Two new series of pyrazolobenzothiazine-based carbothioamides (3a–o and 4a–o) were synthesized using saccharin as the starting material. The synthesized derivatives were investigated for their ability to inhibit monoamine oxidases (MAO). Compound 3b was found to be a very potent MAO-A inhibitor with an IC50 value of 0.003 ± 0.0007 μM, while compound 4d was the most effective inhibitor of MAO-B having an IC50 value of 0.02 ± 0.001 μM. Molecular docking studies were performed to identify the probable binding modes in the active site of the monoamine oxidase enzymes. The synthetic and computational investigations in the current work suggested that these newly identified inhibitors may serve as a powerful starting point for the exploration and optimization of potential therapeutic agents targeting Parkinson's disease.

Imidazole-1-sulfonyl azide and salts thereof are valuable reagents for diazo-transfer reactions, most particularly conversion of primary amines to azides. The parent reagent and its HCl salt present stability and detonation risks, but the hydrogen sulfate salt is significantly more stable. An updated procedure for the large-scale synthesis of this salt avoids isolation or concentration of the parent compound or HCl salt and will facilitate the use of hydrogen sulfate salt as the reagent of choice for diazo transfer.

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.

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).

D-Glucosamine derivatives bearing latent O4 functionality provide modified H/HS-type disaccharide donors for a final stage capping approach enabling introduction of conjugation-suitable, non-reducing terminal functionality to biologically important glycosaminoglycan oligosaccharides. Application to the synthesis of the first O4-terminus modified synthetic LMWH decasaccharide and an HS-like dodecasaccharide is reported.

Two series of fifteen N-substituted benzyl/phenyl-2-(3,4-dimethyl-5,5-dioxidopyrazolo[4,3-c][1,2]benzothiazin-2(4H)-yl)acetamides were screened for anti-HIV-1 activity and cytotoxicity. The compounds 6a, 6d, 6e, 6g and 6i from the series 6a–i of benzylamides and 7a, 7b, 7c, 7d and 7e from the series 7a–f of anilides were identified as effective anti-HIV-1 agents with EC50 values <20 μM. Among these compounds that displayed anti-HIV-1 activity, 6a, 6e, 6g and 6i showed no toxicity in human PBM, CEM and Vero cells, with the exception of 6a which displayed toxicity in Vero cells. Molecular docking of these compounds provided insight into the molecular mechanism and it was found that 6e, 6g and 6i bound deeply in the NNRTI binding pocket of the HIV-1 reverse transcriptase, using RT-bound nevirapine X-ray data and molecular docking for validation, showing the potential of these new structures as inhibitors of this viral enzyme.

A series of 1,4-disubstituted tetrazol-5-ones 3a, 5, 7, 12, 13 and 1,4-disubstituted tetrazol-5-thiones 3b, 9, 10 was synthesized and fully characterized by IR, MS, 1H NMR and 13C NMR. The series was evaluated for in vitro antibacterial activity against four Gram negative (Escherichia coli, Proteus mirabilis, Klebsiella pneumonia, and Pseudomonas aeruginosa) and three Gram positive (Staphylococcus aureus, Enterococcus faecalis, and Bacillus subtilis) bacteria. The zone of inhibition was measured using the well-diffusion assay, and in vitro minimum inhibitory concentration (MIC) was determined by microbroth dilution assay. MIC values indicate that compounds exhibited a varied range (0.2–37 μg/mL) of antibacterial activity against the tested bacterial strains. Statistically significant QSAR models were developed by the simple linear regression analysis for the correlation of MIC with computed descriptors. The concluded cross validated regression factors are 0.953 and 0.986 for E. coli, and S. aureus, respectively.

A series of aromatic and heteroaromatic primary amides were converted directly to carboxylic acids by heating with amyl nitrite in acetic acid. Most conversions proceeded to give reasonable to excellent yields on a range of substrates containing various functional groups. This reagent system is thus applicable for the direct hydrolysis of a range of different primary carboxamides. The reaction with a phenolic aromatic substrate afforded two alternative nitration products as major outcomes, evidencing alternative reaction pathways resulting from the free phenolic OH.

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.

A concise chemical synthesis of a series of structurally-defined heparin-like oligosaccharides is described. This work provides an efficient entry to octa-, deca-, and dodecasaccharides, including the first synthesis of (GlcNS6S-IdoA2S)5 and (GlcNS6S-IdoA2S)6. Evaluation of the in vitro activity of these species against FGF2- and VEGF165-dependent endothelial cell proliferation and migration establishes that octa- and decasaccharides are more potent in targeting FGF2-induced effects, where cell migration is affected more significantly than proliferation. These structure–activity relationships exemplify the significance of 6-O-sulfation in regulating the activity of angiogenic growth factors.

