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Unsaturated and fluorinated analogues of aspartyl-beta-phosphate were synthesised as potential inhibitors of the bacterial enzyme aspartate semialdehyde dehydrogenase (ASA-DH). Acetylenic and Z-olefinic analogues showed competitive inhibition, but an E-olefinic analogue was inactive. A monofluoromethylene phosphonate competed poorly, but showed time-dependent inhibition of ASA-DH in the absence of phosphate. Simulated docking procedures were used to rationalise the results. These studies showed that substrate and inhibitor binding are mediated by interaction with two active-site arginine residues, and for likely covalent attachment to the active-site thiol group, electrophilic carbon atoms should be located 4.5 A, or less, from the thiol.

A new, mild and high yielding synthesis of phosphoramidates is described: potassium salts of carboxylic acids are treated with ethylchloroformate and the resulting activated anhydride-carbonates are then treated with LiNH-P(O)(OEt)2 in situ--the methodology is especially suited to acid sensitive systems featuring BOC, tBu or acetal protecting groups.