reactants are commercially availlable.
schering corporation, wo2008/54702, a1, (2008) example 32preparation of intermediate compound 32aa mixture of 3-bromopyruvic acid (16.37 g, 98.05 mmol) in anhydrous dioxane (90 ml_) was treated with ethyl thioamidooxalate (13.08 g, 98.22 mmol) for 1.2 h at 50 0c, and was then concentrated at 50 0c to yield a dry yellow solid. the crude product was dissolved in saturated sodium bicarbonate (150 ml) and water (150 ml). this solution was extracte d with ethyl acetate (6 x 400 ml). the aqueous epo layer was then acidified to ph 2 with concentrated aqueous hci (21 ml_), resulting in the formation of a heavy precipitate. this suspen sion was extracted with ethyl acetate (5 x 500 ml_). these extracts were pooled, dried with sodium sulfate, filtered, concentrated, and dried for about 15 hours under vacuum to yield compound 32a as a red-brown solid (14.36 g, 73percent yield) which was used without further purification.
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