ammonium chloride and extracted with diethylether 2 u00d7 300 ml the organic layer was washed with brine dried over sodium sulfate and concentrated under vacuum the crude residue was purified by silica gel column chromatography using hexane diethyl ether 9 1 as the eluant to obtain 1 16 g 1 82 mmol 32 yield of pure mono alkylated product 37 as a colorless oil 1 h nmr cdcl 3 200 mhz u03b4 0 88 t 3h j 6 2 hz 1 04 s 9h 1 25 bs 24h 1 43 s 9h 1 76 u2013 1 89 m 4h 2 64 td 2h j 7 3 4 4 hz 3 13 t 1h j 7 3 hz 3 66 t 2h j 6 0 hz 7 34 u2013 7 43 m 6h 7 62 u2013 7 67 m 4h ms fab m z 581 m h isobutene 563 m u2212 tbuo synthesis of thiouracil 16 a solution containing alkylated u03b2 ketoester 37 1 16 g 1 82 mmol in absolute ethanol 24 ml in a screw cap sealed vial was treated first with 0 19 g 2 6 mmol of thiourea and then with 0 25 g 2 0 mmol of potassium tert butoxide the resulting solution was stirred at 100 u00b0 c for 6 hours the solvent was then removed under vacuum the residue was diluted with water and neutralized to ph 6 u2013 7 with.