No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Over the last forty years the steady use of radical reactions as the key steps in syntheses has increased. The most commonly used radical reagent is tributyl tinhydride. However such tin based radical reagents are toxic and often contaminate the product as they are difficult to remove. As an alternative to these tin reagents, a novel NaBH4/U.V. system was developed. This system was successfully used to effect the radical reduction of various aromatic halides. In light of these results it was thought that other useful transformations such as C-C bond formation could be achieved. Radical cyclisation onto unsaturated bonds, halogen atom transfers radical cyclisation (HATRC) and 1-5 hydrogen atom translocations were explored. This, 1-5 hydrogen atom translocations, methodology has been successfully applied to the synthesis of the spirocyclic natural products (±) horsfiline and coerulescine. With this success the use of the NaBH4/U.V. system on pyridine substrates was explored. Unfortunately this was not achieved with our current understanding of this reaction. However the use of tributylgernamium hydride, which is considered a ‘green’ radical reagent when compared to tin based reagents, proved successful. The novel application of this reagent in the 1-5 hydrogen atom transfer reaction on pyridine substrates was successfully demonstrated. Its use was successfully employed in the synthesis of a pyridine based bioisostere derivative of horsfiline.

Much recent discussion has highlighted the challenges posed by what have variously been called “disruptive”, “discontinuous”, “breakthrough” and “radical” innovations. Although the labelling may vary, the underlying themes appear to be consistent. In particular it is clear that under conditions in which the dominant “rules of the game” change as a result of emergent or shifting markets, major movements at the technological frontier, dislocations in the regulatory environment etc, even organizations with well-developed innovation capabilities get into difficulties. This is less a matter of particular technological, market or political stimuli than of the limitations of the repertoire of organizational responses available to the firm. This resurfaces a long-running concern with managing innovation in two different modes, namely “exploitation” and “exploration”. This thesis reports the results of exploratory research into specific aspects of the organizational culture within the Research and Development (R&D) setting of a small mature UK based company, Cerulean. In doing so it also identifies and discusses key management interventions for developing an innovation culture that facilitates radical product innovation. Cerulean designs and manufactures quality control instrumentation and has in the past been very successful with radically new products. In recent years this propensity for “radicalness” has declined and the company now wishes to regain this capability. A grounded research methodology and a participative action research approach was utilised to surface issues that clearly illustrated both the presence and intensity of aspects of organisation culture that enabled and inhibited radical product innovation. Participative analysis of the data identified nine emerging themes and key constructs of an innovation culture that was found to influence “radicalness” in new product development ventures. The interrelationships between the themes were discussed in the context of current theoretical perspectives in the field of innovation management. This led to the development of a conceptual model that incorporates two “ideal” archetypal forms of innovation culture. A composite instrument was developed based on existing evaluation tools and used to assess the innovation culture. First use of the instrument indicated areas of opportunity in developing a radical innovation culture. Further participative analysis of the emergent themes and the assessment and evaluations of the extant innovation culture, resulted in a series of management interventions to stimulate the development of a culture to facilitate radical product innovation. The design of the interventions was also informed by the literature and other organizations, part of a national Discontinuous Innovation Forum (DIF) undergoing similar ambitions. The proposed interventions comprise a series of linked management actions in the form of a plan to shift the innovation culture of the company closer to a desired radical innovation culture.

Wyosine derivatives are highly complex modified ribonucleic acid (RNA) bases found in archaea and eukarya. They are a modification of a genetically encoded guanosine found at position 37 of phenylalanine encoding transfer ribonucleic acid (tRNA). The second step in the biosynthesis of all wyosine derivatives, in both archaea and eukarya, is the transformation of N-methylguanosine to 4-demethylwyosine by the radical S-adenosyl-l-methionine enzyme TYW1. When these studies were initiated, the substrate of TYW1 was unknown. Four possible substrates; acetyl CoA, acetyl phosphate, phosphoenolpyruvate, and pyruvate; were tested for activity. Only incubation with pyruvate led to production of 4-demethylwyosine. As only two new carbons are incorporated into the RNA base at this step, ¹³C isotopologues were used to identify the carbons that are transferred into 4-demethylwyosine. These experiments revealed that C2 and C3 of pyruvate are incorporated into 4-demethylwyosine, with C1 lost as an unknown byproduct. Utilizing pyruvate containing deuteriums in place of protons on the C3 carbon, the regiochemistry of the addition was determined. It was found that C3 forms the methyl group of 4-demethylwyosine and C2 becomes the bridging carbon in the imidazoline ring. The site of hydrogen atom abstraction by 5'-deoxyadenosyl radical was identified as the N-methylguanosine methyl group through the use of tRNA containing a deuterated methyl group. The putative mechanism for this transformation involved the formation of an enzyme substrate Schiff base through a conserved lysine residue. Utilizing sodium cyanoborohydride a Schiff base was trapped between TYW1 and pyruvate. The mass of the trapped adduct responded as expected when different isotopologues of pyruvate were used, demonstrating that it is due to pyruvate. Moreover, the fragment of TYW1 that contained the trapped adduct contained two lysine residues, one of which was shown to be required for activity both in vivo and in vitro. It was initially proposed that TYW1 contained two iron-sulfur clusters, and then subsequently shown to have two 4Fe-4S clusters. Site directed mutagenesis, along with iron and sulfide analysis identified the cysteines; as C26, C39, and C52; coordinating the second 4Fe-4S cluster. This study identified pyruvate as the substrate of TYW1, and provided evidence for key steps in the transformation of N-methylguanosine to 4-demethylwyosine.