Synthesis of Enzyme Inhibitors of L-Lysine Biosynthesis

[摘要] There are two possible biosynthetic pathways to the essential amino acid L-lysine. The diaminopimelate pathway occurs in higher plants and bacteria and the a-aminoadipate pathway operates in fungi and yeast. This thesis is concerned with the first two steps in the diaminopimelate pathway to L-lysine, catalysed by dihydrodipicolinate synthase (DHDPS) and dihydrodipicolinate reductase (DHDPR). Synthesis of substrates involved in the DHDPS and DHDPR steps, namely aspartate semialdehyde (A), 2,3-dihydro-dipicolinic acid (B) and 2,3,4,5-tetrahydrodipicolinic acid (C) was attempted. DL-Aspartate semialdehyde was prepared by the ozonolysis of DL-allylglycine for use in the enzyme assay of DHDPS. Attempts were made to synthesise 2,3-dihydro-dipicolinic acid (B) from aspartate semialdehyde and oxaloacetic acid. However the final product was dipicolinic acid, probably formed by oxidation of the unstable 2,3-dihydrodipicolinic acid (B). The synthesis of 2,3,4,5-tetrahydrodipicolinic acid (C) was achieved. This involved the preparation of dimethyl N-tosyl-cis-2,6-piperidinedicarboxylate (E). Treatment of the N-tosyl derivative with potassium t-butoxide resulted in the elimination of toluenesulphinic acid, forming the required imine (C). The imine (C) was found to exist in solution in equilibrium with the enamine and the open chain compound. Imines derived from L-proline and DL-pipecolinic acid were also prepared using the same route. Inhibition of the biosynthesis of the essential amino acid, L-lysine, is of great interest as inhibitors of the pathway may have herbicidal or antibacterial activity without mammalian toxicity. A number of compounds were synthesised and tested as inhibitors of dihydrodipicolinic acid synthase. Analogues of dipicolinic acid (D) were made. Dipicolinic acid was converted into 2,6-pyridinedicarboxamide. Dehydration of 2,6-pyridine-dicarboxamide gave 2,6-pyridinedinitrile. Using the dinitrile the diimidate and the ditetrazole (F) were prepared for testing as inhibitors of DHDPS. Using chelidonic acid (G) and chelidamic acid (H), N-alkyl chelidamic acids were prepared and tested as enzyme inhibitors of DHDPS. Esteriflcation of these compounds was carried out using methanol and conc. sulphuric acid to provide more compounds for testing in the enzyme assay. A number of analogues of 2,6-piperidinedicarboxylic acid were prepared. N-Methyl-2,6-piperidinedicarboxylic acid and its N-oxide (I) were synthesised from cis-2,6-piperidine-dicarboxylic acid. l,4-Pentadien-3-one-1,5-dicarboxylic acid was prepared from 2-furanacrylic acid. Cyclisation of 2-furan-acrylic acid afforded piperidin-4-one-2,6-dicarboxylic acid (J). Cyclisation with methylamine yielded the N-methyl derivative. All our synthesised compounds were tested as inhibitors of dihydrodipicolinic acid synthase enzyme.

[发布机构] University:University of Glasgow

[关键词] Organic chemistry