[OH:1][C:2]1[S:3][C:4](=[O:7])[NH:5][N:6]=1.C([O-])(O)=O.[Na+].Br[CH2:14][CH2:15][CH2:16][CH2:17][CH2:18][CH2:19][C:20]([O:22][C:23]([CH3:26])([CH3:25])[CH3:24])=[O:21].CCOCC>CN(P(N(C)C)(N(C)C)=O)C.[Na+].[I-]>[C:23]([O:22][C:20](=[O:21])[CH:19]=[CH:18][CH2:17][CH2:16][CH2:15][CH2:14][N:6]1[NH:5][C:4](=[O:7])[S:3][C:2]1=[O:1])([CH3:26])([CH3:25])[CH3:24]A solution of 11.8 g (0.1 mole) of 1,3,4-thiadiazoline-2,5-dione (1) (Example 1A) in 75 ml of HMPA was stirred with 9.24 g (0.11 mole) of NaHCO3 at room temperature for 18 hrs and then 0.3 g NaI was added followed by 26.5 g (0.1 mole) of tert-butyl 7-bromoheptanoate which was added dropwise over a period of 2 hr. The reaction mixture was stirred at room temperature for 5 days then poured with stirring into 500 ml of ice-cold 5% HCl topped with 200 ml of ether. The ether phase was washed with water and then with three 100-ml portions of 2.5% NaHCO3. The combined NaHCO3 solutions were washed with fresh ether, topped with 200 ml of fresh ether, and while being cooled in ice, acidified by dropwise addition of conc. HCl to pH 2-3. The ether layer was drawn off, two more ether extractions of the aqueous layer were made, and the combined ether extract was washed once with satd. NaCl, dried over Na2SO4, and evaporated. 2,5-Dioxo-1,3,4-thiadiazoline-3-heptanoic acid tert-butyl ester (6.58 g, 22%) was obtained as an oil, IR, (neat) νmax 1735 and 1725 (CO2 t-Bu), and 1675 cm-1 (amide), pmr, (CDCl3, TMS) δ 8.70 (s,1H,OH,NH), 3.75 (t, 2H, NCH2), 2.22 (t, 2H, CH2CO2), and 1.45 ppm (s, 9H C(CH3)3).
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