Synthesis of the biologically active molecules: Trisaccharide Gal-Gal-Glu, a selectively protected precursor to D-eyrthrospingosine, and a library of PDI mimics

The synthesis of 6-(acryloylamino)-1-hexyl O-α- D-galactopyranosyl-(1 → 4)-O-β- D-galactopyranosyl-(1 → 4)-D-glucopyranoside was completed using the readily available and inexpensive starting materials, D-galactose and lactose. The overall yield for the synthesis was 14% with the longest linear sequence being 13 steps. The synthesis was amenable to large scale-ups because all the early intermediates could be purified by recrystalization. Ultimately, 0.5 g of our target molecule 1 was synthesized (chapter 1). The ample amount of 1 allowed for many biological assays to be performed. Compound 1 was co-polymerized with varying amounts of acrylamide to generate a water soluble polymers suitable to study multi-valent binding of the Gal-Gal-Glu trisaccharide to Shiga like toxin. The IC₅₀ of our polymers were measured to be 800–900 nM. The data shows a greater than 104 increase in binding versus the monomer. The enhancement was attributed to the ‘multi-valency effect’.; The synthesis of an orthogonally protected precusor to the lipid moiety of Gb₃, D-erythrosphingosine, was undertaken. D-erythrospingosine is a biologically active molecule that has a synthetically challenging ‘polar head’ portion where hydroxyl groups at C₁ and C₃ need to be differentially protected for eventual coupling reactions. Also a trans olefin needs to be installed between C₄ and C₅. Another challenge of the synthesis was to effectively install a trans olefin. The enantio-pure synthesis was completed in 11 steps from commercially available starting material in 39% yield.; The production of active therapeutic proteins is a challenging problem for both research labs and industry. The batch yields for the production of these proteins are usually low because of mismatched disulfide bonds, rendering the protein inactive. Many researchers ‘refold’ these mismatched proteins with protein disulfide isomerase (PDI) or small molecule alkyl thiols. We sought to improve on these processes by using aromatic thiols instead of their alkyl counterparts, allowing for the tuning of the thiol pK_a. We also sought to mimic the two thiols in the active site of PDI by covalently linking two aromatic thiols. The synthesis of a first generation aromatic thiol mimics of PDI is presented in chapter 3.