Ewan J. T. Chrystal

Complexation of diquat and paraquat by macrocyclic polyethers incorporating two dibydroxynaphthalene residues

Abstract NMR Spectroscopy and FAB mass spectrometry demonstrate that the 38-crown-10 (1/5DN38C10) and 35-crown-9 (1/5DN35C9) ethers incorporating two 1,5-di-naphtho units form 1:1 complexes with the Paraquat [PQT] 2+ and Diquat [DQT] 2+ dications in solution. In the solid state, the [PQT.1/5DN38C10] 2+ complex is stabilised by face-to-face (π/π charge transfer) interactions between the naphtho and bipyridinium rings, whereas the free 1/5DN35C9 receptor features a classic edge-to-face (H δ+ /π electrostatic) interaction between its two naphtho rings.

SYNTHESIS OF A KEY INTERMEDIATE IN THE DIAMINOPIMELATE PATHWAY TO L-LYSINE: 2,3,4,5-TETRAHYDRODIPICOLINIC ACID

Abstract 2,3,4,5-Tetrahydrodipicolinic acid ( 3 ) is a key intermediate in the diaminopimelate (DAP) pathway to l -lysine ( 7 ). It was synthesized as the stable racemic potassium salt ( 25 ) from dipicolinic acid ( 14 ) by esterification, hydrogenation to the cis -diester ( 17 ), followed by elimination of p -toluenesulfinic acid from the N -toluenesulfonyl derivative ( 24 ) of dimethyl cis -piperidine-2,6-dicarboxylate with concomitant cleavage of the ester groups. (±)-2,3,4,5-Tetrahydrodipicolinic acid is unstable in neutral or acidic solution, and in basic solution it exists in equilibrium with the corresponding enamine ( 27 ) and 2-oxo-6-aminoadipate ( 26 ).

Pyridine and piperidine derivatives as inhibitors of dihydrodipicolinic acid synthase, a key enzyme in the diaminopimelate pathway to l-lysine

Abstract A key step in the diaminopimelate (DAP) pathway to l -lysine ( 7 ) involves condensation of pyruvate with aspartic acid β-semialdehyde ( 1 ) to yield l -2,3-dihydrodipicolinic acid ( 2 ) (DHDPA) catalyzed by DHDPA synthase. The best inhibitors of DHDPA synthase of the thirty pyridine and piperidine derivatives prepared were the N -oxide ( 15 ) of dipicolinic acid and the di-imidate ( 13 ) of dimethyl pyridine-2,6-dicarboxylate each with an IC 50 value of 0.2 mM. The N -oxide ( 15 ) and dinitrile ( 12 ) are non-competitive inhibitors with K i values of 0.29 and 1.25 mM against aspartate semialdehyde and 0.06 and 0.34 mM against pyruvate, respectively.

The self-assembly of a highly ordered [2]catenane

Template-directed synthesis has been used to construct a [2]catenane in which the two molecular components, the cyclobis(paraquat-p-phenylene) tetracation and 1,5-dinaphtho-38-crown-10, are found to be ordered non-covalently with respect to each other in both the solid (by X-ray crystallography) and solution (by NMR spectroscopy) states and to influence each other to the extent of establishing electrochemical gradients for the stepwise one electron reductions of the two paraquat units.

Synthesis of the potassium salt of 2,3,4,5-tetrahydrodipicolinic acid, a key intermediate in the diaminopimelate pathway to L-lysine

Abstract The potassium salt (13) of 2,3,4,5-tetrahydrodipicolinic acid, a key intermediate in the diaminopimelate (DAP) pathway to L-lysine (7), has been prepared by elimination of p -toluenesulphinic acid from the N -toluenesulphonyl derivative ( 12 ) of dimethyl cis -piperidine-2,6-dicarboxylate with simultaneous cleavage of the ester groups. 2,3,4,5-Tetrahydrodipicolinic acid exists in solution in equilibrium with the corresponding enamine ( 15 ) and an open chain form ( 14 ), and serves as a substrate for meso -DAP dehydrogenase on the biosynthetic pathway to L-lysine ( 7 ).