A CHEMICAL-MODEL FOR THE FRAGMENTATION REACTION IN THYMIDYLATE SYNTHASE CATALYSIS - SYNTHESIS AND EVALUATION OF A 5-METHYLENE-1-(1,2,3,4-TETRAHYDROQUINOLYL)-6-ALLYLURIDINE

Compounds 5 and 6 were synthesized as models to investigate the reactivity of proposed intermediate 2 in thymidylate synthase (TS) catalysis as it fragments to form dTMP. The mechanism of the fragmentation (homolytic or heterolytic) of model 6 was determined via subsequent interaction of the fragmented center with the C6 allyl substituent. The results were consistent with an ionic fragmentation of 6, followed by loss of an allylic proton, and subsequent thermal electrocyclic or Diels-Alder reactions of the resulting trienes 13 and 14, respectively. Independent generation of radicals analogous to that produced from a radical fragmentation of model 6 did not result in formation of trienes 13 and 14.