An LDA solution was prepared by treating diisopropylamine (6.98 g, 69 mmol) with BuLi (1.6 M, 41.3 mL, 66 mmol) at −78° C. in dry THF (45 mL) under argon and allowing to warm up to −20° C. This solution was then cooled to −60° C. added to a solution of piperidine-1,4-dicarboxylic acid 1-tert-butyl ester 4-ethyl ester (15.44 g, 60 mmol) in dry THF (45 mL) at −60° C. and allowed to warm up to −40° C. over 1 h whereupon a solution of 4-fluoro-trans-beta-nitrostyrene (10.02 g, 60 mmol) in dry THF (40 mL) was added dropwise. The reaction mixture was allowed to warm up to room temperature over 1 h and then quenched with ammonium chloride (saturated, 250 mL) and the product extracted with diethylether (3×100 mL). The combined organic extracts were then washed with brine, dried over sodium sulfate, filtered and evaporated to afford the title compound (26.7 g, 99%) as a light yellow gum. MS: m/e=442.4 (M+NH4).
