[CH3:1][C:2]1[O:3][C:4]([CH2:13][CH:14](C(OCC)=O)[C:15]([O:17]CC)=[O:16])=[C:5]([C:7]2[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=2)[N:6]=1>C(O)(=O)C.Cl>[CH3:1][C:2]1[O:3][C:4]([CH2:13][CH2:14][C:15]([OH:17])=[O:16])=[C:5]([C:7]2[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=2)[N:6]=1Diethyl 2-(2-methyl-4-phenyl-5-oxazolylmethyl)malonate (8.0 g) was dissolved in a mixture of acetic acid (50 ml) and 6N hydrochloric acid (20 ml) and the solution was refluxed with stirring for 3 hours. The solvent was then distilled off and the residue was made alkaline with 2N sodium hydroxide and washed with ethyl ether. The alkaline solution was adjusted to pH 2 with concentrated hydrochloric acid to give 2-methyl-4-phenyloxazole-5-propionic acid as crystals, yield 4.85 g (overall yield from the 5-bromomethyl compound=57.5%). Recrystallization from ethanol gave colorless prisms, yield 3.40 g (overall yield from the bromomethyl compound=40.3%), m.p. 156°-157° C.
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