An efficient synthesis of cyclodextrin-based carbohydrate cluster compounds

Glycoconjugations of Biomolecules by Chemical Methods

Bioconjugations under benign aqueous conditions have the most promise to covalently link carbohydrates onto chosen molecular and macromolecular scaffolds. Chemical methodologies relying on C-C and C-heteroatom bond formations are the methods of choice, coupled with the reaction conditions being under aqueous milieu. A number of methods, including metal-mediated, as well as metal-free azide-alkyne cyclo-addition, photocatalyzed thiol-ene reaction, amidation, reductive amination, disulfide bond formation, conjugate addition, nucleophilic addition to vinyl sulfones and vinyl sulfoxides, native chemical ligation, Staudinger ligation, olefin metathesis, and Suzuki-Miyaura cross coupling reactions have been developed, in efforts to conduct glycoconjugation of chosen molecular and biomolecular structures. Within these, many methods require pre-functionalization of the scaffolds, whereas methods that do not require such pre-functionalization continue to be few and far between. The compilation covers synthetic methodology development for carbohydrate conjugation onto biomolecular and biomacromolecular scaffolds. The importance of such glycoconjugations on the functional properties is also covered.

Construction of giant glycosidase inhibitors from iminosugar-substituted fullerene macromonomers

An ultra-fast synthetic procedure based on grafting of twelve fullerene macromonomers onto a fullerene hexa-adduct core was used for the preparation of a giant molecule with 120 peripheral iminosugar residues. The inhibition profile of this giant iminosugar ball was evaluated against various glycosidases. In the particular case of the Jack bean α-mannosidase, a dramatic enhancement of the glycosidase inhibitory effect was observed for the giant molecule with 120 peripheral subunits as compared to that of the corresponding mono- and dodecavalent model compounds.

Recent advances in photoinduced glycosylation: oligosaccharides, glycoconjugates and their synthetic applications

Carbohydrates have been demonstrated to perform imperative act in biological processes. This review highlights recent uses of photoinduced glycosylation in carbohydrate chemistry for the synthesis of oligosaccharides, thiosugars, glycoconjugates and glycoprotein.

Photoclick Hydrogels Prepared from Functionalized Cyclodextrin and Poly(ethylene glycol) for Drug Delivery and in Situ Cell Encapsulation

Polymers or hydrogels containing modified cyclodextrin (CD) are highly useful in drug delivery applications, as CD is a cytocompatible amphiphilic molecule that can complex with a variety of hydrophobic drugs. Here, we designed modular photoclick thiol-ene hydrogels from derivatives of βCD and poly(ethylene glycol) (PEG), including βCD-allylether (βCD-AE), βCD-thiol (βCD-SH), PEG-thiol (PEGSH), and PEG-norbornene (PEGNB). Two types of CD-PEG hybrid hydrogels were prepared using radical-mediated thiol-ene photoclick reactions. Specifically, thiol-allylether hydrogels were formed by reacting multiarm PEGSH and βCD-AE, and thiol-norbornene hydrogels were formed by cross-linking βCD-SH and multiarm PEGNB. We characterized the properties of these two types of thiol-ene hydrogels, including gelation kinetics, gel fractions, hydrolytic stability, and cytocompatibility. Compared with thiol-allylether hydrogels, thiol-norbornene photoclick reaction formed hydrogels with faster gelation kinetics at equivalent macromer contents. Using curcumin, an anti-inflammatory and anticancer hydrophobic molecule, we demonstrated that CD-cross-linked PEG-based hydrogels, when compared with pure PEG-based hydrogels, afforded higher drug loading efficiency and prolonged delivery in vitro. Cytocompatibility of these CD-cross-linked hydrogels were evaluated by in situ encapsulation of radical sensitive pancreatic MIN6 β-cells. All formulations and cross-linking conditions tested were cytocompatible for cell encapsulation. Furthermore, hydrogels cross-linked by βCD-SH showed enhanced cell proliferation and insulin secretion as compared to gels cross-linked by either dithiothreitol (DTT) or βCD-AE, suggesting the profound impact of both macromer compositions and gelation chemistry on cell fate in chemically cross-linked hydrogels.

Multivalent thioglycopeptoids via photoclick chemistry: potent affinities towards LecA and BC2L-A lectins

The straightforward access to peptoid-based multivalent thioglycoclusters displaying 1-thio-β-d-galactose or 1-thio-α/β-d-mannose and their evaluation towards two bacterial lectins are described.

