合成路线1

It is prepared by hydrolysis with ammonia in methanol of N-(3-acetylthio-2-methylpropanoyl)-L-proline (I). Compound (I) can be obtained in three different ways: 1) The reaction of L-proline tert-butyl ester (II) with 3-acetylthio-2-methyl-propanoic acid (III) by means of dicyclohexylcarbodiimide in CH2Cl2 gives N-(3-acetylthio-2-methylpropanoyl)-L-proline tert-butyl ester (IV), which is hydrolyzed with trifluoroacetic acid in anisole. 2) By condensation of L-proline (V) with 3-acetylthio-2-methylpropanoyl chloride (VI) (prepared from the corresponding acid (III) with SOCl2) by means of NaOH in water. 3) The condensation of L-proline (V) with methacryloyl chloride (VII) by means of NaHCO3 in water yields N-methacryloyl-L-proline (VIII), which is then treated with thiolacetic acid (A) and azobisisobutyronitrile. The acid (III) is obtained by addition of thiolacetic acid (IX) to methacrylic acid (X) at 100 C.