n-Pentyl nitrite (98 g, 838 mM) is added over one hour at room temperature under nitrogen to a mixture of the compound of Example 2 (350 g, 819 mM), triphenylmethyl chloride (500 g, 1.79 M) and potassium carbonate (65 g) in CH2Cl2 (3 L). The resulting mixture is heated at reflux for 20 minutes, cooled to room temperature and filtered. The filtrate is concentrated in vacuo, and the resulting residue is purified by column chromatography on silica gel (2.5 kg, ethyl acetate/hexane 1:4-3:7) to yield the title compound as a pale yellow solid (272 g, 74%).
