Synthesis of O-linked Carbasugar Analogues of Galactofuranosides and N-linked Neodisaccharides

In this thesis, carbohydrate mimicry is investigated through the syntheses of carbohydrate analogues and evaluation of their inhibitory effects on carbohydrate-processing enzymes. Galactofuranosides are interesting structures because they are common motifs in pathogenic microorganisms but not found in mammals. M.tuberculosis, responsible for the disease tuberculosis, has a cell wall containing a repeating unit of alternating (1→5)- and (1→6)-linked β-D-galactofuranosyl residues. Synthetic inhibitors of the enzymes involved in the biosynthesis of the cell wall could find great therapeutic use. The first part of this thesis describes the first synthesis of the hydrolytically stable carbasugar analogue of galactofuranose, 4a-carba-β-D-Galf, and the synthetic work of synthesising β-linked pseudodisaccharides containing carba-Galf, which were tested for glycosyltransferease inhibitory activity. The pseudodisaccharide carba-Galf-(β1→5)-carba-Galf was found to be a moderate inhibitor of the glycosyltransferase GlfT2 of M.tuberculosis. The thesis also describes how a general method towards biologically relevant α-linked carba-Galf ethers was developed. The final part of this thesis is focussed on the formation of nitrogen-linked monosaccharides without the participation of the anomeric centre. Such a mode of coupling is called tail-to-tail neodisaccharide formation. The couplings of carbohydrate derivatives via the Mitsunobu reaction are successfully reported herein. The method describes the key introduction of an allylic alcohol in the electrophile and the subsequent functionalisation of the alkene to obtain the neodisaccharide. Two synthesised neodisaccharides presented in this thesis have been sent to be tested for glycosidase inhibitory activity.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript

Carbasugar analogues of galactofuranosides: α-O-linked derivatives

Using an indirect method, we have synthesised α-linked carbasugar analogues of galactofuranosides for the first time. Ring opening of a β-talo configured carbasugar 1,2-epoxide by alcohol nucleophiles under Lewis acidic conditions proceeded with very good regioselectivity to give α-talo configured C1-substituted ethers with a free OH-group at the C2 position. Inversion of configuration at C2 by an oxidation–reduction sequence gave the α-galacto configured carbahexofuranose C1 ethers. A carbadisaccharide corresponding to the Galf(α1→3)Manp substructure from Apodus deciduus galactomannan was synthesised to exemplify the method

Bioluminescence imaging of small biomolecules

The invention relates to a technique to detect small molecules using Bioluminescence imaging (BLI) to image and quantify non-invasively, in vitro and in vivo,intracellular metabolite fluxes and which can be applied to azido-modified compounds, such as azido-modified biomolecules

⁶⁸Ga-Labeled Gold Glyconanoparticles for Exploring Blood–Brain Barrier Permeability: Preparation, Biodistribution Studies, and Improved Brain Uptake via Neuropeptide Conjugation

New tools and techniques to improve brain visualization and assess drug permeability across the blood–brain barrier (BBB) are critically needed. Positron emission tomography (PET) is a highly sensitive, noninvasive technique that allows the evaluation of the BBB permeability under normal and disease-state conditions. In this work, we have developed the synthesis of novel water-soluble and biocompatible glucose-coated gold nanoparticles (GNPs) carrying BBB-permeable neuropeptides and a chelator of the positron emitter ⁶⁸Ga as a PET reporter for in vivo tracking biodistribution. The small GNPs (2 nm) are stabilized and solubilized by a glucose conjugate. A NOTA ligand is the chelating agent for the ⁶⁸Ga, and two related opioid peptides are used as targeting ligands for improving BBB crossing. The radioactive labeling of the GNPs is completed in 30 min at 70 °C followed by purification via centrifugal filtration. As a proof of principle, a biodistribution study in rats is performed for the different ⁶⁸Ga-GNPs. The accumulation of radioactivity in different organs after intravenous administration is measured by whole body PET imaging and gamma counter measurements of selected organs. The biodistribution of the ⁶⁸Ga-GNPs varies depending on the ligands, as GNPs with the same gold core size show different distribution profiles. One of the targeted ⁶⁸Ga-GNPs improves BBB crossing near 3-fold (0.020 ± 0.0050% ID/g) compared to nontargeted GNPs (0.0073 ± 0.0024% ID/g) as measured by dissection and tissue counting

Amine-linked diglycosides: Synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibition assays

Diglycose derivatives, consisting of two monosaccharides linked at non-anomeric positions by a bridging nitrogen atom, have been synthesised. Conversion of one of the precursor monosaccharide coupling components into an unsaturated derivative enhances its electrophilicity at the allylic position, facilitating coupling reactions. Mitsunobu coupling between nosylamides and 2,3-unsaturated-4-alcohols gave the 4-amino-pseudodisaccharides with inversion of configuration as single regio- and diastereoisomers. A palladium-catalysed coupling between an amine and a 2,3-unsaturated 4-trichloroacetimidate gave a 2-amino-pseudodisaccharide as the major product, along with other minor products. Derivatisation of the C=C double bond in pseudodisaccharides allowed the formation of Man(N4–6)Glc and Man(N4–6)Man diglycosides. The amine-linked diglycosides were found to show weak glycosidase inhibitory activity

Cyclotron-based production of 68Ga, [68Ga]GaCl3, and [68Ga]Ga-PSMA-11 from a liquid target

Abstract Purpose To optimize the direct production of 68Ga on a cyclotron, via the 68Zn(p,n)68Ga reaction using a liquid cyclotron target. We Investigated the yield of cyclotron-produced 68Ga, extraction of [68Ga]GaCl3 and subsequent [68Ga]Ga-PSMA-11 labeling using an automated synthesis module. Methods Irradiations of a 1.0 M solution of [68Zn]Zn(NO3)2 in dilute (0.2–0.3 M) HNO3 were conducted using GE PETtrace cyclotrons and GE 68Ga liquid targets. The proton beam energy was degraded to a nominal 14.3 MeV to minimize the co-production of 67Ga through the 68Zn(p,2n)67Ga reaction without unduly compromising 68Ga yields. We also evaluated the effects of varying beam times (50–75 min) and beam currents (27–40 μA). Crude 68Ga production was measured. The extraction of [68Ga]GaCl3 was performed using a 2 column solid phase method on the GE FASTlab Developer platform. Extracted [68Ga]GaCl3 was used to label [68Ga]Ga-PSMA-11 that was intended for clinical use. Results The decay corrected yield of 68Ga at EOB was typically > 3.7 GBq (100 mCi) for a 60 min beam, with irradiations of [68Zn]Zn(NO3)2 at 0.3 M HNO3. Target/chemistry performance was more consistent when compared with 0.2 M HNO3. Radionuclidic purity of 68Ga was typically > 99.8% at EOB and met the requirements specified in the European Pharmacopoeia ( 50% (~ 1.85 GBq, 50 mCi); yields improved as processes were optimized. Labeling yields for [68Ga]Ga-PSMA-11 were near quantitative (~ 1.67 GBq, 45 mCi) at EOS. Cyclotron produced [68Ga]Ga-PSMA-11 underwent full quality control, stability and sterility testing, and was implemented for human use at the University of Michigan as an Investigational New Drug through the US FDA and also at the Royal Prince Alfred Hospital (RPA). Conclusion Direct cyclotron irradiation of a liquid target provides clinically relevant quantities of [68Ga]Ga-PSMA-11 and is a viable alternative to traditional 68Ge/68Ga generators.http://deepblue.lib.umich.edu/bitstream/2027.42/174048/1/41181_2020_Article_106.pd