Development of an open-learning module in natural product chemistry

This article describes the author’s personal perspective on the design, production and delivery of an open-learning module in natural product chemistry. This 10 credit, level 6 module is delivered using three tutorial sessions and is assessed by three open-book tests. The study material is available to the students as both hard-copy and electronic copy

New routes to functionalised pyridines

A novel method of preparing substituted pyridines has been developed. This method uses readily available [3-ketoesters and amidrazone as starting materials. The pyridines obtained do not require purification and different substitution patterns, not available by known methods, can be obtained. The formation of 1,2,3-tricarbonyl compounds was achieved by oxidation of the alcohol precursors, following two different methods. a-Chloro-ct-acetoxy-f3-dicarbonyls were prepared in excellent yields and were shown to react as tricarbonyl equivalents in the formation of 1,2,4-triazines. Regioselective condensation reactions were observed between different amidrazones with tricarbonyl and tricarbonyl equivalents to produce a series of novel 1,2,4-triazines in good yields with no contamination by any regioisomer. When 1,2,4-triazines were obtained from a-chloro-a-acetoxy-P-dicarbonyls, 2.5 equivalents of amidrazone were required. However, decomposition of a-chloro-a-acetoxy-P-dicarbonyls prior to reaction with 1 equivalent of amidrazone yielded the 1,2,4-triazines in good yields. These 1,2,4-triazines underwent aza Diels-Alder cycloaddition reactions with 2,5- norbornadiene to give a series of novel 2,3,6-trisubstituted pyridines. The pyridines bearing electron withdrawing groups as substituents could also be obtained in a 'one- pot' reaction from their corresponding tricarbonyls or tricarbonyl derivatives. The 1,2,4- triazines bearing electron donating groups could be converted to their corresponding pyridines either by changing the reaction conditions or, when possible, by conversion of the electron donating group into a more electron withdrawing substituent by oxidation (e.g. sulphoxide substituent). Pyridines bearing a sulphoxide substituent undergo nucleophilic substitutions, giving great scope to introduce different functionality in the C-6 of the pyridines.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Chromogenic enzyme substrates based on [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives for the detection of nitroreductase activity in clinically important microorganisms†

A series of [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives have been synthesised as potential indicators of microbial nitroreductase activity. When assessed against a selection of 20 clinically important pathogenic microorganisms, microbial colonies of various colours (yellow, green, red, brown, black) were produced and attributed to nitroreductase activity. Most substrates elicited colour responses with Gram-negative microorganisms. In contrast, the growth of several species of Gram-positive microorganisms and yeasts was often inhibited by the substrates and hence coloured responses were not seen. Graphical abstract: Chromogenic enzyme substrates based on [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives for the detection of nitroreductase activity in clinically important microorganism