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The efficient synthesis of oligosaccharides is becoming increasingly important as their roles in biological recognition and signalling mechanisms are exploited as potential therapeutic agents. Carbohydrate processing enzymes are desirable catalysts for creating oligosaccharides as the use of multi-step chemical syntheses are avoided; however, they do not always meet exact experimental requirements.

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In this thesis four projects related to bioactive carbohydrates are described. The first project is about the extraction of iminosugars from Hyacinthoides non-scripta. This is the first time that extraction from English bluebell seeds has been described. Efficient extraction and isolation methods are reported. Another project discusses the development of a total synthetic carbohydrate conjugate vaccine candidate against Streptococcus pneumoniae type 14 using Gold nanoparticles as carrier. The synthetic pathway of the introduction of a linker for conjugation, and the deprotection of the tetrasaccharide corresponding to the repeating unit of the Streptococcus pneumoniae type 14 capsular polysaccharide is described. The biological results of the developed vaccine candidate are briefly discussed. In the third project, attempts to synthesise regioselectively sulfated disaccharides to be used in binding studies with FedF adhesin of E. coli are described. In this section, an improved high-yielding method based on the Heyns rearrangement for the synthesis of N-acetyl lactosamine (LacNAc) is also reported. In the fourth part, conjugation of the Lewis b hexasaccharide to be used for studies of Lewis b blood group antigen binding adhesin is reported.

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A new metal-based method to synthesize C(1)-substituted glycals has been developed. Starting with the obtained substituted C-glycals, the possibility of a stereocontrolled addition (via azidoselenation) to form β-C-substituted-2-aminoglycosides has been investigated. Instead of forming the expected C-glycosyl derivatives of 2-amino sugars, an inseparable mixture of diastereomers, which were derived from the corresponding C(1)-allylated glycals, has been obtained.

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Carbohydrate-carbohydrate interactions (CCIs) have been shown to be an important interaction in molecular recognition. These interactions present characteristics such as the synergistic effect with other interactions e.g. protein-protein interactions, specificity, polyvalency and in some cases requirement of divalent cations. CCIs remain insufficiently documented due to the weakness of such an interaction, which is difficult to probe by classical techniques and study at the molecular level in a monovalent system has not been performed. In order to study the CCI, a peptide based on alanine and lysine has been designed. Carbohydrates have been ligated to this peptide and changes in a-helix and random coil conformations are examined using CD spectroscopy. This system was shown to function as a reporter for CCls through changes in the conformations of the peptide. A second system that will be employed to study eCls is utilising the thiol-thioester exchange reaction. This involves a reaction between a carbohydrate with a thioester linkage and a carbohydrate linked to a thiol moiety. The resulting equilibrium is to be probed using HPLC. Synthetic routes have been developed in order to obtain the desired thiols and thioester. First studies showed that a CHO-π interaction can be quantified using this system. The carbohydrates to be attached are: Lex, sLex, LeY. The synthesis of Lex has been improved within the Gallagher group. A new synthesis of LeY was performed using an armed/disarmed strategy. Meanwhile, studies towards the synthesis of sLex were carried out.

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