Compound (i) (50 mg, 0.1 mmol) was dissolved in acetonitrile (2 ml) and water (3 ml). Lithium hydroxide hydrate (8 mg, 0.2 mmol) dissolved in water (0.5 ml) was added. The reaction was complete after 0.5 h as determined by analytical HPLC. The mixture was acidified with TFA and purified by preparative RP-HPLC using acetonitrile and water containing 0.1% TFA as mobile phase. The appropriate fraction was concentrated in vacuo and the residue lyophilized from acetic acid to give the title compound as a white amorphous solid (27 mg, 48%). The substance is a diastereomeric mixture.
