[N:1]1([S:6]([CH2:9][CH2:10][CH2:11][N:12]2C(=O)C3C(=CC=CC=3)C2=O)(=[O:8])=[O:7])[CH2:5][CH2:4][CH2:3][CH2:2]1.[BH4-].[Na+].C(O)(=O)C>C(O)(C)C.O.CO>[N:1]1([S:6]([CH2:9][CH2:10][CH2:11][NH2:12])(=[O:7])=[O:8])[CH2:2][CH2:3][CH2:4][CH2:5]1
A solution of Intermediate 27 (0.139 g) in isopropanol (7.6 ml) and water (1.3 ml) was treated with sodium borohydride (0.081 g), and the mixture was stirred at room temperature under nitrogen for 19 h. Glacial acetic acid (0.45 ml) was added cautiously and the mixture heated at 80° C. for 2 h. The solvents were evaporated in vacuo to give a white solid, which was dissolved in methanol and applied to a sulphonic acid ion exchange cartridge (10 g Isolute SCX). Elution with methanol followed by 10% 0.880 ammonia in methanol, and evaporation of the ammonia/methanol fraction gave the title compound as a white solid (0.027 g).
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