2404 J. zyxwvutsrq Org. Chem. 1989,54, zyxwvu 2404-2409 30.25, zyxwvutsrqpo 30.34,30.46,30.50,35.02,38.93,38.93,43.29,44.46,87.05, 115.62, 138.79, 159.61, 163.56, 223.2, 223.2. Concentrated HN03 Oxidation. A 25-mg sample of 1 was dissolved in about 2 mL of ice-cold concentrated nitric acid. The solution was stirred for 2 h at room temperature and then heated at 100 "C for 24 h. Contents of the cooled solution were diluted with water (25 mL) and freeze-dried to yield 15 mg of crystalline solid. Thermospray masa spectrum revealed the presence of three dicarboxylicacids, namely, pimelic, suberic, and azelaic acids zyxwvuts [ (M + 1) 161, 175, and 189 and intensity 60%, loo%, and 38%, respectively]. This was confirmed by TLC [Analtech, silica gel plates, solvent system zyxwvutsr 1-butanol-xylenephenol-formic acid-water, 10703082 (v/v), showed Rfvalues 0.3,0.4, and 0.45, respectivel~]~ and paper chromatographic comparisons (Whatman No. 1 paper, solvent system 1-propanol-2 N ammonia, 7030, R, 0.32,0.38, and 0.44, respectively),' with authentic samples. Hydrolysis with Barium Hydroxide. A solution of 50 mg (0.1 mM) of 1 in 15 mL of 0.5 N barium hydroxide was refluxed for 20 h. The aqueous hydrolysate was filtered and acidified to pH 5.0 with sulfuric acid, the precipitated barium sulfate was removed, and the fiitrate was lyophilized to give 36.7 mg of crude solid [FABMS 415 (M + H)]. (6) Rajagopal, N. S.; Saraswathy, P. K.; Subbaram, M. R.; Achaya, K. (7) Howe, J. R. J. Chromatogr. 1960, 3, 389. T. J. Chromatogr. 1966,24,217. This crude solid was acetylated by stirring with 10 mL of a mixture of acetic anhydride and pyridine (1:1.5), overnight, at room temperature and under anhydrous conditions. The reaction was quenched by pouring the reaction mixture into ice. The aqueous solution was extracted with ethyl acetate, and the organic layer was washed with dilute HCl and brine and dried (Na2S04). Solvent was removed to give a gummy solid. This product was purified by silica gel chromatography u i n g chloroform-methanol (95:5) as the eluting solvent. The pure acetate derivative 6 (17.6. mg, yield 31%; oil, pure by 19C NMR and TLC on silica gel CHC13-MeOH, 91) was obtained: FABMS zyx 583 (M + H); IR (Kl3r) 3300, 2930, 1735, 1660, 1380, 980 cm-'; 'H NMR (CDCl,) zy B 6.3 (br, 1 H), 5.63 (br, 1 H), 5.57 (br s, 1 H), 5.03 (br s, 1 H), 5.0 (m, 1 H), 4.85 (dt, J = 2, 7 Hz, 1 H), 3.75 (m, 1 H), 3.65 (m, 1 H), 3.45 (t, J = 7 Hz, 2 H), 3.23 (dd, J = 7, 15 Hz, 2 H), 2.13 (s,3 H), 2.08 (s, 3 H), 2.01 (s, 3 H), 1.95 (s, 3 H), 1.2-1.7 (br, 30 H); 19CNMR (CDC13) (ppm) 21.03,21.33,23.14,23.34,26.82, 27.25,27.32,29.00, 29.12, 29.27, 29.29, 29.32, 29.36, 29.55, 31.93, 32.14, 34.05, 39.88, 39.88,42.32,43.33,52.10,56.22,70.66,74.35,164.75,168.15,169.25, 170.96, 171.24. Acknowledgment. We thank I. Gunnarsson for pro- viding fermentation broth and Dr. B. Pramanik for mass spectral data. Registry No. 1.HC1, 119948-40-2; 3, 119948-41-3; 4, 119948- 42-4; 5, 119948-43-5; 6, 119948-44-6. Sulfoxide Analogues of Dihydro- and Tetrahydroprephenate as Inhibitors of Prephenate Dehydratase John H. Bushweller and Paul A. Bartlett* Department of Chemistry, University of California, Berkeley, California 94720 Received October zyxwvuts 11. 1988 The sulfoxide derivatives 4-7 were prepared as analogues of tetrahydro- and dihydroprephenate, respectively, and a synthesis was attempted for 8, the prephenate mimic itself. As expected, the saturated analogues 4 and 5 were modest, reversible inhibitors (ICw/Km = 16 and 27, respectively) of prephenate dehydratase, the enzyme responsible for the Grob-type fragmentation of prephenic acid to phenylpyruvic acid. The unsaturated analogues 6 and 7 were envisaged as potential suicide substrates of the enzyme, if they could undergo an enzyme-induced Pummerer-typefragmentation. However, these compounds also proved to be modest, reversible inhibitors (IC,/Km = 29 and 21, respectively), and the synthesis of 8 failed because of apparent instability of this compound. The shikimic acid pathway is a key biosynthetic se- quence in plants and microorganisms, leading to the pro- duction of the aromatic amino acids as well as cofactor precursors and isoprenoid quinones.' This sequence has been a fertile area for investigation since it is replete with enzymatic transformations of unusual or unique mecha- nisms. In addition, the absence of this pathway in mam- mals and the success of the inhibitor glyphosate have made it an attractive target for herbicide development.2 Among the final steps in the biosynthesis of phenyl- alanine are the formal Claisen rearrangement of chorismic acid (1) to prephenic acid (2) and the Grob-type frag- mentation of the latter to phenylpyruvic acid (3). In 1 2 (1) Dewick, P. M. Nat. Prod. Rep. 1988,573-97. Floss, H. G. Recent Adu. Phytochem. 1986, 20, 13-55. Ganem, B. Tetrahedron 1978, 34, 3353-3383. Haslam, E. The Shikimate Pathway; Halstead Press: New York, 1974. (2) Amrhein, N. Recent Ado. Phytochem. 1986,20, 83-117. 0022-3263/89/ 1954-2404$01.50/0 Table I. Structural Comparison of Carbinols and Sulfoxides' Bond Lengths (A) c-c 1.51-1.52 C-S 1.78-1.80 C-OH 1.44-1.46 S-0 1.45-1.49 Bond Angles (deg) c-c-c 111-112 C-S-C 96-100 C-C-OH 107-1 11 C-S=O 105-108 -2 to -5 PK >S+-OH -1 to -3 ' C-OHZ' Escherichia coli, both of these steps are catalyzed by the bifunctional enzyme chorismate mutaselprephenate de- hydratase. Chemical modification: mutation: and kinetic studies5 all suggest that the active sites for the two ac- tivities are separate. The structure of prephenate and the presumed mecha- nism of the dehydratase reaction presented an opportunity to test an idea for inhibition of enzymes that promote the (5) Duggleby, R. G.; Sneddon, M. K.; Morrison, J. F. Biochemistry 1978, 17, 1548-1554. 0 1989 American Chemical Society