Ephedrine, polymer-based

Stereoselective reduction of a,(i-unsaturated ketones using lithium aluminium hydride has only been reported in conjunction with the ephedrine bases either in a two-phase system (80-90% yield, ee >70%) or immobilized on a polymer [18, 19]. 

As early as 1904, Willstatter attempted to separate optical isomers on the optically active natural polymers wool and silk [10]. About 35 years later, the first partial chromatographic resolution of the enantiomers ofp-phenylene-bis-imino-cam-phor on lactose was achieved by Henderson and Rule [11], and a few years later by Lecoq for the enantiomers of ephedrine [12], and by Prelog and Wieland for the enantiomers ofTroeger s base [13]. 

It is interesting to note that computer simulation can also be used to mimic real chromatographic experiments. For example, the interaction of the methacrylic acid based polymer with the HCl salt of ephedrine (binding energy of MA with ionized ephedrine is —22.48 kcal/mol) which is much stronger, k 7.3, than its interaction with... 

A new strategy for optically active chiral polymers was envisaged and based on a Suzuki coupling polymerisation of (li ,2 S)-ephedrine unit-bearing monomer with rigid linkers [129], The Suzuki coupling of ephedrine-derived dibromide 163 (which was prepared in four steps from (17 ,25)-ephedrine) with the diboronic acid 164 in presence of Pd(PPh3)4 afforded chiral... 

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