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L-Idofuranoside cyanohydrin 1 is converted on large scale into a mixture of L-IdoA methyl pyranosides and furanosides, which is converged to provide short 2-step routes to bicyclic [3.2.1] or [2.2.2] L-iduronate lactones. The former is obtained via a 100 g scale synthesis of 3-OBn L-IdoA. A two-step conversion of this mixture provides either pure anomer of the novel [2.2.2] l-iduronate thioglycoside lactones. Both [3.2.1] and [2.2.2] lactones are converted into GlcN-IdoA heparin precursor disaccharides. The [2.2.2] lactone enables a scalable 3-step route from 1 to a new type of highly disarmed O-4 iduronate thioglycoside, which is an effective acceptor with glucoazide thioglycoside donors. The resulting new iduronic [2.2.2] lactone disaccharides are readily rearmed by mild methanolysis to provide GlcN-IdoA thiophenyl disaccharide donors, intercepting their established utility for the assembly of both heparin- and heparan sulfate-like oligosaccharides. The [2.2.2] lactonization acts as a conformational switch to superdisarm iduronate components, reversible by lactone ring opening. In addition, the separated 2,4-diacetates also provide short access to all four anomeric and ring size isomers of l-iduronic acid methyl glycosides, including the first syntheses of the parent idofuranosides. X-ray structures are reported for a [2.2.2] iduronate lactone and examples of both methyl L-idopyranoside and novel methyl-L-idofuranoside systems.

The chemical synthesis of long oligosaccharides remains a major challenge. In particular, the synthesis of glycosaminoglycan (GAG) oligosaccharides belonging to the heparin and heparan sulfate (H/HS) family has been a high profile target, particularly with respect to the longer heparanome. Herein we describe a synthesis of the longest heparin-related oligosaccharide to date and concurrently provide an entry to the longest synthetic oligosaccharides of any type yet reported. Specifically, the iterative construction of a series of [4]n-mer heparin-backbone oligosaccharides ranging from 16-mer through to the 40-mer in length is described. This demonstrates for the first time the viability of generating long sequence heparanoids by chemical synthesis, via practical solution-phase synthesis. Pure-Shift HSQC NMR provides a dramatic improvement in anomeric signal resolution, allowing full resolution of all 12 anomeric protons and extrapolation to support anomeric integrity of the longer species. A chemically pure 6-O-desfulfated GlcNS-IdoAS icosasaccharide (20-mer) represents the longest pure synthetic heparin-like oligosaccharide.

Angiogenesis has emerged as a novel target for anti-cancer therapies through randomized clinical trials that tested the benefit of adding vascular endothelial growth factor (VEGF) inhibitors to conventional cytotoxic therapies. However, despite improvements in the progression-free survival, the benefit in overall survival is modest. Tumour angiogenesis is regulated by a number of angiogenic cytokines. Thus innate or acquired resistance to VEGF inhibitors can be caused, at least in part, through expression of other angiogenic cytokines, including fibroblast growth factor 2 (FGF2), interleukin 8 (IL-8) and stromal-cell-derived factor 1α (SDF-1α), which make tumours insensitive to VEGF signalling pathway inhibition. The majority of angiogenic cytokines, including VEGF-A, FGF2, IL-8 and SDF-1α, manifest an obligate dependence on heparan sulfate (HS) for their biological activity. This mandatory requirement of angiogenic cytokines for HS identifies HS as a potential target for novel anti-angiogenic therapy. Targeting multiple angiogenic cytokines with HS mimetics may represent an opportunity to inhibit tumour angiogenesis more efficiently. Our published studies and unpublished work have demonstrated the feasibility of generating synthetic HS fragments of defined structure with biological activity against a number of angiogenic cytokines.

Adhesamine is an organic small molecule that promotes adhesion and growth of cultured human cells by binding selectively to heparan sulfate on the cell surface. The present study combined chemical, physicochemical, and cell biological experiments, using adhesamine and its analogues, to examine the mechanism by which this dumbbell-shaped, non-peptidic molecule induces physiologically relevant cell adhesion. The results suggest that multiple adhesamine molecules cooperatively bind to heparan sulfate and induce its assembly, promoting clustering of heparan sulfate-bound syndecan-4 on the cell surface. A pilot study showed that adhesamine improved the viability and attachment of transplanted cells in mice. Further studies of adhesamine and other small molecules could lead to the design of assembly-inducing molecules for use in cell biology and cell therapy.

