Carbohydrates play major roles in many biological processes. Therefore, the synthesis of oligosaccharides is of considerable interest for biological, medicinal, and pharmacological studies. Many approaches have been developed for the synthesis of oligosaccharides, in which the main focus is often the formation of the glycosidic bonds. Traditional approaches use protecting group strategies that can be time consuming and can result in poor overall yield. This thesis describes the protecting group-free synthesis of a series of glycosyl donors of a range of mono- and disaccharides. These donors can be used to synthesize unprotected glycosyl chlorides, observed in situ. Reaction of the glycosyl chlorides with a variety of nucleophiles afforded the expected displacement products, giving access to a range of O-, N-, and S-linked glycosides, without resorting to the use of protecting groups.

Carbohydrates play major roles in many biological processes. Therefore, the synthesis of oligosaccharides is of considerable interest for biological, medicinal, and pharmacological studies. Many approaches have been developed for the synthesis of oligosaccharides, in which the main focus is often the formation of the glycosidic bonds. Traditional approaches use protecting group strategies that can be time consuming and can result in poor overall yield. This thesis describes the protecting group-free synthesis of a series of glycosyl donors of a range of mono- and disaccharides. These donors can be used to synthesize unprotected glycosyl chlorides, observed in situ. Reaction of the glycosyl chlorides with a variety of nucleophiles afforded the expected displacement products, giving access to a range of O-, N-, and S-linked glycosides, without resorting to the use of protecting groups.

In 1908, H. Emil Fisher attempted to prepare glycinal, an unprotected amino aldehyde, which he found to be inherently unstable and prone to polymerization. This instability arises from the propensity of amines to condense with aldehydes. Accordingly, amino aldehydes require protection of the amine functional group. On the contrary, aziridines do not condense with aldehydes; the aziridine ring-strain precludes the formation of an iminium ion. Predicated upon this orthogonal reactivity, a stable class of unprotected amino aldehydes has been prepared, and an in-depth investigation into their chemical reactivity has been undertaken. Reactions designed to utilize both their nucleophilic (amine) and electrophilic (aldehyde) centres have demonstrated their capacity to forge multiple bonds in a single transformation, and have been implemented in the synthesis of complex heterocycles and cyclic peptides.

In 1908, H. Emil Fisher attempted to prepare glycinal, an unprotected amino aldehyde, which he found to be inherently unstable and prone to polymerization. This instability arises from the propensity of amines to condense with aldehydes. Accordingly, amino aldehydes require protection of the amine functional group. On the contrary, aziridines do not condense with aldehydes; the aziridine ring-strain precludes the formation of an iminium ion. Predicated upon this orthogonal reactivity, a stable class of unprotected amino aldehydes has been prepared, and an in-depth investigation into their chemical reactivity has been undertaken. Reactions designed to utilize both their nucleophilic (amine) and electrophilic (aldehyde) centres have demonstrated their capacity to forge multiple bonds in a single transformation, and have been implemented in the synthesis of complex heterocycles and cyclic peptides.