Synthesis of an enantiomer of cellulose via cationic ring-opening polymerization
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ORIGINAL RESEARCH
Synthesis of an enantiomer of cellulose via cationic ringopening polymerization Takahiro Yagura . Waki Ikegami . Hiroshi Kamitakahara
. Toshiyuki Takano
Received: 2 September 2020 / Accepted: 4 October 2020 Ó Springer Nature B.V. 2020
Abstract The enantiomer of natural ‘‘D-cellulose’’ (= ‘‘L-cellulose’’), which consists of L-glucose, was synthesized from L-glucose via cationic ring-opening polymerization. L-Glucose (1L) was converted to 3-Obenzyl-2,6-di-O-pivaloyl-b-L-glucose 1,2,4-orthopivalate (6L) by five reaction steps. L-Glucose and its derivatives showed almost the same reactivity as Dglucose and its derivatives during the synthesis of compound 6L. Cationic ring-opening polymerization of compound 6L under atmospheric pressure proceeded smoothly to give 3-O-benzyl-2,6-di-O-pivaloyl-b-L-glucopyranan (7L) with a degree of polymerization (DPn) of 32.8 (Mw/Mn = 2.19). Removal of the benzyl and pivaloyl groups of compound 7L and subsequent acetylation gave acetylated b-L-glucopyranan. 1H and 13C NMR spectra of the acetylated b-L-glucopyranan had the same profiles as those of commercial cellulose triacetate prepared from natural cellulose, while its specific rotation was opposite, indicating the successful synthesis of L-
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10570-020-03512-z) contains supplementary material, which is available to authorized users. T. Yagura W. Ikegami H. Kamitakahara T. Takano (&) Division of Forest and Biomaterials Science, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan e-mail: [email protected]
cellulose. The synthesized L-cellulose had a cellulose II crystal structure. This is the first reported synthesis of L-cellulose, an L-polysaccharide that consists of an L-monosaccharide. Keywords Chirality Enantiomer L-Cellulose LSugar Stereoisomer
Introduction In nature, D-sugars are generally found in natural products because of the low abundance of L-sugars. Cellulose, which is the main constituent of the plant cell wall and the most abundant polymer in nature, is a linear homopolymer consisting of D-anhydroglucose units (hereafter ‘‘D-cellulose’’). Much attention has been paid to high-value added D-cellulose utilization although D-cellulose is widely used in our daily life. One important property of D-cellulose for such utilization is chirality. Indeed, D-cellulose derivatives for chiral separation (Francotte 1994, Okamoto and Yashima 1998, Yamamoto and Okamoto 2004, D’Orazio et al. 2018, Chankvetadze 2020), chiral nematic D-cellulose liquid crystalline (Nishio et al. 2016), and D-cellulose-based organocatalysts for asymmetric synthesis (Yasukawa et al. 2015; Ranaivoarimanana et al. 2019) have been proposed and put to partial practical use. However, the effect of
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Cellulose
the chirality of D-cellulose on the applications was not well understood. L-Glucose, an enantiomer of D-glu
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