A solution of [2R diastereomer, N(1S)]-3-[4-[2-(phenoxazin-10-yl)ethoxy]phenyl]-2-ethoxy-N-(2-hydroxy-1-phenylethyl)propanamide (0.45 g, 0.84 mmol) obtained in example 21a in mixture of 1M sulphuric acid (17 mL) and dioxane/water (1:1, 39 mL) was heated at 90° C. for 88 h. The pH of the mixture was adjusted to 3.0 by addition of an aqueous sodium hydrogen carbonate solution. The mixture was extracted with ethyl acetate (2×25 mL) and the organic extract as washed with water (50 mL), brine (25 mL), dried (Na2SO4) and evaporated. The residue was chromatographed over silica gel using a gradient of 50-75% ethyl acetate in pet. ether to afford the title compound (0.2 g, 57%) as a white solid. mp: 77-78° C.
