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Aldol condensation of 5-hydroxymethylfurfural (HMF) with acetone provides a route to upgrading of biomass intermediates into value-added compounds such as fuel precursors. This reaction gives C9 and C15 aldol adducts. These adducts can be further converted to jet fuel additives on hydrogenation and hydrodeoxygenation. Herein, we report a novel catalyst, namely, aluminum-exchanged heteropolyacid encapsulated inside the cage of ZIF-8 (Al0.66-DTP@ZIF-8) (DTP = dodecatungstophosphoric acid; ZIF = zeolitic imidazolate framework) for selective synthesis of C9 adducts. The acidic nature of the catalyst gives a maximum conversion of HMF (99%) in 10 h, and the smaller pore diameter of ZIF-8 leads to the highly selective formation of C9 adducts (84.11%). The fresh and spent catalysts were characterized by various techniques. A kinetic model was developed, and the apparent activation energy for both monomer and dimer formations was calculated. Recyclability of catalyst was studied up to four cycles, and the catalyst was observed to be stable and reusable.

No abstract

Raspberry ketone, also called as rheosmin, is an important flavor compound used in perfumery and food industry. In the current work, it was synthesized from p‐hydroxybenzaldehyde (PHB) and acetone in one pot system. Crossed aldol condensation of p‐hydroxybenzaldehyde gave α,β‐unsaturated ketone, i. e. p‐hydroxybenzalacetone (PHBA) which was further reduced to obtain raspberry ketone. Mixed oxide catalysts of different combinations of Mg, La and Zn were prepared by three different methods such as hydrothermal, combustion and co‐precipitation. Among all Zn−La with mole ratio 3:1, synthesized by combustion method and glycine as fuel, gave the best results for selective synthesis of PHBA. For hydrogenation of PHBA, Ni, Cu and Pd metals were screened to find that 2% Ni/Zn3:La1 was the best catalyst for one‐pot synthesis of raspberry ketone. It showed excellent textural properties like high surface area (680 m2/g), activity and selectivity. The virgin and spent catalyst samples were fully characterized by SEM, TEM, TGA, FTIR, CO2 and NH3‐TPD and BET surface area analysis. It was stable, active and reused for 4 cycles. The kinetic model was developed separately for two different steps. The reaction is kinetically controlled with activation energy of 18.48 kcal/mol for crossed aldol condensation and 14.19 kcal/mol for hydrogenation step. It is an interesting example of process chemistry and engineering using a novel catalyst and process.

The resistivity of plant pathogen Erwinia amylovora against the polymyxin group of antibiotics is enhanced by modification of lipid A from lipopolysaccharide with 4-amino-4-deoxy L-arabinose (Ara4N) catalyzed by a bifunctional protein ArnA. ArnA is the first enzyme in the lipid A modification pathway with distinct dehydrogenase and transformylase domains which has been known in development of resistivity to polymyxin group of antibiotics. Thus, three dimensional structure of ArnA protein from Erwinia amylovora was constructed using homology modeling technique. The quality and reliability of the generated 3-D model was then assessed by different online available programs such as What if, PROCHECK, QMEAN, ProSA along with superimposition by UCSF Chimera. Sequence analysis study of ArnA protein from E. coli, Erwinia amylovora, Yersinia pestis, Ps. aeruginosa and Salmonella showed conserved domains with exact active site residues. Molecular docking study of ArnA protein with substrate UDP-GlcA and different inhibitors such as 5-formyl-5,6,7,8 tetrahydrofolate, leucovorin and 5-methyl tetrahydrofolate revealed similar binding pocket. The residues ASN492, ARG510, SER433 and ARG619 of ArnA protein are involved in interactions with inhibitors. Thus, this study could be useful to understand the proper binding mode of inhibitors to inhibit the lipid A modification pathway of ArnA protein from plant pathogen Erwinia amylovora.