Glyconanosynthons as powerful scaffolds and building blocks for the rapid construction of multifaceted, dense and chiral dendrimers

The arsenal of available carbohydrates can be manipulated to provide versatile building blocks toward the syntheses of complex and chiral dendrimers.

Dendrimers - from organic synthesis to pharmaceutical applications: an update

Dendrimers are a relatively new class of monodisperse polymers, which have tree-like spherical structures with well-defined sizes and shapes. Their unique structure has a significant impact on their physical and chemical properties. Research on dendrimers is of significant interest to scientists from all areas and their utility in various scientific fields, including pharmaceuticals, is expanding. The present review is comprehensive and covers different aspects of dendrimers viz. (1) synthesis, (2) properties and (3) pharmaceutical applications. The emphasis is on their applications as well as the current ongoing research status for drug targeting.

Cyclodextrin-based multivalent glycodisplays: covalent and supramolecular conjugates to assess carbohydrate-protein interactions

Covalent attachment of biorecognizable sugar ligands in several copies at precise positions of cyclomaltooligosaccharide (cyclodextrin, CD) macrocycles has proven to be an extremely flexible strategy to build multivalent conjugates. The commercial availability of the native CDs in three different sizes, their axial symmetry and the possibility of position- and face-selective functionalization allow a strict control of the valency and spatial orientation of the recognition motifs (glycotopes) in low, medium, high and hyperbranched glycoclusters, including glycodendrimer-CD hybrids. "Click-type" ligation chemistries, including copper(i)-catalyzed azide-alkyne cycloaddition (CuAAC), thiol-ene coupling or thiourea-forming reactions, have been implemented to warrant full homogeneity of the adducts. The incorporation of different glycotopes to investigate multivalent interactions in heterogeneous environments has also been accomplished. Not surprisingly, multivalent CD conjugates have been, and continue to be, major actors in studies directed at deciphering the structural features ruling carbohydrate recognition events. Nanometric glycoassemblies endowed with the capability of adapting the inter-saccharide distances and orientations in the presence of a receptor partner or capable of mimicking the fluidity of biological membranes have been conceived by multitopic inclusion complex formation, rotaxanation or self-assembling. Applications in the fields of sensors, site-specific drug and gene delivery or protein stabilization attest for the maturity of the field.

Design, synthesis and biological evaluation of carbohydrate-functionalized cyclodextrins and liposomes for hepatocyte-specific targeting

Targeting glycan-binding receptors is an attractive strategy for cell-specific drug and gene delivery. The C-type lectin asialoglycoprotein receptor (ASGPR) is particularly suitable for liver-specific delivery due to its exclusive expression by parenchymal hepatocytes. In this study, we designed and developed an efficient synthesis of carbohydrate-functionalized β-cyclodextrins (βCDs) and liposomes for hepatocyte-specific delivery. For targeting of ASGPR, rhodamine B-loaded βCDs were functionalized with glycodendrimers. Liposomes were equipped with synthetic glycolipids containing a terminal D-GalNAc residue to mediate binding to ASGPR. Uptake studies in the human hepatocellular carcinoma cell line HepG2 demonstrated that βCDs and liposomes displaying terminal D-Gal/D-GalNAc residues were preferentially endocytosed. In contrast, uptake of βCDs and liposomes with terminal d-Man or D-GlcNAc residues was markedly reduced. The d-Gal/d-GalNAc-functionalized βCDs and liposomes presented here enable hepatocyte-specific targeting. Gal-functionalized βCDs are efficient molecular carriers to deliver doxorubicin in vitro into hepatocytes and induce apoptosis.

