2-Alkoxy-5 -oxazolones mixed anhydrides

PURIFIED MIXED ANHYDRIDES OF N-ALKOXYCARBONYLAMINO ACIDS AND THEIR DECOMPOSITION TO 2-ALKOXY-5(4H)-OXAZOLONES... 

NL Benoiton, FMF Chen. Preparation of 2-alkoxy-5(4//)-oxazolones from mixed anhydrides of /V-alkoxycarbonylamino acids. Ini J Pept Prot Res 42, 455, 1993. 

FIGURE 7.6 Decomposition of a mixed anhydride (A) to the 2-alkoxy-5(4//)-oxazolone and the alkyl carbonate.9 The latter is in equilibrium with the anion whose reaction (B) with a second molecule of anhydride produces pyrocarbonate and the acid anion whose reaction (C) with a third molecule produces the symmetrical anhydride. The oxazolone eventually reacts with the alcohol to give the ester. (D) Acyloxonium ions formed by reaction of the anhydride with dimethylformamide and tetrahydrofuran. 

FIGURE 4.14 Reactions of activated A-alkoxycarbonylamino acids in the presence of tertiary amine. Acyl halides and mixed and symmetrical anhydrides generate 2-alkoxy-5(4/7)-oxazolone in the presence of tertiary amine. Aminolysis of 2-alkoxy-5(47f)-oxazolone in the presence of E N led to partially epimerized products. OAct = activating group. 

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