This work describes the application of spiroligomers as serine hydrolases mimetics. Through collaboration with Kendall Houk's group, for the first time in the Schafmeister lab, we demonstrate that "theozymes" can be successfully used as models to design highly functionalized spiroligomer constructs for organocatalysis. We demonstrate a structure-function relationship between the structure of a series of bi-functional and tri-functional spiroligomer based transesterification catalysts and their catalytic activity. First, we designed and synthesized a series of stereochemically and regiochemically diverse bi-functional spiroligozymes to identify the best arrangement of a pyridine as a general base catalyst and an alcohol nucleophile to accelerate attack on vinyl trifluoroacetate as an electrophile. The best bifunctional spiroligozyme reacts with vinyl trifluoroacetate to form an acyl-spiroligozyme conjugate 2.7x103-fold faster than the background reaction with benzyl alcohol. We then incorporated an additional urea functional group to activate the acyl-spiroligozyme intermediate through hydrogen bonds and enable acyl transfer to methanol. The best trifunctional spiroligozyme carries out multiple turnovers and acts as a transesterification catalyst with k1/kuncat of 2.2x103 and k2/kuncat of 1.3x102. Quantum mechanical calculations identified four transition states in the catalytic cycle and provided a detailed view of every stage of the transesterification reaction. With the aim of accelerating the k2, we sought to design better oxyanion holes that hold multiple hydrogen bonding groups in close proximity of the catalytic groups. A macrocyclic motif would be a good candidate to force the oxyanion hole arm to arrange hydrogen-bonding groups in a precise three-dimensional constellation for transition state stabilization. In Chapter 4, we introduce an in silico designed macrocyclic spiroligomer, which overlays well with catalytic active site of an inhibitor bound-esterase. Finally, we detail our effort to develop new methodologies for rapidly synthesizing spiroligomers on solid-support. This would allow us to efficiently permute their structures for diverse applications such as organocatalysts, host molecules, and biologically related applications such as inhibiting protein-protein interactions. / Chemistry

This study focuses on the development of novel two-stage esterification-transesterification synthesis of biodiesel from used cooking oil (UCO) using novel heterogeneous catalysts. The esterification of the UCO was investigated using three types of ion exchange resins catalysts including Purolite D5081, Purolite D5082 and Amberlyst 15. Of all the catalysts investigated, Purolite D5081 resin showed the best catalytic performance and was selected for further optimisation studies. From the optimisation study, it was found that the external and internal mass transfer resistance has negligible effect on the esterification reaction. At the optimum reaction conditions, Purolite D5081 achieved 92% conversion of FFA. During reusability study, the conversion of FFA dropped by 10% after each cycle and it was found that progressive pore blockage and sulphur leaching were dominant factors that decreased the catalytic performance of the Purolite D5081 catalyst. A kinetic modelling for FFA esterification was carried out using Purolite D5081 as a catalyst. Three types of kinetic models were investigated i.e. pseudo homogeneous (PH), Eley-Rideal (ER) and Langmuir-Hinshelwood-Hougen-Watson (LHHW). Experimental data obtained from the batch kinetic studies was successfully represented by the PH model and a good agreement between experimental and calculated values was obtained. The activation energy for esterification and hydrolysis reaction was found to be 53 and 107 kJ/moL. The transesterification of pre-treated cooking oil (P-UCO) was investigated using various types of heterogeneous catalysts including Purolite CT-122, Purolite CT-169, Purolite CT-175, Purolite CT-275, Purolite D5081, Diaion PA306s and Cs-supported heteropolyacids catalysts. Of all the catalysts investigated, Diaion PA306s catalyst showed the highest conversion of triglycerides and was selected for further optimisation studies. At the optimum reaction conditions, Diaion PA306s achieved ca. 75% of triglycerides conversion. During the reusability study, Diaion PA306s catalyst gave a similar conversion of triglycerides after being reused once. Therefore, it was concluded that the resin can be used several times without losing catalytic activity. Several purification methods have been investigated and dry washing method was chosen as the best alternative for biodiesel purification.