(−)‐Sparteine: The compound that most significantly influenced my research

Abstract

A chiral diamine alkaloid, (−)‐sparteine (Sp), has been found to be very effective as a ligand for Grignard reagents when used for the enantiomer‐selective polymerization of racemic RS‐1‐phenylethyl methacrylate. The enantiomeric excess of the initially polymerized monomer is 93%, and at about a 60% conversion, nearly optically pure R‐monomer is recovered. This enantiomer selectivity is today the highest in polymer chemistry. Triphenylmethyl methacrylate (TrMA) is a unique monomer that gives a highly isotactic polymer even during radical polymerization. When TrMA is polymerized with the Sp complex with n‐butyllithium in toluene at −78 °C, an optically active, isotactic polymer [poly(triphenylmethyl methacrylate) (PTrMA)] with a one‐handed helical conformation is obtained. The helical structure is maintained even at room temperature in solution. Analogous helical polymethacrylates that show various conformational changes have also been found. One‐handed helical PTrMA exhibits high chiral recognition to a variety of racemates as a chiral stationary phase (CSP) for high‐performance liquid chromatography. This finding has led to the development of very powerful CSPs based on polysaccharides, such as cellulose and amylose. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4480–4491, 2004

Supramolecular Helical Systems: Helical Assemblies of Small Molecules, Foldamers, and Polymers with Chiral Amplification and Their Functions

“…Since the first helical vinyl polymer (PTrMA) with a one-handed static helical conformation was prepared by the helix-sense-selective anionic polymerization of achiral triphenylmethyl methacrylate using chiral anionic initiators by Okamoto et al, various achiral methacrylates bearing other bulky substituents have been designed and synthesized to find effective structures for helix-sense-selective polymerizations. ,, However, such structures were limited to the triarylmethyl substituents or their analogues. Recently, Kamigaito and co-workers reported the asymmetric anionic polymerization of a novel methacrylate bearing an extremely bulky tris­(trimethylsilyl)­silyl group ( 396 ) to produce an optically active polymer with a prevailing one-handed helical conformation (Figure A) .…”

Efficient Separation of Enantiomers Using Stereoregular Chiral Polymers

“…The resolution of another chiral polymer, poly­[( R )- and ( S )-1-phenylethyl methacrylate], was also performed by Hatada and Yuki using the one-handed helical polychloral in 1981 . Due to their excellent recognition abilities for numerous compounds, the Pirkle column and the PTrMA column were commercialized from Regis in 1981 and Daicel in 1982, respectively. In 1984, two CSPs based on stereoregular natural polymers, cellulose tribenzoate and trisphenylcarbamate, were developed by Okamoto et al , and Daicel, and four types of cellulose-based CSPs, including the above-mentioned two CSPs, were commercialized from Daicel.…”

Precision synthesis, structure and function of helical polymers

“…This review summarizes our achievements over 35 years with respect to the synthesis and chiral recognition of the helical polymers obtained by the helix-sense-selective polymerization of bulky methacrylates and by the modification of polysaccharides, cellulose and amylose. 9 , 10 )…”