(±)-cis-4-[(2-Amino-4-chloro-6-pyrimidinyl)amino]-2-cyclopentene-1-methanol from Example 1 (11.58 g, 48.1 mmol) and sodium acetate trihydrate (97 g) were dissolved in glacial acetic acid (225 mL) and water (225 mL). A cold solution (0°-5° C.) of 4-chlorobenzenediazonium chloride was prepared from 4-chloroaniline (6.74 g, 52.8 mol), concentrated hydrochloric acid (14.7 mL) water (52 mL), and sodium nitrite (4.01 g, 58.2 mmol in 47 mL of water). This cold solution was added dropwise over 5 minutes to the first solution. The resulting yellow precipitate was filtered after 18 hours, washed with water, and extracted with ethanol to give title compound as dark yellow powder (12.56 g, 69%), m.p. 218°-220° C. dec.
