Asymmetric synthesis of alanine using cobalt(III) complexes of (3R)-3-methyl-1,6-bis[(2S)-pyrrolidin-2-yl]-2,5-diazahexane and (3S)-3-methyl-1,6-bis[(2S)-pyrrolidin-2-yl]-2,5-diazahexane

Abstract

Upon decarboxylation Λ-cis-β-[COL¹(amm)]²⁺ yielded Λ-cis-β-[CoL²(R-alaO)]²⁺, while Δ-cis-β-[CoL²(amm)]²⁺ gave Δ-cis-β-[CoL²(S-alaO)]²⁺; where L¹=(3R)-3-methyl-1,6-bis[(2S)-pyrrolidin-2-yl]-2,5-diazahexane, L²=(3S)-3-methyl-1,6-bis[(2S)-pyrrolidin-2-yl]-2,5-diazahexane, amm =α-amino-α-methylmalonate and alaO = alaninate. The asymmetrically synthesized alanines were isolated but with extensive racemization via the decomposition of the decarboxylated complexes.