Sustainable nitrogen-containing chemicals and materials from natural marine resources chitin and microalgae

N-Halogenation by Vanadium-Dependent Haloperoxidases Enables 1,2,4-Oxadiazole Synthesis

Nitrogen-containing compounds are valuable synthetic intermediates and targets in nearly every chemical industry. While methods for nitrogen-carbon and nitrogen-heteroatom bond formation have primarily relied on nucleophilic nitrogen atom reactivity, molecules containing nitrogen-halogen bonds allow for electrophilic or radical reactivity modes at the nitrogen center. Despite the growing synthetic utility of nitrogen-halogen bond-containing compounds, selective catalytic strategies for their synthesis are largely underexplored. We recently discovered that the vanadium-dependent haloperoxidase (VHPO) class of enzymes are a suitable biocatalyst platform for nitrogen-halogen bond formation. Herein, we show that VHPOs perform selective halogenation of a range of substituted benzamidine hydrochlorides to produce the corresponding N'-halobenzimidamides. This biocatalytic platform is applied to the synthesis of 1,2,4-oxadiazoles from the corresponding N-acylbenzamidines in high yield and with excellent chemoselectivity. Finally, the synthetic applicability of this biotechnology is demonstrated in an extension to nitrogen-nitrogen bond formation and the chemoenzymatic synthesis of the Duchenne muscular dystrophy drug, ataluren.

Novel study on catalytic pyrolysis of chitin biomass using waste cathode material recovered from spent Li-ion battery

Waste cathode (BC) from spent lithium-ion battery (LIB) was preliminarily studied for the catalytic pyrolysis of chitin biomass using thermogravimetric and pyrolysis-gas chromatography/mass spectrometry analysis. Compared with the dry-mixing method (BC1), the wet-impregnation method (BC2) significantly increased the decomposition rate of chitin pyrolysis and decreased the apparent activation energy from 85 kJ/mol to 76 kJ/mol. BC2 had a superior catalytic effect on the conversion of heavy components into light fractions. In particular, the selectivities for acetamides and acetonitrile were improved. Furthermore, BC2 enhanced the cleavage of glucosidic, C-O, and C-C bonds, thereby improving the thermolysis of chitin to acetamido acetaldehyde. The production of acetamides, acetonitriles, and other light components (e.g., ketones) was further enhanced via deoxygenation and hydrogenation reactions. Additionally, the selectivity of N-heterocycles (pyridine and pyrrole) and their derivatives (tar-N surrogates) decreased, indicating that tar was significantly reduced during the catalytic pyrolysis and gasification of chitin biomass.

Production of Nitrogen-Containing Compounds via the Conversion of Natural Microalgae from Water Blooms Catalyzed by ZrO2

Utilizing the inherent high nitrogen content in natural microalgae to produce value-added nitrogen-containing compounds such as fatty amides and fatty nitriles is a promising method. Herein, a method for producing value-added fatty amides and nitriles by liquefaction of natural microalgae from water blooms in n-heptane was developed. The effects of temperature, metal oxide catalyst (ZrO₂ , Al₂ O₃ , TiO₂ , ZnO, MgO, CaO), catalyst amount, and reaction time on the preparation of value-added nitrogen-containing compounds were studied. Under the optimized conditions (0.3 g ZrO₂ , 300 °C, 6 h), the total yield of fatty amides was 6.9 wt %, and the yield of fatty nitriles was 1.9 wt %. Compared with the results obtained in the absence of ZrO₂ , after adding ZrO₂ the total yield of fatty acids was reduced by 4.7 wt % (18.5 to 13.8 wt %), while the total yield of fatty amides only increased by 0.9 wt % (6.0 to 6.9 wt %) and fatty nitriles was increased by 1.5 wt % (0.4 to 1.9 wt %). Exploring the role of ZrO₂ by using model compounds (i. e., palmitic acid and palmitamide) revealed that ZrO₂ could promote the dehydration of fatty amides to form fatty nitriles, but had limited effect on the reaction of fatty acid and NH₃ .

Chemoenzymatic access to enantiopure N-containing furfuryl alcohol from chitin-derived N-acetyl-D-glucosamine

BACKGROUND

Chiral furfuryl alcohols are important precursors for the synthesis of valuable functionalized pyranones such as the rare sugar L-rednose. However, the synthesis of enantiopure chiral biobased furfuryl alcohols remains scarce. In this work, we present a chemoenzymatic route toward enantiopure nitrogen-containing (R)- and (S)-3-acetamido-5-(1-hydroxylethyl)furan (3A5HEF) from chitin-derived N-acetyl-D-glucosamine (NAG).

FINDINGS

3-Acetamido-5-acetylfuran (3A5AF) was obtained from NAG via ionic liquid/boric acid-catalyzed dehydration, in an isolated yield of approximately 31%. Carbonyl reductases from Streptomyces coelicolor (ScCR) and Bacillus sp. ECU0013 (YueD) were found to be good catalysts for asymmetric reduction of 3A5AF. Enantiocomplementary synthesis of (R)- and (S)-3A5HEF was implemented with the yields of up to  >  99% and the enantiomeric excess (ee) values of  >  99%. Besides, biocatalytic synthesis of (R)-3A5HEF was demonstrated on a preparative scale, with an isolated yield of 65%.

CONCLUSIONS

A two-step process toward the chiral furfuryl alcohol was successfully developed by integrating chemical catalysis with enzyme catalysis, with excellent enantioselectivities. This work demonstrates the power of the combination of chemo- and biocatalysis for selective valorization of biobased furans.