Design and creativity in synthesis of multivalent neoglycoconjugates

From the authors' opinion, this chapter constitutes a modest extension of the seminal and inspiring contribution of Stowell and Lee on neoglycoconjugates published in this series [C. P. Stowell and Y. C. Lee, Adv. Carbohydr. Chem. Biochem., 37 (1980) 225-281]. The outstanding progresses achieved since then in the field of the "glycoside cluster effect" has witnessed considerable creativity in the design and synthetic strategies toward a vast array of novel carbohydrate structures and reflects the dynamic activity in the field even since the recent chapter by the Nicotra group in this series [F. Nicotra, L. Cipolla, F. Peri, B. La Ferla, and C. Radaelli, Adv. Carbohydr. Chem. Biochem., 61 (2007) 353-398]. Beyond the more classical neoglycoproteins and glycopolymers (not covered in this work) a wide range of unprecedented and often artistically beautiful multivalent and monodisperse nanostructures, termed glycodendrimers for the first time in 1993, has been created. This chapter briefly surveys the concept of multivalency involved in carbohydrate-protein interactions. The topic is also discussed in regard to recent steps undertaken in glycobiology toward identification of lead candidates using microarrays and modern analytical tools. A systematic description of glycocluster and glycodendrimer synthesis follows, starting from the simplest architectures and ending in the most complex ones. Presentation of multivalent glycostructures of intermediate size and comprising, calix[n]arene, porphyrin, cyclodextrin, peptide, and carbohydrate scaffolds, has also been intercalated to better appreciate the growing synthetic complexity involved. A subsection describing novel all-carbon-based glycoconjugates such as fullerenes and carbon nanotubes is inserted, followed by a promising strategy involving dendrons self-assembling around metal chelates. The chapter then ends with those glycodendrimers that have been prepared using commercially available dendrimers possessing varied functionalities, or systematically synthesized using either divergent or convergent strategies.

Poly-6-cationic amphiphilic cyclodextrins designed for gene delivery

A new series of amphiphilic cyclodextrins containing cationic groups at the 6-positions and alkyl or biolabile ester groups at the 2-positions has been synthesised. Selective 2-O-allylation followed by photochemical addition of lipophilic thiols made it possible to control lipophilicity in these mesomolecules and allow solubility and self-assembly in water. The cationic groups are cysteamine-derived, while the alkyl and ester groups are C(1)-C(16) and benzyl ester groups. This is a new general synthetic route to a potentially wide range of polycationic cyclodextrins capable of acting as gene delivery vectors by condensing DNA and forming liquid crystalline complexes with oligonucleotides.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update covering the period 2001-2002

This review is the second update of the original review on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates that was published in 1999. It covers fundamental aspects of the technique as applied to carbohydrates, fragmentation of carbohydrates, studies of specific carbohydrate types such as those from plant cell walls and those attached to proteins and lipids, studies of glycosyl-transferases and glycosidases, and studies where MALDI has been used to monitor products of chemical synthesis. Use of the technique shows a steady annual increase at the expense of older techniques such as FAB. There is an increasing emphasis on its use for examination of biological systems rather than on studies of fundamental aspects and method development and this is reflected by much of the work on applications appearing in tabular form.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update covering the period 1999-2000

This review describes the use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates and continues coverage of the field from the previous review published in 1999 (D. J. Harvey, Matrix-assisted laser desorption/ionization mass spectrometry of carbohydrates, 1999, Mass Spectrom Rev, 18:349-451) for the period 1999-2000. As MALDI mass spectrometry is acquiring the status of a mature technique in this field, there has been a greater emphasis on applications rather than to method development as opposed to the previous review. The present review covers applications to plant-derived carbohydrates, N- and O-linked glycans from glycoproteins, glycated proteins, mucins, glycosaminoglycans, bacterial glycolipids, glycosphingolipids, glycoglycerolipids and related compounds, and glycosides. Applications of MALDI mass spectrometry to the study of enzymes acting on carbohydrates (glycosyltransferases and glycosidases) and to the synthesis of carbohydrates, are also covered.

Cooperative lectin recognition of periodical glycoclusters along DNA duplexes: alternate hybridization and full hybridization

We describe herein the construction of periodically, spatially controlled glycoclusters along DNA duplexes and their cooperative lectin recognition. Site-specifically alpha-mannosylated oligodeoxynucleotide 20-mer (Man-ODN20) was synthesized via the phosphoramidite solid-phase synthesis. Alternate hybridization of the Man-ODN20 with the half-sliding complementary ODN 20-mer (hscODN20) gave an alternately prolonged Man-cluster Man-ODN20/hscODN20. The binding of the Man-cluster to FITC-labeled ConA lectin showed sigmoidal fluorescence dependency on the concentration of Man-ODN, indicating that some mannose residues along the repeating DNA duplex were cooperatively bound to ConA (apparent affinity constant: K(af)=2.4 x 10(4)M(-1) and Hill coefficient: n=3.5). The duplex of Man-ODN20 with full complementary ODN 20-mer (fcODN20) was little bound to ConA. The binding behavior of Man-ODN20/hscODN20 is compared with that of the alternately prolonged Gal-cluster Gal-ODN20/hscODN20 previously reported. Duplexes 20-mer, 40-mer, and 60-mer presenting one, two, and three periodic galactoses were also prepared by full hybridization of 20-mer beta-galactosylated oligodeoxynucleotide (Gal-ODN20) with the periodically repeating full complementary 20-mer, 40-mer, and 60-mer ODNs. RCA(120) lectin was found to little bind the 20-mer and 40-mer duplexes and to bind weakly and non-cooperatively the 60-mer duplex (K(af)=1.1 x 10(4)M(-1)). The cooperative lectin recognition of these glycoclusters in relation with the degree of association (DA) of ODN and the numbers of glycosides along the DNA duplex is discussed.

