US 10,005,868 B2  64  63  Structures of Monomers 1 to 6 synthesized in Synthesis  Examples 1-1 to 1-6 are shown below.  0  Monomer 1  wherein Et denotes an ethyl group.  To a mixture of 120 g ofmethacrylic acid chloride, 300 g  of 17a-methylandrostan-17~-ol-3-one, and 1,500 g of tolu› ene was added 111 g of triethylamine while stirring under  ice-cooling. Thereafter, the mixture was stirred at room  temperature for 16 hours. The mixture was then subjected to  a usual aqueous post-treatment (aqueous work-up), and the  solvent was distilled off to obtain a crude product. The  product was purified by column chromatography to obtain  an intended product, Monomer 1.  Monomer 2 was synthesized in the same manner as in  Synthesis Example 1-1 except that 17a-methylandrostan- 17~-ol-3-one was changed to methyltestosterone.  Monomer 3 was synthesized in the same manner as in  Synthesis Example 1-1 except that 17a-methylandrostan- 17~-ol-3-one was changed to  ~-hydroxy-17-methylan› drosta-l,4-dien-3-one.  Monomer 4 was synthesized in the same manner as in  Synthesis Example 1-1 except that 17a-methylandrostan- 17~-ol-3-one was changed to  ~-hydroxy-17-methylan› drosta-4,9(11 )-dien-3-one.  Monomer 5 was synthesized in the same manner as in  Synthesis Example 1-1 except that 17a-methylandrostan- 17~-ol-3-one was changed to mestranol.  Monomer 1  X  0  Monomer 2  X  0  Monomer 3  X  0  Monomer4  X  0  Monomer 5  X  ’-----o  -continued  Monomer 6 was synthesized in the same manner as in  Synthesis Example 1-1 except that methacrylic acid chloride 65  was changed to methacrylic acid-5-carboxylic acid-4-oxatri- cyclo[ 4.2.1.0 $^{3}$.?]nonan-5-one-2-yl.  [Synthesis Example 1-3] Synthesis of Monomer 3  [Synthesis Example 1-2] Synthesis of Monomer 2  [Synthesis Example 1-4] Synthesis of Monomer 4  [Synthesis Example 1-5] Synthesis of Monomer 5  [Synthesis Example 1-6] Synthesis of Monomer 6 