Conceptions and expectations of mentoring relationships in a teacher education reform context

Peer reviewedPostprin

Macromolecular 4-aminoquinoline compounds as potential antimalarial drugs

4-Aminoquinolines have a long and successful history as antimalarials as they have provided a number of useful antimalarials. P. falciparum, a causative organism of the most deadly form of human malaria, is generally slow to develop resistance to these drugs. 4-Aminoquinoline derivatives appear to bind to nucleoproteins and interfere with protein synthesis in susceptible organisms; the drugs intercalate readily into double-stranded DNA and inhibit both DNA and RNA polymerase. In addition, 4-aminoquinolines are found to concentrate in parasites’ digestive vacuoles, thereby increasing the pH of the vacuoles, and thus interfere with the parasites’ ability to metabolize. 4-Aminoquinolines on the other hand have raised considerable interest because of their anti-carcinogenic properties and their ability to inhibit tumor development and presently are being used in combination therapy with anti-cancer drugs to inhibit development of drug resistance in cancer cells caused by anti-cancer drugs. 8-Aminoquinoline mechanism is quite different from that of 4-aminoquinoline in that the 8-aminoquinolines are converted in the liver to an active quinone metabolite creating oxygen free radicals that interfere with the plasmodial electron chain transport chain during respiration. Anti-cancer drugs are often toxic when delivered straight, but the bioreversible drug conjugation of anticancer drugs to water-soluble macromolecular carriers has proved to enhance the therapeutic effectiveness of anticancer drugs. Following facilitated pharmacokinetics pathways, the conjugates, acting as prodrugs, will release the active drug species in the transformed target cells and their designs are geared towards reducing pharmacological barriers of toxicity, drug resistance and poor bioavailability encountered with currently used anti-cancer drugs. In order to demonstrate the multidrug binding capacity of polyaspartamide, the co-conjugation of 4- and 8-aminoquinoline derivatives with anti-cancer agents was achieved, and the co-conjugates are expected to serve as resistance-reducing agents. This present project aimed at the anchoring of 4-aminoquinoline to various amine functionalized polymeric carriers, and selected macromolecular 4-aminoquinoline compounds were screened for in vitro antiplasmodial activity

Safeguards: A key process safety tool in jet fuel management from refinery to aircraft wings

Emphasis on aviation safety and the drive for an industry safety revolution sadly came as an aftermath of several aircraft accidents and fatalities. In Nigeria alone, 112 aircraft crashes were recorded from 1939 to 2015. Safety concerns in the Nigerian aviation sector reached a peak in 1996 when within 2 years; seven air crashes with hundreds in fatalities, were recorded. This led to several industry reviews, regulations and operational status appraisal resulting in the closure and abandonment of the only 94 km hydrant jet fuel pipeline from Atlas Cove via Mosimi to Lagos Airport, by the Government in 1996 to this day. This paper critically examines the improvements in practice, and the jet fuel safety and quality management systems currently in place as at 2017, for the handling of jet fuel toward ensuring on-spec jet A-1 fuel with a focus on Lagos aviation fuel operations. The findings show that different forms of safeguards have been deployed along the jet fuel value chain to maintain product quality and ensure flight safety, but there are rising concerns that the industry may relapse on safety due to the current economic recession

Isomerisation and ring closing metathesis reactions towards benzo-fused heterocyclic compounds