Synthesis and Lectin Binding Ability of Glycosamino Acid−Calixarenes Exposing GlcNAc Clusters

Novel calix[4 or 8]arene-based glycoconjugates exposing terminal N-acetyl-D-glucosamine clusters have been synthesized using amino acid-calixarenes as building blocks. The obtained glycosamino acid-calixarenes 9b-14b have lectin-binding ability and amplified inhibitory effects on erythrocyte agglutination induced by wheat germ (Triticum vulgaris) agglutinin (WGA). The inhibitory ability is dependent on the presence of the spacer and on the shape and rigidity of the calixarene skeleton.

Efficient Preparation of Glycoclusters from Silsesquioxanes

[structure: see text] A new type of glycocluster based on polyhedral oligosilsesquioxanes (POSS) has been efficiently prepared from unprotected mannoside and lactoside employing a convergent approach of thiol-radical addition reaction. The versatility of this approach was demonstrated by functionalization of mannosides and lactosides of different-length spacers.

Synthesis of lactoside glycodendrons using photoaddition and reductive amination methodologies

Carbohydrate-based divalent and tetravalent lactoside glycodendrons were constructed in a convergent manner. The dendrons were synthesized beginning with the photoaddition of hepta-O-acetyl-1-thio-beta-lactose, in an anti-Markovnikov manner, to a bis-allyl AB2 trisaccharide to form a divalent dendron. Following two nearly quantitative deprotection steps, the divalent lactoside was coupled to another AB2 trisaccharide by reductive amination to afford a tetravalent dendron. These paucivalent compounds were characterized by NMR spectroscopy and mass spectrometry.

Functional Evaluation of Carbohydrate-Centred Glycoclusters by Enzyme-Linked Lectin Assay: Ligands for Concanavalin A

The affinities of the mannose-specific lectin concanavalin A (Con A) towards D-glucose-centred mannosyl clusters differing in the anomeric configuration of the monosaccharide core, nature of the bridging functional groups and valency, have been measured by a competitive enzyme-linked lectin assay. Pentavalent thioether-linked ligands (5 and 7) were prepared by radical addition of 2,3,4,6-tetra-O-acetyl-1-thio-alpha-D-mannopyranose to the corresponding penta-O-allyl-alpha- or -beta-D-glucopyranose, followed by deacetylation. The distinct reactivity of the anomeric position in the D-glucose scaffold was exploited in the preparation of a tetravalent cluster (10) that keeps a reactive aglyconic group for further manipulation, including incorporation of a reporter group or attachment to a solid support. Hydroboration of the double bonds in the penta-O-allyl-alpha-D-glucopyranose derivative and replacement of the hydroxy groups with amine moieties gave a suitable precursor for the preparation of pentavalent and 15-valent mannosides through the thiourea-bridging reaction (17 and 20, respectively). The diastereomeric 1-thiomannose-coated clusters 5 and 7 were demonstrated to be potent ligands for Con A, with IC(50) values for the inhibition of the Con A-yeast mannan association indicative of 6.4- and 5.5-fold increases in binding affinity (valency-corrected values), respectively, relative to the value for methyl alpha-D-mannopyranoside. The tetravalent cluster 10 exhibited a valency-corrected relative lectin-binding potency virtually identical to that of the homologous pentavalent mannoside 7. In sharp contrast, replacement of the 1-thiomannose wedges of 5 with alpha-D-mannopyranosylthioureido units (17) virtually abolished any multivalent or statistic effects, with a dramatic decrease of binding affinity. The 15-valent ligand 20, possessing classical O-glycosidic linkages, exhibited a twofold increase in lectin affinity relative to the penta-O-(thioglycoside) 5; it is less efficient based on the number of mannose units. The results illustrate the potential of carbohydrates as polyfunctional platforms for glycocluster construction and underline the importance of careful design of the overall architecture in optimising glycocluster recognition by specific lectins.

