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3A.1
Stepl:An aqueous solution of the dicyclohexylamine salt of compound 3a1 (0.5 g, 1.12mmol) was adjusted to pH 2 by addition of 1M HCI and the resulting aqueous phasewas extracted twice with EtOAc. The EtOAc phase was dried (MgSO4), filtered andconcentrated) to give 290 mg (1.10 mmol, 98%) of the free acid. The free acid wasdissolved in 4M HCI/dioxane (5 ml_) and the mixture was stirred at room temperaturefor 1 hour. The solvent was evaporated and the residue 3a2 was dried under vacuumand used as is in the next step.