ASYMMETRIC SYNTHESIS OF PROLINE USING COBALT(III)-TETRAAMINE COMPLEXES

Abstract

The decarboxylation reaction of δ -cis-β-Co(L₁)(pdH)]²⁺ complex yielded δ -cis-β-Co(L₁) (R-pro)]²⁺, while the δ -cis-β-Co(L₂) (S-pro)]²⁺ was obtained from the reaction of δ -cis-β-Co(L₂) (pdH)]²⁺, where L₁ is (3R)3-methyl-1, 6-bis(2S)-pyrrolidin-2-yl]-2, 5-diazahexane, L₂ is (3S) 3-methyl-1, 6-bis-(2S)-pyrrolidin-2-yl]-2, 5-diazahexane, and pdH is the pyrrolidine-2, 2-dicarboxylate ion. The asymmetrically synthesized prolines were isolated via the decomposition of the decarboxylated complexes. The proline isolated from δ -cis-β-Co(L₁) (R-pro)]²⁺ showed a specific rotation of +12.0, representing a 24% excess of R-proline over S-proline, while the proline isolated from δ -cis-β-Co(L₂) (S-pro)]²⁺ showed a specific rotation of -10.0, indicating a 20% excess of S-proline over R-proline.