Chemically defined sialoside scaffolds for investigation of multivalent interactions with sialic acid binding proteins

Four glycodendrons and a glycocluster were synthesized from carbohydrate building blocks to form paucivalent (di- to tetravalent) structures of controlled scaffold architectures. Enzymatic sialylation of the functionalized cluster and dendrons, terminated in lactose residues, generated a library of paucivalent synthetic sialosides displaying sialic acids with different dispositions. These newly constructed bioactive sialic acid-based structures were differentially recognized by sialoadhesin, a mammalian macrophage sialic acid binding protein. The binding of the sialosides to sialoadhesin was evaluated by an enzyme-linked immunosorbant assay to investigate the complementarity of scaffold structure and binding to sialoadhesin. Modulating the interaction between sialoadhesin and its sialic acid ligands has important implications in immunobiology.

Multivalent binding of galactosylated cyclodextrin vesicles to lectin

Amphiphilic beta-cyclodextrins with alkylthio chains at the primary-hydroxyl side and galactosylthio-oligo-(ethylene glycol) units at the secondary-hydroxyl side, which form nanoparticles and vesicles, show multivalent effects in their binding to lectin.

Synthesis of biantennary beta-D-(1-->6) glucosamine oligosaccharides

Biantennary beta-D-(1-->6) glucosamine hexa-, octa-, and dodecaoligosaccharide derivatives were synthesized convergently using isopropyl thioglycosides as donors in NIS/TMSOTf-catalyzed glycosylation.

Synthesis and characterization of mannosyl mimetic derivatives based on a beta-cyclodextrin core

The synthesis of branched beta-cyclodextrins substituted with mannosyl mimetic derivatives at one primary hydroxy group is described. It was shown that the self-inclusion phenomenon observed for the target compounds in water did not preclude the inclusion properties of the cyclodextrin moiety.

Macrocyclic glycoclusters. Self-aggregation and phosphate-induced agglutination behaviors of calix[4]resorcarene-based quadruple-chain amphiphiles with a huge oligosaccharide pool

Macrocyclic glycocluster compounds 2n (n = 2-7) with four alkyl (undecyl) chains and eight oligosaccharide moieties on the opposite sides of the calix[4]resorcarene macrocycle are prepared from the reactions of the corresponding octaamine derivative with maltooligosaccharide lactones. Combined evidence from dynamic light scattering (DLS), gel permeation chromatography (GPC), and transmission electron microscopy (TEM) indicates that they form small micelle-like nanoparticles (d congruent with 3 nm) in water. In the presence of Na2HPO4/NaH2PO4, nanoparticles are agglutinated with phosphate ions as a glue to grow in size up to 60-100 nm, as revealed by DLS as well as microscopy (TEM and AFM). The phosphate-induced agglutination processes can be followed by surface plasmon resonance (SPR). Amphiphile 2n is readily immobilized on the hydrophobized sensor chip of SPR to give a closely packed monolayer with oligosaccharide moieties exposed to bulk water. While there is no further adsorption of 2n on the resulting monolayer, this does occur when the latter is pretreated with the phosphate salts, ultimately giving rise to a multilayer upon repeated treatment of the chip with 2n and Na2HPO4/NaH2PO4 in an alternate manner. Kinetic analyses show that the phosphate-mediated inter(saccharide) interactions in terms of rate and affinity are markedly dependent on the oligosaccharide chain lengths (n), becoming more favorable with increasing n's. The novel aggregation and agglutination behaviors observed are discussed in terms of immobilizable and irreversible micelles on the basis of the cone-shaped structure of quadruple-chain amphiphile 2n having a huge saccharide pool and the efficiency of multiple hydrogen bonding therein. The unique intermolecular binding properties of compound 22 and analogues so far reported are reviewed in light of the present finding.