Student Number : 0410864E - MSc dissertation - School of Chemistry - Faculty of ScienceThe aim of the project described in this dissertation is to explore the application of ring closing metathesis (RCM) to the synthesis of 6-, 7-, 8- and 9-membered N,N-, N,O- and O,O-benzo-fused heterocyclic compounds which are interesting structural motifs in medicinal chemistry. In recent times, their structures have been widely used as molecular scaffolds. Some of these heterocycles have been identified as antitumour agents, antibiotics and anti-HIV agents. In our laboratories, a variety of 6-, 7- and 8-membered nitrogen- and oxygen- containing benzo-fused rings have been synthesized through ruthenium-mediated isomerisation and RCM in moderate to good yields. The first step in the present project was N-protection of suitable 2-aminophenols or o-phenylenediamines followed by allylation. Rutheniummediated isomerisation followed by RCM was then used for the synthesis of the 6- membered ring system tert-butyl 4H-1,4-benzoxazine-4-carboxylate 91 and the 7- membered ring system tert-butyl 1,5-benzoxazepine-5(4H)-carboxylate 103 while only RCM was used for the 8-membered ring systems, di(tert-butyl) 2,3,4,5-tetrahydro-1,6- benzodiazocine-1,6-carboxylate 130, di(tert-butyl) 2,5-dihydro-1,6-benzodiazocine-1,6- dicarboxylate 129, 1,6-dibenzoyl-1,2,5,6-tetrahydro-1,6-benzodiazocine 132, 7-methoxy- 2,5-dihydro-1,6-benzodioxocine 137 and the 9-membered ring system 1,6-bis[(4- methylphenyl)sulfonyl]-2,5,6,7-tetrahydro-1H-1,6-benzodiazonine 159. In the synthesis of the 7-membered ring systems, based on established methodology, we encountered problems with the RCM from suitable benzylamine or benzyl alcohol precursors. The reasons for this are not clear but we suspect this could be as a result of electronic and kinetic factors. Nevertheless, we were able to synthesize a 7-membered ring system, tert-butyl 1,5-benzoxazepine-5(4H)-carboxylate 103, from a readily available precursor using a different methodology. Approaches to the synthesis of the 8-membered ring systems, di(tert-butyl) 2,3,4,5- tetrahydro-1,6-benzodiazocine-1,6-carboxylate 130, di(tert-butyl) 2,5-dihydro-1,6- benzodiazocine-1,6-dicarboxylate 129, 1,6-dibenzoyl-1,2,5,6-tetrahydro-1,6- benzodiazocine 132 and 7-methoxy-2,5-dihydro-1,6-benzodioxocine 137, as described in this dissertation, made extensive use of RCM in moderate to good yields, but the deprotection of the Boc group after hydrogenation proved to be a problem. The synthesis of the 9-membered nitrogen containing benzo-fused compounds, 1,6- bis[(4-methylphenyl)sulfonyl]-2,5,6,7-tetrahydro-1H-1,6-benzodiazonine 159 by RCM was successful but in the synthesis of the N,O-benzo-fused compound by RCM, we suspect that polymerization, which is a side reaction in RCM reactions that are slow, occurred. In the synthesis of the 9-membered O,O-benzo-fused compounds, we only isolated the starting material. The final approach in this dissertation involved the use of ruthenium-mediated isomerisation to afford internal isomerisation of the double bond within the heterocyclic rings of the 8-membered and 9-membered benzo-fused compounds previously prepared in our laboratory. This gave a mixture of regioisomers of 10-methoxy-2,3-dihydro-1,6- benzodioxocine 163 and 7-methoxy-2,3-dihydro-1,6-benzodiazocine 164, 1,6-bis[(4- Methylphenyl)sulfonyl]-1,2,3,6-tetrahydro-1,6-benzodiazocine 166, a regioisomeric mixture of 6-[(4-methylphenyl)sulfonyl]-3,6-dihydro-2H-1,6,-benzoxazocine 161 and 6-[(4-methylphenyl)sulfonyl]-5,6-dihydro-4H-1,6,-benzoxazocine 162, and the 9- membered benzo-fused ring system, 1,6-bis[(4-methylphenyl)sulfonyl]-2,3,6,7- tetrahydro-1H-1,6-benzodiazonine 170. The yields were good and the solid state structures of these isomerised compounds were examined by X-ray crystallography. Xray diffraction was also performed on the solid state 8- and 9-membered benzo-fused ring systems. We also compared the crystal structures of the 8- and 9-membered benzo-fused compounds with their isomerised compounds

Smoothing food price trends in Nigeria: Political economy issues and policy vistas

This study reviews the political economy issues surrounding the 2008 food crisis in Nigeria; the lessons learned from management of the crisis; analyses the performance of policies aimed at stabilizing prices; and proffers policy measures for preventing future occurrence. The study finds that the country has not been under any threat of food crisis since the 2008 episode. Since 2011, medium-term policies and strategies are redesigned and entrenched as major components of the agricultural transformation agenda. The implementation of the agenda has led to an increase in domestic food production, reduction in food imports, and stabilization of food prices