“Furan Endwise Peeling” of Celluloses: Mechanistic Studies and Application Perspectives of a Novel Reaction

Abstract

The mechanism of a novel reaction type, the “furan endwise peeling” reaction, has been studied. Making extensive use of experiments on model compounds, the structural prerequisites to the reaction were found to be a 2‐hydroxpyran β‐glycosidically linked to a 2‐(2‐furyl)ethyl moiety. Proceeding from the reducing end of the celluloses, the reaction causes the one‐by‐one loss of anhydroglucose units (AGUs) which are concomitantly converted into 2‐(tetrahydroxybutyl)furans (4) by co‐reacting with 1,3‐dicarbonyl compounds such as ethyl acetoacetate (1). The key step of the reaction is the formation of a furan at the reducing end followed by the attack of the 2‐OH group of the last‐but‐one AGU at this terminal furan. The intermediate, unstable dioxepane fragments by cleavage of the glycosidic bond. The terminal AGU is released as a substituted furan, the “new” reducing end reacting immediately with the 1,3‐dicarbonyl component to form a new terminal furan which, in turn, undergoes the same cycle. The “furan endwise peeling” reaction represents an interesting way to convert cellulosic biomass by an easy procedure into substituted furans that are valuable fine chemicals with multiple uses.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Cellulose‐based graft copolymers with controlled architecture prepared in a homogeneous phase

“…High acylation efficiencies showed that the dioxane‐based activation represents an excellent alternative to the established methods. In addition, it leads to clear and colorless cellulose solutions, as opposed to those prepared using the thermal activation, where at least a small extent of degradation is likely to take place, resulting in yellowish or amber solutions 29, 40–42. A detailed discussion of the use of dioxane‐based activation method in the dissolution of different cellulose pulps, physicochemical analysis of the activated samples, and comments on the activation mechanism will be the subject of a forthcoming separate report.…”

Chemoenzymatic Synthesis of β‐D‐Glucosides using Cellobiose Phosphorylase from Clostridium thermocellum

“…2‐Phenylethyl β‐ D ‐glucopyranoside: 41 1 H NMR (CD 3 OD): δ =2.941 (1 H, m, Σ J =25.0 Hz, H‐2′u), 2.973 (1 H, m, Σ J =25.0 Hz, H‐2′d), 3.205 (1 H, dd, J =9.2, 7.8 Hz, H‐2), 3.286 (1 H, m, H‐5), 3.305 (1 H, m, H‐4), 3.369 (1 H, dd, J =9.2, 8.6 Hz, H‐3), 3.684 (1 H, dd, J =11.9, 5.5 Hz, H‐6u), 3.779 (1 H, ddd, J =9.7, 8.2, 6.7 Hz, H‐1′u), 3.882 (1 H, dd, J =11.9, 2.1 Hz, H‐6d), 4.111 (1 H, ddd, J =9.7, 8.2, 6.8 Hz, H‐1′d), 4.322 (1 H, d, J =7.8 Hz, H‐1), 7.197 (1 H, m, H‐ para ), 7.267 (4 H, m, H‐ ortho , H‐ meta ); 13 C NMR (CD 3 OD): δ =37.53 (C‐2′), 63.05 (C‐6), 71.94 (C‐4), 72.01 (C‐1′), 75.40 (C‐2), 78.26 (C‐5), 78.40 (C‐3), 104.68 (C‐1), 127.50 (C‐ para ), 129.64 (C‐ meta ), 130.32 (C‐ ortho ), 140.36 (C‐ ipso ); MS (ESI): m/z =307.1152 [M+Na] + , calcd. mass for C 14 H 20 O 6 Na: 307.1152.…”

Triterpene Saponins from <i>Clethra barbinervis</i> and Their Hyaluronidase Inhibitory Activities

“…3) In this paper, seven new saponins (1-4, 6-8) and a new lignan glucoside (14) were isolated from the extract of C. barbinervis, together with echinocystic acid 3-β-d-glucuronopyranoside (5), 4) hemsganoside B (9), 5,6) scheffleraside II (10), 5) rotundic acid (11), 7) barbinervic acid (12), 8) clethric acid (13), 9,10) 8-O-4′ neolignan 7-O-β-glucopyranoside (15), 11) rourinoside (16), 12) epicatechin (17), 13) pavetannin A (18), 14) 2-phenylethyl β-glucopyranoside (19), 15) 2-phenylethyl O-α-larabinofuranosyl-(1→ 6)-β-d-glucopyranoside (20), 16) 2-phenylethyl O-α-l-rhamnopyranosyl-(1→ 6)-β-d-glucopyranoside (21), 17) and methyl salicylate β-primeveroside (22) 18) (Figs. 1, 2).…”

“…Fractions 2A (90.1%, 2.0 mg/mL), 2C (68.0%, 2.0 mg/mL), 2D (78.9%, 2.0 mg/mL), and 2E (71.7%, 2.0 mg/mL) separated from 1C (91.4%, 2.0 mg/mL) had high inhibitory activities. Nine constituents (14)(15)(16)(17)(18)(19)(20)(21)(22) were isolated from 2A, and 17 was active (IC 50 0.94 mm). Catechins are already known to have hyaluronidase inhibitory activity.…”