Probing polyvalency in artificial systems exhibiting molecular recognition

An approach to the study of polyvalency-the interaction of polyvalent receptors with polyvalent ligands-in unnatural systems is outlined. In this study, the complexation of dibenzylammonium cations by dibenzo[24]crown-8 or benzometaphenylene[25]crown-8 is utilized as the component receptor-ligand interaction. Two analogous multivalent receptors-each containing either seven dibenzo[24]crown-8 (DB24C8 CLUSTER) or seven benzometaphenylene[25]crown-8 (BMP25C8 CLUSTER) moieties appended to a modified beta-cyclodextrin core-were prepared in moderate yields. For each of these multivalent receptors, complementary mono- and divalent ligands containing one or two dialkylammonium centers, respectively, were prepared in good yields. These ligands contained fluorine atom substituents to allow their interactions with crown ether compounds to be probed by (19)F NMR spectroscopy. The complexation of these monovalent ligands with the DB24C8 CLUSTER and the BMP25C8 CLUSTER was studied by determining the average binding constant (K(AVE)) between the receptors and ligands. The abilities of the crown ether clusters to complex with these monovalent ligands was compared with those of the monovalent crown ethers dibenzo[24]crown-8 and benzometaphenylene[25]crown-8. In both instances, it was found that clustering seven crown ethers together into one molecule is detrimental to the abilities of the crown ether moieties to complex with monovalent dialkylammonium ligands. The complexation of the divalent ligands by the DB24C8 CLUSTER and the BMP25C8 CLUSTER was then studied-again by determining K(AVE)-and their abilities to complex with these ligands was compared with those of their respective component interactions. By determining K(AVE) for the polyvalent interaction, it was possible to calculate an association constant, K(POLY), for the binding of the divalent ligands by the DB24C8 CLUSTER and the BMP25C8 CLUSTER compounds. In both instances K(POLY) for the polyvalent interaction was found to be approximately 2 orders of magnitude higher than the association constants, K(A), for the component interaction.

Glycoside-clustering round calixarenes toward the development of multivalent ligands. Synthesis and conformational analysis of Calix[4]arene O- and C-glycoconjugates

Bis- and tetra-O- and C-glycosyl calixarenes (calixsugars) have been prepared by tethering carbohydrate moieties to a tetrapropoxycalix[4]arene scaffold through alkyl chains. Two methodologies have been employed. One consisted of the stereoselective multiple glycosylation of upper rim calix[4]arene polyols leading to calix-O-glycosides; the other involved a multiple Wittig olefination of upper rim calix[4]arene-derived polyaldehydes by the use of sugar phosphoranes and reduction of the alkene double bonds affording calix-C-glycosides. The NMR spectra and NOE experiments of bis-glycosylated products indicate that compounds bearing sugar-protected residues exist preferentially in solution in a flattened cone arrangement (far conformation) whereas deprotected derivatives adopt a close conformation. Calculations by molecular mechanics of the latter compounds point to a close conformation as well in gas phase.

Facile synthesis of 1-thio-beta-lactoside clusters scaffolded onto p-methoxyphenyl, beta-D-galactopyranoside, beta-D-glucopyranoside, and lactoside

The free-radical addition of 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl-(1-->4)-2,3,6-tri-O-acetyl-1-thio-beta-D-glucopyranose to the allyl ether functions of p-methoxyphenyl per-O-allyl-D-galactopyranoside, D-glucopyranoside, and lactoside provides a concise and effective route for synthesis of glycoside clusters, of use for exploring anti-metastatic activity.

Design and synthesis of glycodendrimers

Multivalent neoglycoconjugates with well-defined structures have considerable potential as inhibitors of cell surface protein-carbohydrate interactions and as tools for studying such recognition processes in vitro. In this review, we outline strategies and synthetic methods for making one such class of neoglycoconjugates based on dendrimers--the so-called glycodendrimers. Glycodendrimers can be classified as: (i) carbohydrate-coated; (ii) carbohydrate-centered; and (iii) fully carbohydrate-based. Approaches to their construction have included both the modification of commercially available dendrimers and de novo dendrimer synthesis. Examples from the authors' and other laboratories are drawn upon to illustrate design considerations and the application of dendritic synthetic principles--including divergent and convergent syntheses--for making glycodendrimers. Key coupling reactions for the synthesis of glycodendrimers include: amide and thiourea formation; glycosylation; photoaddition to allyl ethers; and reductive amination. The advantages and disadvantages of using protected and unprotected saccharide building blocks and potential applications for glycodendrimers in both biotechnology and materials science are also discussed.