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.

•Preparation and solid state study of a novel member of an interesting structural class.•This modeling studies show that the E-isomer is the global minimum isomer.•A rationale for the observed E-selectivity is based on strong E–E dimerization.An efficient synthesis of the novel (E)-N′-(1-p-tolylethylidene)furan-2-carbohydrazide is described. The molecular structural features were then confirmed by single crystal X-ray diffraction. Quantum chemical calculations including molecular geometry, intermolecular H-bonds, and vibrational frequencies were carried out for the structures to explain stability and geometry using both density functional (DFT/B3LYP) and the Hartree–Fock (HF) with 6-311+G(d,p) basis set. The calculated structural parameters are presented and compared with their experimental X-ray counterparts. The E-isomer is a global minimum on the potential energy surface. However, validation of the computational methods here via comparison with the observed X-ray data enabled computational analysis to predict that head-to-tail E/E-dimer of the observed E-isomer has significantly stronger intermolecular hydrogen bonding compared with the non-observed Z/Z-dimer. It was observed that the stretching mode of NH and CO shifted to lower frequencies, due to pairwise intermolecular NH⋯O hydrogen bonds. This provides a clear rationale for the isomeric specificity obtained and provides a validation of the optimized method which could be applied to predict structures of other useful carbohydrazides. Generally, it has been concluded that the findings of B3LYP hybrid functional fit better to the observed geometrical and vibrational parameters than the results of the HF.

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 1C4 conformations in solution, the iduronate ester adopts the 4C1 conformation in solid state. An X-ray structure is also reported for the novel, 4C1-conformationally locked bicyclic 1,6-anhydro iduronate lactone along with an X-ray structures of a novel distorted 4C1 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.

Divergent synthesis of two novel C-glycosidic multivalent mannosides derived from a common trivalent C-mannosyl carboxylate-terminated intermediate is described. This illustrates synthesis of multivalent C-glycosidic architectures bearing variable extended functionalized tethers. One such tether incorporates an embedded fluorescent unit providing a C-mannosyl multivalent epitope offering potential applications through further conjugation or immobilization.Synthesis of novel trivalent α-C-mannosides bearing different end-functionalized tethers is described.

A modular approach to the synthesis of trivalent C-glycosidic carbohydrates is described. The approach is illustrated employing carboxylate-terminated C-glycosidic d-mannose, d-glucose, and d-galactose derivatives with different length C1-linked spacer units and also core units with different length linker units attached. The central core scaffold is additionally functionalized via a succinamide-based, conjugatable linker unit, exemplified in an extended multivalent derivative [31] and a pyrene-bearing fluorsecent-labeled tris-C-mannosyl conjugate [33].

The autoinducer (4S)-4,5-dihydroxypentane-2,3-dione ((S)-DPD, AI-2) facilitates chemical communication, termed ‘quorum sensing’, amongst a wide range of bacteria, The synthesis of (S)-DPD is challenging in part due to its instability. Herein we report a novel synthesis of (S)-DPD via (2S)-2,3-O-isopropylidene glyceraldehyde, through Wittig, dihydroxylation and oxidation reactions, with a complimentary asymmetric synthesis to a key precursor. Its enantiomer (R)-DPD, was prepared from d-mannitol via (2R)-2,3-O-isopropylideneglyceraldehyde. The synthesized enantiomers of DPD have AI-2 bioluminescence-inducing properties in the Vibrio harveyi BB170 strain.Synthesis of both enantiomers of autoinducer DPD (shown (S), R = H) along with their ester bioprecursors (R = Bz, Ac) & biological assays.

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.

•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.Figure optionsDownload full-size imageDownload as PowerPoint slide

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).

D-Glucosamine derivatives bearing latent O4 functionality provide modified H/HS-type disaccharide donors for a final stage capping approach enabling introduction of conjugation-suitable, non-reducing terminal functionality to biologically important glycosaminoglycan oligosaccharides. Application to the synthesis of the first O4-terminus modified synthetic LMWH decasaccharide and an HS-like dodecasaccharide is reported.

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.

A concise chemical synthesis of a series of structurally-defined heparin-like oligosaccharides is described. This work provides an efficient entry to octa-, deca-, and dodecasaccharides, including the first synthesis of (GlcNS6S-IdoA2S)5 and (GlcNS6S-IdoA2S)6. Evaluation of the in vitro activity of these species against FGF2- and VEGF165-dependent endothelial cell proliferation and migration establishes that octa- and decasaccharides are more potent in targeting FGF2-induced effects, where cell migration is affected more significantly than proliferation. These structure–activity relationships exemplify the significance of 6-O-sulfation in regulating the activity of angiogenic growth factors.