Difluoromethylene analogues of aspartyl phosphate: the first synthetic inhibitors of aspartate semi-aldehyde dehydrogenase

Abstract

The difluoromethylene analogue of aspartyl phosphate 6 has been prepared by the fluoride catalysed coupling of diethyl trimethylsilyldifluoromethyl phosphonate with an appropriate aldehyde followed by Dess-Martin oxidation and deprotection; the deprotected compound inhibited (KI 95 microM) aspartate semi-aldehyde dehydrogenase, a key enzyme involved in bacterial amino acid and peptidoglycan biosynthesis.

A New Branch in the Family: Structure of Aspartate-β-semialdehyde Dehydrogenase from Methanococcus jannaschii

“…14 The most potent synthetic inhibitor of ASADH identified to date is the difluorophosphonate analog of aspartyl phosphate with a K i of 95 mM. 15,16 In addition to its role in aspartate metabolism, ASADH from the archaea Sulfolobus solfataricus has been shown recently to exhibit RNase activity. 17 The RNase activity has been localized within the N-terminal 73 amino acid residues, which is part of the nucleotide-binding domain of ASADH.…”

Capture of an intermediate in the catalytic cycle of l -aspartate-β-semialdehyde dehydrogenase

“…Perturbations to the asd gene have been shown to be lethal to the microorganism, and bacterial strains with this gene deletion are auxotrophic for DAP (4). Because of the importance of this enzyme in amino acid biosynthesis, there is an ongoing interest in the development of effective microbial ASADH inhibitors (5)(6)(7).…”

Aspartyl Phosphonates and Phosphoramidates: The First Synthetic Inhibitors of Bacterial Aspartate-Semialdehyde Dehydrogenase

“…ASA (8) itself was synthesised from allylglycine in a simple procedure involving ozonolysis in 1 M aqueous HCl followed by treatment with dimethyl sulfide. [22] The resulting aqueous solution containing ASA (8) and dimethyl sulfoxide (DMSO) was stable when stored at À 20 8C for prolonged periods, showing no diminished activity in ASA-DH assays over time.…”

“…The enzyme utilises phosphate as an excellent nucleofuge and we reasoned that attenuation of the leaving group ability could provide inhibitory compounds. Thus, difluorophosphonate 12 [8] and phosphonate 13 were considered as potential substrate mimics. In the case of the difluorophosphonate 12 it could reasonably be expected that enhanced electrophilicity of the g-carbonyl group could lead to significant covalent attachment to the active site nucleophile.…”

“…(F,P) 84.1 Hz, keto), À 122.6 (dd, 1 F, 2 J(F,F) 301 8. Hz, 2 J(F,P) 90.6 Hz, hydrate), À 123.5 (dd, 1 F, 2 J(F,F) 300.0 Hz, 2 J(F,P) 0 3.…”