Synthetic analogs: Syndiotactic Poly(3-hydroxybutyrate)
Our laboratory discovered that when tin-based catalyst systems are used to catalyze ring-opening polymerizations of racemic b-butyrolactone, the result is predominantly syndiotactic poly(3-hydroxybutyrate). The importance of this finding is due to that its stereoregular isomer, isotactic and enantiopure poly([R]-3-hydroxybutyrate), is found ubiquitously in nature. Syndiotactic analogs of bacterial poly(3-hydroxybutyrate) were found to degrade at unexpectedly rapid rates in the presence of some depolymerase enzymes that degrade the corresponding isotactic enantiopure polyester. These findings stimulated a number of other laboratories to begin research on this new polymer type that had very different stereoisomer of bacterial poly(3-hydroxybutyrate).
Scheme 22. A mechanism for the initiation and propagation steps of syn-PHB synthesis from (R,S)-BL using the Sn(n-Bu3)3(OCH3) catalyst system.
References
- John E. Kemnitzer, Stephen P. McCarthy, Richard A. Gross, John Liggat, DavidJ. Blundell and Mike Cox, "Crystallization Behavior of Predominantly Syndiotactic Poly(β-hydroxybutyrate)", J. Environ. Polym. Deg. Vol. 3(1), 37-47 (1995).(PDF)
- John E. Kemnitzer, Stephen P. McCarthy, and Richard A. Gross, "Syndiospecific Ring-Opening Polymerization of β-Butyrolactone to Form Predominantly Syndiotactic Poly(β-hydroxybutyrate) Using Tin (IV) Catalysts", Macromolecules, Vol. 26, 6143-6150 (1993).(PDF)
- John E. Kemnitzer, Stephen P. McCarthy, and Richard A. Gross, "The Preparation of Predominantly Syndiotactic Poly(β-hydroxybutyrate) by the Tributyl Methoxide Catalyzed Ring-Opening Polymerization of Racemic β-Butyrolactone " Macromolecules, Vol. 26, pgs. 1221-1229 (1993).(PDF)