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In the fused ring system of the title compound, C24H27BrO5, the mean plane and maximum deviations of the central pyran ring are 0.0384 (2) and 0.0733 (2) Å, respectively. The cyclohexenone rings both adopt envelope conformations with the tetra-substituted C atoms as flap atoms, whereas the central pyran ring adopts a flattened boat conformation. The central pyran and phenyl substituent rings are almost perpendicular to each other, making a dihedral angle of 89.71 (2)°. In the crystal, pairs of molecules are linked via O—H...O hydrogen bonds, forming inversion dimers with an R22(20) ring motif. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H...H (50.6%), O...H/H...O (22.9%) and C...H/H...C (11.1%) contacts. Quantum chemical calculations for the frontier molecular orbitals were undertaken to determine the chemical reactivity of the title compound.

In the fused ring system of the title compound, C24H27BrO5, the mean plane and maximum deviations of the central pyran ring are 0.0384 (2) and 0.0733 (2) A °, respectively. The cyclohexenone rings both adopt envelope conformations with the tetra-substituted C atoms as flap atoms, whereas the central pyran ring adopts a flattened boat conformation. The central pyran and phenyl substituent rings are almost perpendicular to each other, making a dihedral angle of 89.71 (2)B. In the crystal, pairs of molecules are linked via O--H...O hydrogen bonds, forming inversion dimers with an R²2(20) ring motif. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H...H (50.6%), O...H/H...O (22.9%) and C...H/H...C (11.1%) contacts. Quantum chemical calculations for the frontier molecular orbitals were undertaken to determine the chemical reactivity of the title compound. [ABSTRACT FROM AUTHOR]

During a synthesis of pyranylidene-substituted malonaldehyde, the main reaction product was a ketoaldehyde that was generated by further ANRORC rearrangement of the formed malonaldehyde in the presence of sodium hydroxide. [ABSTRACT FROM AUTHOR]

Anthocyanins (ACNs) are secondary metabolites found in plants. Due to their impressive biological activities, ACNs have gained significant popularity and extensive application within the food, pharmaceutical, and nutraceutical industries. A derivative of ACNs: pyranoanthocyanins (PACNs) possesses more stable properties and interesting biological activities. However, conventional methods for the production of ACNs, including chemical synthesis and plant extraction, involve organic solvents. Microbial synthesis of ACNs from renewable biomass, such as amino acids or flavonoids, is considered a sustainable and environmentally friendly method for large-scale production of ACNs. Recently, the construction of microbial cell factories (MCFs) for the efficient biosynthesis of ACNs and PACNs has attracted much attention. In this review, we summarize the cases of microbial synthesis of ACNs, and analyze the bottlenecks in reconstructing the metabolic pathways for synthesizing PACNs in microorganisms. Consequently, there is an urgent need to investigate the mechanisms behind the development of MCFs for PACNs synthesis. Such research also holds significant promise for advancing the production of food pigments. Meanwhile, we propose potential solutions to the bottleneck problem based on metabolic engineering and enzyme engineering. Finally, the development prospects of natural food and biotechnology are discussed.

Pyran ring breaking is a key step for cellulose pyrolysis to produce small molecular products. Cellotriose was employed as the model compound of cellulose to explore the mechanism of pyran ring breaking based on Density Functional Theory (DFT). Four kinds of reaction mechanisms were studied: (1) directly breaking mechanism, (2) Retro–Diels–Alder mechanism, (3) C6 OH assisted pinacol ring cleavage mechanism and (4) Retro–Aldol mechanism. The calculated results showed that pyran ring break via Retro–Aldol mechanism (with C3 O formed) was kinetically favored over Retro–Diels–Alder mechanism (with C3 C4 bond formed), followed by C6 OH assisted pinacol ring cleavage mechanism, 2′ + 2′ + 2′ and 2 + 2 + 2 mechanism. Activation energies for both of the two-step mechanisms, Retro–Diels–Alder and Retro–Aldol, varied on the positions of C C bond and C O group formed. The results provided a better understanding on pyran ring breaking mechanism during cellulose pyrolysis. [ABSTRACT FROM AUTHOR]

Synthesis of decahydro-1H-benzo[f]chromene system using intermolecular Diels-Alder reaction has been carried out for the construction of skeleton of terpendole class of terpenoids. [ABSTRACT FROM AUTHOR]

Abstract: A simple and convenient method for the one-pot three-component synthesis of 3-pyranyl indoles has been accomplished by tandem Knoevenagel–Michael reaction of 3-cyanoacetyl indole, various aromatic aldehydes and malononitrile catalyzed by InCl3 in ethanol under reflux conditions. The newly synthesized 3-pyranyl indoles were evaluated for anti-microbial, antioxidant, and anticancer activities. Some of the compounds showed good anticancer activity against MCF-7 breast cancer cell lines on comparison with of standard drug. [ABSTRACT FROM AUTHOR]

Abstract: A simple and efficient method for the one-pot three-component synthesis of new spirooxindoles in room temperature is described. The newly synthesized spirooxindoles were screened for anti-microbial activity and the results are good on comparison with of standard antibacterial compounds. [Copyright &y& Elsevier]

Reaction of procyanidin B3 (catechin‐(4α‐8)‐catechin) at pH 12 and 40°C gave a novel doubly‐linked catechinic acid‐catechin dimer, catechinic acid‐(8β‐8, 9‐ O ‐7)‐catechin, together with catechinic acid and a catechinic acid stereoisomer. The novel dimer had an unexpected β‐interunit linkage, which is contrary to the α‐interflavanoid bond of procyanidin B3, indicating that this compound was formed through the cleavage and recombination of the interflavanoid bond. The nature of the reaction products suggests that cleavage of both the interflavanoid bond and the pyran ring occurred and that the interflavanoid bond cleaved prior to the pyran ring. [ABSTRACT FROM AUTHOR]