1H-Indole-1-carboxylic acid. 2-borono-5-[2-[[(1.1-dimethylethyl)dimethylsilyl]oxy]-3-[[2-[[(1.1-dimethylethyl)dimethylsilyl]oxy]ethyl]ethylamino]propoxy]-. 1-(1.1-dimethylethyl) ester