Preparation of Amylose-Oligo[(R)-3-hydroxybutyrate] Inclusion Complex by Vine-Twining Polymerization

In this study, we attempted to prepare an amylose-oligo[(R)-3-hydroxybutyrate] (ORHB) inclusion complex using a vine-twining polymerization approach. Our previous studies indicated that glucan phosphorylase (GP)-catalyzed enzymatic polymerization in the presence of appropriate hydrophobic guest polymers produces the corresponding amylose-polymer inclusion complexes, a process named vine-twining polymerization. When vine-twining polymerization was conducted in the presence of ORHB under general enzymatic polymerization conditions (45 °C), the enzymatically produced amylose did not undergo complexation with ORHB. However, using a maltotriose primer in the same polymerization system at 70 °C for 48 h to obtain water-soluble amylose, called single amylose, followed by cooling the system over 7 h to 45 °C, successfully induced the formation of the inclusion complex. Furthermore, enzymatic polymerization initiated from a longer primer under the same conditions induced the partial formation of the inclusion complex. The structures of the different products were analyzed by X-ray diffraction, ¹H-NMR, and IR measurements. The mechanism of formation of the inclusion complexes discussed in the study is proposed based on the additional experimental results.