| 摘要 |
A process for preparing a compound of formula (I) comprising reacting a compound of formula (II), at a pH range of between about 7 and about 11, to form a compound of formula (III) wherein R5 is N-t-butoxycarbonyl, reacting a compound of formula (III) with at least 0.5 equivalents of (lR, 2S)- (-) ephedrine, in an alkyl acetate solvent, to form a salt of formula (IV) wherein Ph is phenyl, reacting the salt of formula (IV) with an inorganic base in water to form a carboxylate salt of the compound of formula (V), acidifying the carboxylate salt of the compound of formula (V) with an acid of pKa less than or equal to three, to a pH of between about 3.5 and about 6.5, to form the compound of formula (V), reacting the compound of formula (V), at a temperature less than about25 C, to form the compound of formula (I).
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