages. These results suggested that dimeric lysine nonylamide has immense potential as a new type of novel small molecular agent to combat antibiotic resistance.

A ruthenium/C 3 -TunePhos catalytic system has been identified for highly efficient direct reductive amination of simple ketones. The strategy makes use of ammonium acetate as the amine source and H 2 as the reductant and is a user-friendly and operatively simple access to industrially relevant primary amines. Excellent enantiocontrol (>90% ee for most cases) was achieved with a wide range of alkyl aryl ketones. The practicability of this methodology has been highlighted by scalable synthesis of key intermediates of three drug molecules. Moreover, an improved synthetic route to the optimal diphosphine ligand C 3 -TunePhos is also presented.

A general approach to the synthesis of diverse heteroaryl-C-Δ 1,2 -glycosides has been developed by employing the Pd(OAc) 2 /CuI cocatalyzed direct cross-coupling of five-membered nitrogen heterocycles with 1-iodoglycals in a C-H activation manner. Using this method, 27 examples of heteroaryl-C-Δ 1,2 -glycosides, containing indoles, thiazoles, benzothiazoles, imidazoles, benzimidazoles, and benzoxazoles as aglycones were obtained in 43-99% yield.

In the new transition-state based sialyltransferase inhibitors, an amide group was placed at the corresponding C-2 position of CMP-sialic acid to mimic the geometry and charge distribution in the transition state, and simple aromatic or aliphatic rings were used instead of the sialic acid moiety. All synthetic compounds exhibited excellent α(2-6)-sialyltransferase inhibition, resulting in up to a 2600-fold higher affinity for the enzyme than CMP-Neu5Ac, suggesting that amide is a key element for simulating transition-state features.

An efficient protocol for the O-sialylation using thiosialoside donors under visible light photocatalysis was developed. Thiosialosides were activated under the irradiation with blue light in the presence of Ru(bpy)3(PF6)2 as photocatalyst, Umemoto's reagent as CF3 radical source and Cu(OTf)2 as an additive in acetonitrile/dichloromethane at -30 °C, and the subsequent reaction with glycosyl acceptors generally produced the desired sialosides in good to excellent yields with the satisfactory α-selectivity.

Some conserved glycans on the HIV envelope protein are targets of broadly neutralizing antibodies (bnAbs) of HIV. BnAbs provide a precise definition of broadly neutralizing epitopes on the envelope protein of HIV. These epitopes are promising for vaccine design. Many glycan-related antigens with high affinity to bnAbs have been tested as immunogens in vivo. However, it was found that no bnAb-like antibodies were induced. Vaccination with different immunogens containing the same neutralizing epitope may enhance the affinity maturation of antibodies which focus on the shared epitope. This combined immunization strategy showed great potential in peptide epitope-based vaccine design. However, it has not yet been explored on glycan-related epitopes to date. Herein, we take 2G12 as a model to validate this strategy on glycan-related epitopes. A high-affinity antigen of 2G12 was constructed by conjugating the D1 arm tetramannoside to bovine serum albumin. Then, the glycoconjugate was coimmunized with a recombinant gp120, which was expected to selectively benefit the induction of antibodies recognizing the neutralizing epitope of 2G12 on gp120. Mice were inoculated with the two antigens simultaneously or alternately to determine the suitable regimen for this strategy. The serological assays demonstrated that the antibody titers and subtypes responded to the whole gp120 were not improved, and the proportion of antibodies competitively bound to the 2G12 epitope was not enhanced significantly either. However, the coimmunized glycoconjugate selectively raised the proportion of antibodies recognizing D1 arm tetramannoside-related structures on gp120. These results provide important experience for the design of glycan-dependent bnAb-based vaccines.

A monoselective synthesis of aryl-C-Δ(1,2)-glycosides from 1-iodoglycals via palladium-catalyzed ortho-C-H activation of N-quinolyl benzamides has been developed. An amino acid derivative was used as a crucial ligand to improve the yield and monoselectivity of the coupling reaction. The utility of this protocol was demonstrated by a concise synthesis of key moieties of some natural products.

A mild and convenient transformation for the synthesis of nitro-polyols is described. The nitro-polyol derivatives were prepared either from 2-nitroglycals via a pyridine-promoted scission of the carbon-carbon double bond or from glycals via a sequential nitration-scission procedure. The generated nitro-polyols could undergo a stereoselective Michael addition reaction. The utility of the addition products was exemplified by the concise synthesis of (-)-hyacinthacine A1 and 7a-epi-(-)-hyacinthacine A1.

A glycosyl coupling reaction via photoinduced direct activation of thioglycosides and subsequent O-glycosylation in the absence of photosensitizer was developed for the first time. This reaction underwent a selectively homolytic cleavage of a C-S bond to generate a glycosyl radical, which was oxidized to an oxacarbenium ion by Cu(OTf)2, and a sequential O-glycosylation. A wide range of glycosides were synthesized in moderate to excellent yield using sugars, amino acids, or cholesterol as the acceptors.

A mild, efficient, and practical transformation for the direct C-H trifluoromethylation of glycals under visible light has been reported for the first time. This reaction employed fac-Ir(3+)(ppy)3 as the photocatalyst, Umemoto's reagent as the CF3 source, and a household blue LED or sunlight as the light source. Glycals bearing both electron-withdrawing and -donating protective groups performed this reaction smoothly. This visible light-mediated trifluoromethylation reaction was highlighted by the trifluoromethylation of the biologically important Neu2en moiety.