Citric Acid → (E)-3-{1'-tert-butoxycarbonyl-3,4-dihydro-4-oxo-spiro[2H-(1,3)-benzoxazine-2,4'-piperidin]-6-yl}-acrylic acid

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Reaction Steps

(E)-3-{1′-Tert-butoxycarbonyl-3,4-dihydro-4-oxo-spiro[2H-(1,3)-benzoxazine-2,4′-piperidin]-6-yl}-acrylic acid methyl ester (obtained as described in Example 25, Step A, 300 mg, 0.745 mmol) was treated with 1 M NaOH following the procedure described in Example 71, Step B, using citric acid instead of hydrochloric acid giving (E)-3-{1′-tert-butoxycarbonyl-3,4-dihydro-4-oxo-spiro[2H-(1,3)-benzoxazine-2,4′-piperidin]-6-yl}-acrylic acid (287 mg, 99%). The resulting product was treated with NH2OTHP according to the procedure described in Example 71, Step C, giving (E)-3-{1′-tert-butoxycarbonyl-3,4-dihydro-4-oxo-spiro[2H-(1,3)-benzoxazine-2,4′-piperidin]-6-yl}-N-(tetrahydro-pyran-2-yloxy)-acrylamide. Finally, removal of the THP and BOC protecting groups following the procedure described in Example 71, Step C gave (E)-3-{3,4-dihydro-4-oxo-spiro[2H-(1,3)-benzoxazine-2,4′-piperidin]-6-yl}-N-hydroxy-acrylamide hydrochloride (109 mg) as a white solid.

Provenance & Evidence