The aim of my PhD is to study rotaxanes. This study is intended to contribute to the understanding of rotaxanes and to provide some insights into the possibilities of their application, and is divided in two parts accordingly. In the first part of my thesis I develop and analyze new hydrogen-bond templates that contain phosphorus and can be used to improve the existing rotaxane formation processes and to synthesize new rotaxanes. The second part of my research is based on the fact that the form of rotaxanes restricts the macrocycle movements to two options only: rotational and translational movement. Thus, in the second part I focus on improving the potential practical application of rotaxanes and on developing and implementing rotational and translational molecular machines, whereby a rotational machine is critical for creating and implementing a translational machine. In the course of this work two different types of a molecular machine (a molecular accelerator and a molecular shuttle) have been created. The results achieved demonstrate that hydrogen bond-based templates containing phosphorus can be used to template the rotaxane formation, and that both movements of macrocycle, translational and rotational, can indeed be used to improve the molecular machines.

The thesis describes synthetic approaches towards chiral aromatic aminodiols, an important structural motif that can also potentially be prepared via the sequential use of transketolase (TK) and transaminase (TA). Syntheses of aminopyruvates and analogues as novel TK donors are also described. Initially, the aims of this Ph. D. are laid out in Chapter 1 a literature review of the uses of enzymes in chemoenzymatic syntheses is covered. In particular, carbon-carbon bond forming enzymes (TK) from a family of thiamine pyrophosphate enzymes are discussed. The latter part of Chapter 1 explores the use of TAs to convert ketone groups to amino groups stereoselectively. Chapter 2 is concerned with current synthetic strategies towards the synthesis of aminodiols and the Sharpless asymmetric aminohydroxylation (AA). This is a key reaction in establishing chiral aminoalcohol functionalities. The results and discussion are described in Chapter 3 to Chapter 5. Chapter 3 outlines a systematic approach towards nitrogen containing pyruvate donors, via a number of synthetic protocols, for potential use with TK and TK mutants. Finally, a TK mimetic reaction is presented with the successful synthesis of 3-phthalimidopyruvate. Synthetic approaches towards aromatic aminodiols via a short reaction sequence for use as HPLC standards are outlined in Chapter 4. Initially, one-pot methodologies were explored to access both syn and arcf/'-diastereomers and are described. Using 'masked' aromatic syn-aminodiols, the methodology for producing aromatic sy/7-aminodiols via a short reaction sequence is described along with the synthesis of cinnamate precursors for the Sharpless asymmetric aminohydroxylation (AA) reaction. Finally, the results of Sharpless AA reactions via homogeneous and heterogeneous catalytic conditions with cinnamate precursors are presented in Chapter 5. An overall summary and future areas of research in the future are discussed in Chapter 6, whilst a formal description of the experimental methods and procedures employed in this thesis are presented in Chapter 7.

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Some historical aspects of the oxidation reactions of 1,1-disubstituted hydrazines are reviewed. In particular, the evidence for the proposed intermediacy of diazenes in these reactions is outlined and the nature of the oxidation products is considered in the broader context of diazene-generating reactions. The synthesis of l-alkyl-l-phenylhydrazines has been examined and several preparative procedures are discussed. The alkylation of the sodium salt of phenylhydrazine with the appropriate alkyl halides was found to be the most successful method; the hydrazines prepared in this way all had substituents of the allylic type. Purification (to remove residual phenylhydrazine) can be achieved by selective recrystallisation of the hydrochloride derivative from benzene. Some limitations of this general method are described. The oxidation studies were carried out using lead tetra-acetate and mercuric oxide. The oxidative rearrangement of 1-allyl-l-phenyltiydrazine to 1-phenylazoprop-2-ene was confirmed, and by regarding this as the model system, formation of particular species from the other hydrazines was envisaged. The outcome of each oxidation study is discussed in detail. The oxidation of 1-(pent-3-en-2-yl)-1-phenylhydrazine was studied in the contextof a proposed method of examining the base-catalysed rearrangement of an optically active azo-compound (formed in the oxidative rearrangement of the optically active hydrazine). Preliminary studies on the racemic hydrazine indicate that the azo compound is obtained in the form of two geometrical isomers. The synthesis of l-phenylazoprop-2-ene by an unambiguous route is described; the method should have wider potential. A proposed method of determining the electronic character of the diazene involved in the oxidative rearrangement of allylic hydrazines, and difficulties encountered in its application are described. The attempted interception of the intermediate diazenes by dimethyl sulphoxide and dimethyl sulphide is described. Oxidation of the hydrazines with cupric chloride was found to give copper-containing solids whose exact composition could not be determined.

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This thesis is concerned with the synthesis of the class of interlocked molecular architectures called rotaxanes. Currently rotaxanes can be synthesized in high yields by exploiting noncovalent interactions between reacting fragments. The success of these supramolecular approaches are detailed in Chapter 1 and are contrasted with early attempts at their synthesis, which were low yielding. The novel properties of interlocked molecular architectures are also elaborated, emphasizing their potential as molecular level machines. Chapter 2 contains a detailed study of the hydrogen bond-directed synthesis of benzylic amid macrocycle-containing [2]rotaxanes. This task is performed by structural variation of the linear thread component in the standard five-component clipping reaction. The introduction of flexibility, non-optimal binding motifs, and the removal of key noncovalent interactions provide an insight into this remarkable process. In addition to analysis of the resulting yields of the [2]rotaxanes, the interlocked products are characterized by <i>X</i>-ray crystallography and ¹H NMR spectroscopy affording further insights into the specific structural requirements needed for subsequent interlocking. After a detailed study of this hydrogen bond-directed interlocking process, in Chapter 3 we synthesize a rotaxane, in high yield, whose components bear no formal recognition elements. In Chapter 4 we extend the concept of a MIA by demonstrating the function of a second-generation MIA based on a fumaramide template. The advantages of the fumaramide-based MIA are seen in the increased yield obtained for the benzylic amide-containing macrocycle rotaxane, but are slightly offset by the inclusion of a necessary photoisomerization step.

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