Design of Novel PDHc El Inhibitors as Herbicides

It has been speculated that the salts of 1-(substituted phenoxyacetoxy)aIkylphos-phonic acid could have good herbicidal activity because several salts of acetyl-phosphonic acid (such as sodium methylacylphosphonate 1-1) have been reported as a powerful PDHc El inhibitor. Because of that, five series of novel alkali metal salts of (9-aIkyl 1-(substituted phenoxyacetoxy)alkylphosphonic acids IIA-IIE including 77 compounds were designed and synthesized (Scheme 1.27). 

Based on the bioisosterism, the salts of alkylphosphonates lA or IC were assumed to have a more powerful inhibitory effect against plant PDHc El and better h iddal activity than the corresponding alkylphosphonates, because sodium D-methyl acety-Iphosphonate 1-1 has been reported as a powerful PDHc El inhibitor [1]. Five series of novel alkali metal salts of D-alkyl 1-(substituted phenoxyacetoxy)alkylphosphonates IIA-IIE were first designed as potential plant PDHC El inhibitors. IIA-IIE could be easily synthesized from corresponding D,D-dialkyl 1-(substituted phenoxyacetoxy) alkylphosphonates lA or IC in one step. It was also expected that 1-(substituted phenoxyacetoxy)alkylphosphonic acids (Scheme 3.2) could have better herbicidal activity, because they were more analogous to pymvic acid which acted as the substrate of PDHc. However, 1-(substituted phenoxyacetoxy)alkylphosphonic acids were not stable for long-time storage. 

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