Stereoselectivity in Reactions of Metal Complexes. Part XVII. Synthesis of three new optically active triamines: 2, 6‐Bis (2S) ‐2‐ (hydroxymethyl) pyrrolidin‐1‐ylmethylpyridine, 2, 6‐bis (2S) ‐2‐ (methoxymethyl) pyrrolidin‐1‐ylmethylpyridine, and 2, 6‐bis{ (2S) ‐2‐ (benzyloxy) methylpyrrolidin‐1‐ylmethyl}pyridine. X‐ray structure and equilibrium behaviour of their copper (II) complexes