
Kinetic Analyses. DXP synthase activity was measured spectrophotometrically using IspC as a coupling enzyme as previously reported [2] [3] The concentration of D-GAP in stock solutions was determined as previously reported [1] .
All experiments were performed in duplicate. Pyruvate dehydrogeanse activity was measured spectrophotometrically as previously reported [4] by measuring changes in optical density at 340 nm. The basic assay medium (30°C), contained 100 mM HEPES (pH = 8.0), 1 mg/mL BSA, 0.2 mM ThDP, 0.1 mM coenzyme A, 1 mM MgCl 2 , 2 mM cysteine, 0.3 mM TCEP. The reaction was initiated with enzyme. Transketolase activity was measured as previously reported by measuring changes in optical density at 340 nm [5] . The basic assay medium (37°) contained 50 mM glycylgylcine (pH = 7.7), 10 mM sodium arsenate, GADPH, 3.2 TCEP, 2.5 CaCl 2 , 80 µM ThDP, 70 µM xylulose-5-phosphate, 0.5 mM ribose-5-phosphate, 0.4 mM β-nicotinamide adenine dinucleotide phosphate sodium salt hydrate (NAD+). The reaction was initiated with enzyme.
Inhibition Studies. Suppression of DXP synthase activity was measured spectrophotometrically using IspC as a coupling enzyme and monitoring NADPH consumption by IspC [3] [2] . DXP synthase reaction mixtures containing 100 mM HEPES buffer, pH 8.0 (described above) were pre-incubated at 37°C for 5 minutes with compound 1 (2.5, 5, and 10 μM), compound 2 (10, 25, and 50 μM), compound 3 (10, 25, and 50 μM), and compound 4 (250, 500, and 750 μM). The reaction was initiated with enzyme. Inhibition of DXP synthase by compounds 5-6 was not observed. Suppression of pyruvate dehydrogenase activity was measured spectrophotometrically by measuring changes in optical density at 340 nm. Pyruvate dehydrogenase reaction mixtures containing 100 mM HEPES buffer, pH 8.0 (described above) were pre-incubated at 30°C for 5 minutes with compound 1 (50, 100, 250 μM), compound 2 (50, 100, 250 μM), compound 3 (200, 500, 1000 μM). Inhibition of porcine pyruvate dehydrogenase by compounds 4-6 was not observed up to 1 mM. Inhibition of the coupling enzyme (IspC) and transketolase from baker's yeast by compounds 1-6 was not observed up to 1 mM. All experiments were performed in duplicate. Double reciprocal analysis of data was carried out using GraFit version 7 from Erithacus Software. 
Synthesis
General Experimental. Trialkyl phosphites, acyl chlorides and lithium bromide were obtained from commercial sources and used without further purification. Anhydrous acetonitrile was purchased in Sure-Seal bottles. All reactions were carried out in oven-dried glassware under an inert argon atmosphere. NMR spectra were recorded on a Bruker 400 MHz spectrometer for dialkyl acyl phosphonate intermediates, or a Varian 500 MHz spectrometer for final compounds. Chemical shifts are reported in units of parts per million (ppm), relative to a standard reference point.
reference (1) (MAP) was reported previously [2] . Compound (5) (MBP) was prepared according to published protocol [6] .
Synthesis of ethyl acetyl phosphonate (2).
An oven-dried flask was equipped with a stir-bar and charged with 0.21 mL of acetyl chloride (0.24g, 3.0 mmol). Triethyl phosphite (0.52 mL, 3.0 mmol) was added drop-wise at room temperature. The solution was stirred at room temperature for about 1 hour, until triethyl phosphite had disappeared (as indicated by 31 P NMR analysis). Diethyl acylphosphonate (7) was isolated as a pale yellow oil following vacuum distillation (241.6mg, 97% pure as determined by 31 P NMR, 45% yield) and was carried on without further purification. Diethyl acylphosphonate (7) was dissolved in 1.7 mL of anhydrous acetonitrile. Lithium bromide (106.8 mg, 1.2 mmol) was added in one portion, and the reaction mixture was heated to 70 o C and stirred overnight. The resulting white solid was filtered and washed with two 10 mL portions of anhydrous acetonitrile followed by two 10 mL portions of diethyl ether. Ethyl acetylphosphonate (2) was isolated as a white solid (132.5 mg, 69% yield). 
Synthesis of butyl acetyl phosphonate (3).
An oven-dried flask was equipped with a stir-bar and charged with 0.40 mL of acetyl chloride (0.44g, 5.6 mmol). Tributyl phosphite (1.5 mL, 6.0 mmol) was added drop-wise at room temperature. The solution was stirred at room temperature for about 1 hour, until tributyl phosphite had disappeared (as indicated by 31 P NMR analysis). Dibutyl acylphosphonate (8) was isolated as a pale yellow oil following vacuum distillation (754mg, 90% pure as determined by 31 P NMR, 64% yield) and was carried on without further purification. Dibutyl acylphosphonate (8) was dissolved in 4 mL of anhydrous acetonitrile. Lithium bromide (269.7 mg, 3.1 mmol) was added in one portion, and the reaction mixture was heated to 70 o C and stirred overnight. The resulting white solid was filtered and washed with two 10 mL portions of anhydrous acetonitrile followed by two 10 mL portions of diethyl ether. Butyl acetylphosphonate (3) was isolated as a white solid (261.1 mg, 44%). 
Synthesis of methylpropionylphosphonate (4).
An oven-dried flask was equipped with a stir-bar and charged with 0.50 mL of propionyl chloride (0.53g, 5.5 mmol). Trimethyl phosphite (0.60 mL, 5.1 mmol) was added drop-wise at room temperature. The solution was stirred at room temperature for about 1 hour, until trimethyl phosphite had disappeared (as indicated by 31 P NMR analysis). Dimethyl propionylphosphonate was isolated as a pale yellow oil following vacuum distillation (542.3 mg, 98% pure as determined by 31 P NMR, 64% yield) and was carried on without further purification. Dimethyl propionylphosphonate was dissolved in 4 mL of anhydrous acetonitrile. Lithium bromide (269.7 mg, 3.1 mmol) was added in one portion, and the reaction mixture was heated to 70 o C and stirred overnight. The resulting white solid was filtered and washed with two 10 mL portions of anhydrous acetonitrile followed by two 10 mL portions of diethyl ether. Methyl propionylphosphonate (3) was isolated as a white solid (241.0 mg, 47%). 
Synthesis of methylvaleroylphosphonate (6).
An oven-dried flask was equipped with a stir-bar and charged with 0.3 mL of valeroyl chloride (0.3g, 2 mmol), to which 0.3mL of trimethyl phosphite (0.3g, 2 mmol) was added. After one hour, reaction mixture was diluted with 3.1 mL of anhydrous acetonitrile. To this solution, 220 mg of LiBr (2.53 mmol) was added in one portion. The reaction mixture was warmed to 70 o C overnight. The solid white precipitate was filtered with two 10 mL portions of anhydrous acetonitrile, followed by two 10 mL portions of diethyl ether. Methyl valeroylphosphonate was isolated as a white solid (110.3mg, 23% overall yield). 

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