The multigram-scale synthesis of a sulfation-site programmed heparin-like dodecasaccharide is described. Evaluation alongside dodecasaccharides lacking this single glucosamine O6-sulfation, or having per-O6-sulfation, shows that site-specific modification of the terminal glucosamine dramatically interconverts regulation of in vitro and in vivo biology mediated by the two important chemokines, CXCL12 (SDF1α) or CXCL8 (IL-8).

Graphical abstract, Highlights • Synthesis of a matrix of sulfation-programmed GlcN–IdoA disaccharides. • Demonstrates effective synthesis using various GlcN donors and Ido acceptor. • Four homogeneous sulfation-varied heparin disaccharides used to obtain Raman and Raman ROA data. • Spectra provide indicative comparisons of signature sulfation bands for differing sulfation levels. • Data are used to provide comparisons/differences to native heparin spectra., Synthesis of an array of differentially sulfated GlcN–IdoA disaccharides, accessible on good scale, directly from l-iduronate components is described. These are specifically directed to provide the sulfation variability at the key most common biologically relevant sulfation-variable l-IdoA O-2 and d-GlcN O-6 and amino sites of this heparin disaccharide. This sulfation-varied matrix has allowed the first evaluation of using Raman/ROA spectroscopy to characterize changes in spectra as a function of both site and level of sulfation with pure, defined heparin-related disaccharide species. This provides analysis of both similarities and differences to digest native heparin and this shows evidence of different types of changes in conformations and conformational freedom as a function of some specific sulfation changes at the disaccharide level. It is anticipated that this data set will open the way for applications to further site-specific sulfated saccharides and demonstrates the capability offered by Raman–ROA towards fingerprinting sulfation in heparin fragments.

The first example of a gram-scale synthesis of a structurally defined, heparin-related dodecasaccharide is reported. An iterative 14-step process using an iduronate donor disaccharide delivers >1g quantities of the dodecasaccharide sequence [GlcNS-IdoA2S](6)-OMe in 15% overall yield from the reducing terminal disaccharide, a 2 orders of magnitude increase in scale for access to synthetic heparanoid dodecasaccharide mimetics. The synthesis also delivers multigram amounts of the protected oligosaccharides from tetra- through to dodecasaccharide.

Heparin-like oligosaccharides mediate numerous important biological interactions, of which many are implicated in various diseases. Synthetic improvements are central to the development of such oligosaccharides as therapeutics and, in addition, there are no methods to elucidate the pharmacokinetics of structurally defined heparin-like oligosaccharides. Here we report an efficient two-cycle [4+4+4] tetrasaccharide-iteration-based approach for rapid chemical synthesis of a structurally defined heparin-related dodecasaccharide, combined with the incorporation of a latent aldehyde tag, unmasked in the final step of chemical synthesis, providing a generic end group for labelling/conjugation. We exploit this latent aldehyde tag for 3H radiolabelling to provide the first example of this kind of agent for monitoring in vivo tissue distribution and in vivo stability of a biologically active, structurally defined heparin related dodecasaccharide. Such studies are critical for the development of related saccharide therapeutics, and the data here establish that a biologically active, synthetic, heparin-like dodecasaccharide provides good organ distribution, and serum lifetimes relevant to developing future oligosaccharide therapeutics., Heparin-like oligosaccharides are implicated in various diseases. Hansen et al. report an efficient two-cycle [4+4+4] tetrasaccharide-iteration-based approach to synthesize a structurally defined heparin dodecasaccharide with a latent aldehyde tag for labelling and conjugation.

A diastereomerically pure cyanohydrin, preparable on kilogram scale, is efficiently converted in one step into a novel L-iduronamide. A new regioselective acylation of this iduronamide and a new mild amide hydrolysis method mediated by amyl nitrite enables short, scalable syntheses of an L-iduronate diacetate C-4 acceptor, and also L-iduronate C-4 acceptor thioglycosides. Efficient conversions of these to a range of heparin-related gluco-ido disaccharide building blocks (various C-4 protection options) including efficient multigram access to key heparin-building block ido-thioglycoside donors are described. A 1-OAc disaccharide is converted into a heparin-related tetrasaccharide, via divergence to both acceptor and donor disaccharides. X-ray and NMR data of the 1,2-diacetyl iduronate methyl ester and the analogous iduronamide show that while both adopt (1)C(4) conformations in solution, the iduronate ester adopts the (4)C(1) conformation in solid state. An X-ray structure is also reported for the novel, (4)C(1)-conformationally locked bicyclic 1,6-anhydro iduronate lactone along with an X-ray structures of a novel distorted (4)C(1) iduronate 4,6-lactone. Deuterium labeling also provides mechanistic insight into the formation of lactone products during the novel amyl nitrite-mediated hydrolysis of iduronamide into the parent iduronic acid functionality.

