To a solution of (4) (2.60 g., 11 mM) and 11-bromoundecanoic acid (2.65 g., 10 mM) in anhydrous methylene chloride (90 mL) is added 4-(dimethylamino)pyridine (1.22 g., 10 mM) followed by N,N'-dicyclohexylcarbodiimide (2.3 g., 11 mM) (4×5 mL of methylenechloride rinses). Precipitation of dicyclohexylurea (DCU) begins within 4 minutes. When TLC analysis indicates the reaction is complete, the mixture is filtered, the filtrate concentrated in vacuo and the residue extracted with ether. The combined ether extracts are washed 1× with 1N hydrochloric acid, 1× saturated sodium chloride solution, dried (Na2SO4) and concentrated to a residue which is stirred, filtered, and concentrated alternately with ether and methylene chloride until all DCU is removed. Concentration of the final solution yields the title product (32) (2.35 g.) as an oil that goes readily to a waxy solid.
