The condensation of benzophenone (I) with chloroacetic acid methyl ester (II) by means of sodium methoxide in THF gives the epoxide (III), which is treated with methanol/BF3.Et2O, yielding 2-hydroxy-3-methoxy-3,3-diphenylpropionic acid methyl ester (IV). The condensation of (IV) with 4,6-dimethoxy-2-(methylsulfonyl)pyrimidine (V) by means of K2CO3 in DMF affords 2-(4,6-dimethoxypyrimidin-2-yloxy)-3-methoxy-3,3-diphenylpropionic acid methyl ester (VI), which is hydrolyzed with NaOH in hot dioxane/water to give the corresponding free acid (VII). Finally, this compound is submitted to optical resolution, affording LU-135252. Optical resolution of (VIII), the free acid derivative of (IV), with (R)-phenylethylamine, L-proline methyl ester, (S)-1-(4-nitrophenyl)ethylamine or (S)-1-(4--chlorophenyl)ethylamine leads to the enantiomerically pure (S)-enatiomer (IX), which by reaction with 4,6-dimethoxy-2-(methylsulfonyl)pyrimidine (V) directly affords LU-135252.
The condensation of benzophenone (I) with methyl 2-chloroacetate (II) by means of NaOMe in THF gives 3,3-diphenyloxirane-2-carboxylic acid methyl ester (III), which by treatment with BF3/Et2O and methanol, followed by optical resolution, yielded the pure enantiomer 2(S)-hydroxy-3-methoxy-3,3-diphenylpropionic acid methyl ester (IV). The condensation of (IV) with 4,6-dimethyl-2-(methylsulfonyl)pyrimidine (V) by means of K2CO3 in DMF affords 2-(4,6-dimethylpyrimidin-2-yloxy)-3-methoxy-3,3-diphenylpropionic acid methyl ester (VI), which is finally hydrolyzed with KOH in hot dioxane to afford the target propionic acid as a racemic mixture.
A pilot plant process was further developed for the (S)-enantiomer. Darzens condensation of benzophenone (VIII) with methyl chloroacetate gave the glycidic ester (X). Epoxide opening in (X) with trimethylaluminum furnished methyl 2-hydroxy-3,3-diphenylbutyrate (XI), which was hydrolyzed to the corresponding acid (VI) by using KOH in isopropanol. Treatment of the racemic acid (VI) with (S)-1-(4-chlorophenyl)ethylamine (XII) provided the desired (S)-acid salt (XIII). This was finally condensed with 4,6-dimethyl-2-(methylsulfonyl)pyrimidine (XIV) in the presence of lithium amide to yield the title compound.