The pyranose ring of L-iduronic acid (IdoA), a major constituent of the anticoagulant heparin, is an equilibrium of multiple ring puckers that have evaded quantification by experiment or computation. In order to resolve this enigma, we have calculated the free energy landscape of IdoA and two related monosaccharides from extensive microsecond simulations. After establishing that the simulated puckers had reached equilibrium, hypotheses were confirmed that (a) IdoA (1)C(4)- and (4)C(1)-chair conformations exchange on the microsecond time scale, (b) C5 epimerization leads to a (4)C(1)-chair, and (c) IdoA 2-O-sulfation (IdoA2S) stabilizes the (1)C(4) conformer. The IdoA and IdoA2S (1)C(4) conformers were isoenergetic and computed to be 0.9 and 2.6 kcal mol(-1) lower in free energy than their respective (4)C(1)-chair conformations. The simulations also predicted that the IdoA (2)S(O)-skew-boat was less populated than previously thought. Novel chemical synthesis and ultra-high-field NMR supported these observations, but slight discrepancies in observed and predicted NMR vicinal couplings implied that the simulation overestimated the population of the IdoA (4)C(1)-chair with respect to (1)C(4)-chair due to small force field inaccuracies that only manifest in long simulations. These free-energy calculations drive improvements in computational methods and provide a novel route to carbohydrate mimetic biomaterials and pharmaceuticals.

l-Ido cyanohydrin 3 was prepared from diacetone-d-glucose in four steps and 76% overall yield and 90% de via cyanohydrin reaction of aldehyde 2. This process can be scaled to provide >1 mol of pure l-ido cyanohydrin 3. Cyanohydrin 3 was elaborated to 1,2-isopropylidine-protected l-ido nitrile (8), iduronic amide 9, and known carboxy ester 10. Coupling of 8 and 9 with glucosamine donors leads to new types (6-cyano and 6-carboxamide) of heparin-related disaccharides.

Angiogenesis has been validated as a target in multiple randomised trials in ovarian cancer, in which addition of VEGF pathway inhibitors to conventional cytotoxic treatment resulted in increased progression-free and in some trials overall survival. However, the benefit from VEGF pathway inhibitors is still modest and the redundancy of angiogenic cytokines might be one of the underlying mechanisms. The majority of angiogenic cytokines, such as FGFs, HGF, VEGF165, IL-8, SDF-1α, HB-EGF that are also linked to ovarian cancer, critically depend on the linear glycosaminoglycan, heparan sulfate (HS), for their biological activity. HS is composed of repeating disaccharides that consist of N-substituted glucosamine and a hexuronic acid residue and is bound to core proteins which support signaling complex formation. The critical importance of glucosamine-6-O-sulfate (6S) moieties in assembling the growth factor/receptor signaling complex implies that reduced 6S content in HS will impact angiogenesis and thereby tumor growth. We used chemical synthesis to produce three differentially sulfated dodecasaccharides (12-mers). All three 12-mers were homogeneously sulfated at the 2-O position of iduronate (IS) and the N-position of glucosamine (NS). The first 12-mer lacked 6S moieties ([NSIS]6), the second 12-mer had a single 6S introduced at the non-reducing end of the molecule ([NS6SIS]1-[NSIS]5) and the third 12-mer was uniformly 6-O-sulfated ([NS6SIS]6). Comparison of anti-angiogenic properties of these 12-mers revealed differential inhibitory activities against angiogenic cytokines. While a single 6S at the non-reducing end slightly improved inhibition of FGF2- and VEGF165-induced angiogenic responses when compared to non-6S-sulfated 12-mer, it produced striking changes in the biological effects on IL-8/SDF-1α. Addition of one 6S abolished inhibitory activity of [NSIS]6 against IL-8, but conferred superior activity in inhibition of SDF-1α, in vitro and in vivo. These dramatic differential effects were absent if all glucosamine residues were 6-O-sulfated. NSIS 12-mer with a single 6S inhibited FGF-2-dependent microvessel formation in tumor xenografts, FGFR signaling in tumor blood vessels, but was insufficient in inhibiting tumor growth, most likely due to the dominant role of VEGF. We demonstrate unique structure-activity relationships for inhibition of SDF-1α and IL-8 which opens new opportunities in the development of glycotherapeutics. We show that oligosaccharides can be designed to target multiple or specific angiogenic cytokines, thus demonstrating the feasibility in generating agents that overcome resistance to VEGF inhibitors. Citation Format: Gordon C. Jayson, Steen U. Hansen, Gavin J. Miller, Claire Cole, Graham Rushton, John M. Gardiner, Egle Avizienyte. Development of synthetic heparan sulfate oligosaccharides as anti-angiogenic agents. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1375. doi:10.1158/1538-7445.AM2015-1375

