The Total Synthesis of Natural Products via Cascade Reactions

The discipline of natural product synthesis serves to provide a platform for reaction discovery, the development of unique methodology, elucidation of biochemical pathways and structure conformation. This thesis will explore some bio-inspired cascade reactions towards the synthesis of the busseihydroquinone (chapter two), rhodonoid (chapter three), rubiginosin (chapter four) and nyingchinoid (chapter five) families of natural products, through the synthesis and derivatization of chromenes (Scheme 1).1 Efforts towards the total synthesis of the indole alkaloid (±)-hinckdentine A will also be explored (chapter Six).Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 202

Structure, function and mechanism of N-glycan processing enzymes : endo-α-1,2-mannanase and endo-α-1,2-mannosidase

While most glycosidases that act on N-linked glycans remove a single sugar residue at a time, endo-α-1,2-mannosidases and endo-α-1,2-mannanases of glycoside hydrolase family GH99 cut within a chain and remove two or more sugar residues. They are stereochemically retaining enzymes that use an enzymatic mechanism involving an epoxide intermediate. Human endo-α-1,2-mannosidase (MANEA) trims glucosylated mannose residues; the endomannosidase pathway provides a glucosidase-independent pathway for glycoprotein maturation. Cell-active MANEA inhibitors alter N-glycan processing and reduce infectivity of dengue virus, demonstrating that MANEA has potential as a host-directed antiviral target. Sequence-related enzymes from gut Bacteroides spp. exhibit endo-α-1,2-mannosidase activity and are a fruitful test bed for structure-guided inhibitor development. The genes encoding the Bacteroides spp. enzymes sit within polysaccharide utilization loci and are preferential endo-α-1,2-mannanases

R1507, an Anti-Insulin-Like Growth Factor-1 Receptor (IGF-1R) Antibody, and EWS/FLI-1 siRNA in Ewing's Sarcoma: Convergence at the IGF/IGFR/Akt Axis

A subset of patients with Ewing's sarcoma responds to anti-insulin-like growth factor-1 receptor (IGF-1R) antibodies. Mechanisms of sensitivity and resistance are unknown. We investigated whether an anti-IGF-1R antibody acts via a pathway that could also be suppressed by small interfering (si) RNA against the EWS/FLI-1 fusion protein, the hallmark of Ewing's sarcoma. The growth of two Ewing's sarcoma cell lines (TC-32 and TC-71) was inhibited by the fully human anti-IGF-1R antibody, R1507 (clonogenic and MTT assays). TC-32 and TC-71 cells express high levels of IGF-2, while RD-ES and A4573 Ewing's cell lines, which were less responsive to R1507 in our assays, express low or undetectable IGF-2, respectively. TC-71 cells also expressed high levels of IGF-1R, and R1507 decreased steady-state levels of this receptor by internalization/degradation, an effect which was associated with a decrease in p-IGF-1R, p-IRS-1, and p-Akt. EWS/FLI-1 siRNA also decreased p-Akt, due to its ability to increase IGF-BP3 levels and subsequently decrease IGF-1 and IGF-2 levels, thus inhibiting signaling through p-IGF-1R. This inhibition correlated with growth suppression and apoptosis. The attenuation of Akt activation was confirmed in TC-71 and HEK-293 (human embryonic kidney) cells by transfecting them with IGF-1R siRNA. We conclude that antibodies and siRNA to IGF-1R, as well as siRNA to EWS/FLI-1, act via intersecting IGF/IGF-1R signals that suppress a common point in this pathway, namely the phosphorylation of Akt

Pregnancy risks in women with pre-existing coronary artery disease, or following acute coronary syndrome

Objective The objective of this study was to determine outcomes in pregnant women with pre-existing coronary artery disease (CAD) or following an acute coronary syndrome (ACS) including myocardial infarction (MI). Background The physiological changes of pregnancy can contribute to myocardial ischaemia. The pregnancy risk for women with pre-established CAD or a history of ACS/MI is not well studied. Methods This was a retrospective multicentre study. Adverse maternal cardiac, obstetric and fetal/neonatal events were examined. The primary outcome was a composite endpoint of cardiac arrest, ACS/MI, ventricular arrhythmia or congestive heart failure. The prevalence of new or progressive angina during pregnancy was also examined. Results Fifty pregnancies in 43 women (mean age 35 +/- 5 years) were included. Coronary atherosclerosis (40%) and coronary thrombus (36%) were the most common underlying diagnoses. The primary outcome occurred in 10% (5/50) of pregnancies and included one maternal death secondary to cardiac arrest. Other events included ACS/MI (3/50) and heart failure (1/50). New or progressive angina occurred in 18% of pregnancies. Ischaemic complications of any type (new or progressive angina, ACS/MI, ventricular arrhythmia, cardiac arrest) occurred more commonly in women with coronary atherosclerosis compared with those without (50% vs 10%, p=0.003). A high rate of adverse obstetric (16%) and fetal/neonatal (30%) events was observed. Conclusions Pregnant women with pre-existing CAD or ACS/MI before pregnancy are at increased risk of adverse events during pregnancy. Those with coronary atherosclerosis are at highest risk of adverse maternal cardiac events due to myocardial ischaemia during pregnancy