Date of Award
Master of Science (MS)
Chemistry & Biochemistry
Achieving a high level of efficiency in carbohydrate synthesis is dependent upon reactions that can provide high yields and stereoselectivity at the anomeric position. The nature of the glycosidic bond as either α or β configuration poses the greatest obstacle. The development of methods to control this inherent feature while also giving high yields is a primary goal for the field of carbohydrate chemistry. This thesis examines the potential for two new methods to overcome these challenges: dehydrative glycosylation with cyclic phosphonium anhydrides and glycosylation of glycosyl phosphinites. A collection of cyclic phosphonium anhydrides were prepared and tested with a range of glycosylation substrates. These glycosylations demonstrated good yield and selectivities for a number of examples and represent a new and practical type of dehydrative glycosylation. A number of 1D and 2D NMR experiments were carried out to better understand the mechanistic nature of this reaction. A collection of glycosyl phosphinites were also prepared and evaluated in their potential to give highly α-selective glycosylations through in situ anomerization. This method was used with a number of substrates giving good yield and high selectivities. The high α-selectivity of this method was explored through a number of 31P NMR experiments.
Dockery, Lance Taylor, "New Methods in Carbohydrate Chemistry: Dehydrative Glycosylation with Cyclic Phosphonium Anhydrides and α-Selective Glycosylation of Glycosyl Phosphinites" (2016). Chemistry & Biochemistry Graduate Theses & Dissertations. 201.