Optimization of Potent, Selective, and Orally Bioavailable Pyrrolodinopyrimidine-Containing Inhibitors of Heat Shock Protein 90. Identification of Development Candidate 2-Amino-4-{4-chloro-2-[2-(4-fluoro-1 H -pyrazol-1-yl)ethoxy]-6-methylphenyl}- N -(2,2-difluoropropyl)-5,7-dihydro-6 H -pyrrolo[3,4- d ]pyrimidine-6-carboxamide