An Efficient synthesis of orthogonally protected trans‐ and cis‐4‐aminopipecolic acid

A straightforward synthesis of orthogonally N^α/N^γ‐protected trans‐ and cis‐4‐aminopipecolic acid is reported, starting from methyl cis‐4‐hydroxypiperidine‐2‐carboxylate. The two diastereomers were synthesized with the aid of C‐4 inversion (the trans isomer) or double C‐4 inversion (the cis isomer).