B#B.O=[C:4]1[CH2:21][S:20][CH2:19][CH2:18][S:17][CH2:16][C:15](=O)[NH:14][CH2:13][CH2:12][S:11][CH2:10][CH2:9][S:8][CH2:7][CH2:6][NH:5]1>O1CCCC1>[S:8]1[CH2:9][CH2:10][S:11][CH2:12][CH2:13][NH:14][CH2:15][CH2:16][S:17][CH2:18][CH2:19][S:20][CH2:21][CH2:4][NH:5][CH2:6][CH2:7]1A solution of diborane (20 ml.; 1.5 N) in anhydrous tetrahydrofuran is added dropwise to a suspension of 2 g. of the diamide obtained in Example 32 in 50 ml. anhydrous tetrahydrofurane under nitrogen at room temperature. The solid dissolves giving a clear solution. After the addition is completed the mixture is refluxed during four hours and a solid precipitate is formed. After cooling to room temperature, the excess reagent is destroyed by adding carefully 10 ml. of water. The solvents are evaporated to dryness and 6 N hydrochloric acid (50 ml.) is added to the solid residue. The mixture is refluxed for three hours: the solid does not dissolve, the mixture remaining heterogeneous. The mixture is evaporated to dryness and a solution of 10% sodium hydroxide in water (50 ml.) is added to the residue.
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