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

2,3,4,5-Tetrahydrodipicolinic acid (3) is a key intermediate in the di aminopimelate (DAP) pathway to L-lysine (7). It was synthesized as the stable racemic potassium salt (25) from dipicolinic acid (14) by este rification, hydrogenation to the cis-diester (17), followed by elimina tion of p-toluenesuifinic acid from the N-toluenesulfonyl derivative ( 24) of dimethyl cis-piperidine-2,6-dicarboxylate with concomitant clea vage of the ester groups. (+/-)-2,3,4,5-Tetrahydrodipicolinic acid is unstable in neutral or acidic solution, and in basic solution it exist s in equilibrium with the corresponding enamine (27) and 2-oxo-6-amino adipate (26).