Heparan sulfate (HS), a linear glycosaminoglycan, is an essential structural component required for the activity of numerous angiogenic cytokine-receptor signalling complexes. To exploit the potential of inhibiting HS-dependent signalling complexes we synthesized a series of heparan sulfate oligosaccharides containing up to 12 saccharide residues with variable but defined sulfation patterns. The ability of oligosaccharides to compete with HS in FGF2, VEGF and IL-8 binding significantly increased with the length of oligosaccharides and especially with additional sulfate groups incorporated at specific positions in the hexuronic acid and glucosamine. In this competition assay, oligosaccharides exhibited higher levels of inhibition of FGF2 binding to HS than of VEGF and IL-8 binding to HS. Correspondingly, the inhibitory potential of oligosaccharides against FGF2-, VEGF- and IL-8-mediated endothelial cell responses was greater in longer species of oligosaccharides that bore more sulfate residues. Oligosaccharides inhibited cytokine-induced endothelial cell migration to the same extent as kinase inhibitors targeting FGF receptors or VEGF receptor 2 (VEGFR2). In contrast, FGF2-induced endothelial cell proliferation was only inhibited when cells were treated with an oligosaccharide composed of 12 saccharide residues at a concentration that significantly exceeded that of the FGFR inhibitor suggesting that oligosaccharides mainly interfere with the migration, but not proliferation of endothelial cells. The ability of oligosaccharides to target endothelial cell migration correlated with their ability to ablate FGF2- or VEGF-induced accumulation of activated peripheral FAK-pY397 and actin polymerization at the cell periphery. More importantly, there was a strong correlation between oligosaccharide structure and the level of inhibition of endothelial tube formation. Correlating with the biological activity of oligosaccharides, FGF2- and VEGF-induced downstream signalling events were sensitive to the treatment with biologically active oligosaccharides that specifically reduced FRS2, VEGFR2, ERK1/2 and AKT phosphorylation. In conclusion, we have determined the critical number of HS saccharide residues and sulfation pattern required to inhibit endothelial cell responses to key angiogenic cytokines. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1374.

Background Heparan sulfate (HS) is an important regulator of the assembly and activity of various angiogenic signalling complexes. However, the significance of precisely defined HS structures in regulating cytokine-dependent angiogenic cellular functions and signalling through receptors regulating angiogenic responses remains unclear. Understanding such structure-activity relationships is important for the rational design of HS fragments that inhibit HS-dependent angiogenic signalling complexes. Methodology/Principal Findings We synthesized a series of HS oligosaccharides ranging from 7 to 12 saccharide residues that contained a repeating disaccharide unit consisting of iduronate 2-O-sulfate linked to glucosamine with or without N-sulfate. The ability of oligosaccharides to compete with HS for FGF2 and VEGF165 binding significantly increased with oligosaccharide length and sulfation. Correspondingly, the inhibitory potential of oligosaccharides against FGF2- and VEGF165-induced endothelial cell responses was greater in longer oligosaccharide species that were comprised of disaccharides bearing both 2-O- and N-sulfation (2SNS). FGF2- and VEGF165-induced endothelial cell migration were inhibited by longer 2SNS oligosaccharide species with 2SNS dodecasaccharide activity being comparable to that of receptor tyrosine kinase inhibitors targeting FGFR or VEGFR-2. Moreover, the 2SNS dodecasaccharide ablated FGF2- or VEGF165-induced phosphorylation of FAK and assembly of F-actin in peripheral lamellipodia-like structures. In contrast, FGF2-induced endothelial cell proliferation was only moderately inhibited by longer 2SNS oligosaccharides. Inhibition of FGF2- and VEGF165-dependent endothelial tube formation strongly correlated with oligosaccharide length and sulfation with 10-mer and 12-mer 2SNS oligosaccharides being the most potent species. FGF2- and VEGF165-induced activation of MAPK pathway was inhibited by biologically active oligosaccharides correlating with the specific phosphorylation events in FRS2 and VEGFR-2, respectively. Conclusion/Significance These results demonstrate structure-function relationships for synthetic HS saccharides that suppress endothelial cell migration, tube formation and signalling induced by key angiogenic cytokines.