Studies directed toward the total synthesis of longifolene

This thesis describes studies directed toward the total synthesis of longifolene utilizing as a key step an intramolecular Diels-Alder cyclization. Different approaches for the construction of spiro[2.4]hepta-4,6-dienes have been explored and a general route involving the fulvene 63 developed. Nucleophilic addition of methlylithium to this fulvene generates a cyclopentadiene anion in situ, which closes to the requisite cyclopropane system by epoxide ring opening to afford 65. This cyclopentadiene unit will thus serve as the 'left-had portion' for the approach to longifolene which is outlined. Procedures for the preparation and introduction of a suitable 'right-hand portion' have also been examined, these preliminary results have indicated the subtle blend of functionality and reactivity that will be required to generate the dienophilic unit. A suitable triene system 104 was synthesized (unfortunately in low yield) but under the conditions examined the desired Diels-Alder cyclization did not occur

Phenylenediamine-based bivalent glycocyclophanes : synthesis and analysis of the influence of scaffold rigidity and ligand spacing on lectin binding in cell systems with different glycomic profiles

The conjugation of carbohydrates to synthetic scaffolds has the goal of preparing potent inhibitors of lectin binding. We herein report the synthesis of a panel of bivalent compounds (cyclophane and terephthalamide-derivatives) then used to establish the influence of scaffold flexibility on respective inhibitory potency in a medically relevant test system. Synthetic routes to two phenylenediamine-based glycocyclophanes involving Ugi reactions of glucuronic acid derivatives and subsequent ring closing metathesis are described, as are improvements for producing terephthalamide-based carbohydrate carriers. Assays were performed with human tumour cells measuring quantitatively the influence of the test compounds on fluorescent surface staining by labelled lectins. Biological evaluation using two different lines of cancer cells as well as cells with known alterations in the glycomic profile (cells treated with an inhibitor of glycan processing and a glycosylation mutant) reduced the risk of generating premature generalizations regarding inhibitor potency. Bioactivity relative to free mannose was invariably determined for the synthetic compounds. A clear trend for enhanced inhibitory properties for macrocyclic compounds compared to non-macrocyclic derivatives was discerned for one type of glycocyclophane. Herein we also document the impact of altering the spacing between the mannose residues, altering cell surface ligand density and cell-type reactivity. The applied strategy for the cell assays is proposed to be of general importance in the quest to identify medically relevant lectin inhibitors