We also investigated solvent effects in the elimination of 2l and did not observe any formation of 4l even in protic solvents like HFIP. Instead, cyclization and subsequent elimination of the carbamate function to form 2-dehydropipecolic acid 6 was observed. The reaction in THF and toluene gave pipecolic acid 5l in 65% and 76%, respectively. To access the dehydrolysine 4l, we revisited the base-induced elimination. Using DBU in THF at 50 °C, we obtained the (Z)-isomer selectively in 43% yield.