Concise Synthesis of the Terpene Core Structure of Suaveolindole Through a Time-Economic Route

The terpene core structure of suaveolindoles was synthesized through a concise route in a time-economical manner. A scalable synthetic route from pulegone delivered the desired α,β,γ,δ-unsaturated ester in a brief period. By way of Eschenmoser-Claisen rearrangement, carbon side chain moiety at the crowded double-allylic position was introduced stereoselectively.

Studies of Physico-chemical Properties and Cytotoxicity of Fruits of Syzygium jambos L. against HeLa and Vero Cell Lines

Syzygium jambos L. belonging to the family Myrtaceae has a long history of using as a dietary fruit and folklore medicine. Investigation of this fruit was carried out to evaluate the different chemical properties and biological activities. The moisture and ash content of the fruit sample were calculated as 86.88 ± 0.61% and 0.29±0.02%, respectively. Dried powder of the fruit was extracted successively with nhexane, dichloromethane (DCM) and methanol (MeOH). UV-Visible and FT-IR spectral analyses confirmed the presence of unsaturated carboxylic acid in n-hexane, unsaturated ester in DCM and a diketone in MeOH extracts. Cytotoxicity assay of different extracts was carried out against HeLa and Vero cell lines and no extract was found to be cytotoxic. Total phenolic contents of the n-hexane, DCM and MeOH extracts were 15.39 ± 0.24, 31.32 ± 0.25 and 42.19 ± 0.16 mg gallic acid equivalent per gram of dry extract, respectively and total flavonoid content of n-hexane, DCM and MeOH extracts were 6.52 ± 0.18, 15.55 ± 0.16 and 8.36 ± 0.16 mg quercetin equivalent per gram of dry extract, respectively. This study establishes that S. jambos fruit can be a potential source of natural antioxidants. Bangladesh Pharmaceutical Journal 24(2): 111-116, 2021

1,5-Dichloroethanoanthracene Derivatives as Antidepressant Maprotiline Analogues: Synthesis and DFT Computational Calculations

The chlorinated tetracyclic 1,5-dichloro-9,10-dihydro-9,10-ethanoanthracen-12-yl)-N-methylmethanamine 1, a maprotiline analogue, has been synthesized via reduction and Diels–Alder reaction followed by reductive amination of Aldehyde 2. Density Functional Theory calculations were performed to identify the possible isomers of the intermediate compound aldehyde 2, these calculations were in a good agreement with experimental result where aldehyde 2 could exist in three isomers with comparable energies. In addition, the side chain of this aldehyde 2 was extended via Wittig reaction to obtain the unsaturated ester 5 that subjected to selective olefinic catalytic hydrogenation to obtain the corresponding saturated ester 6. 1D-NMR (DEPT) and 2D-NMR (HSQC, DQF-COSY) techniques were recruited for structural elucidation in addition to HRMS.

Brucine Diol-Catalyzed Enantioselective Morita-Baylis-Hillman Reaction in the Presence of Brucine N-Oxide

Brucine diol (BD) catalyzed asymmetric Morita–Baylis–Hillman (MBH) reaction is observed for the first time. Brucine N-oxide (BNO) was found to not have an effective chiral catalyst. Faster reaction rate was obtained using unsaturated ester or aromatic aldehydes in the presence of BNO. 4-Nitrobenzaldehyde and α,β-unsaturated ketone/ester were converted to the MBH adduct in moderate yields (up to 74%) with 70% ee value by this catalytic system. The mechanism of BD catalysis is probably initiated by conjugating the vicinal diol of BD to the carbonyl group of the aromatic aldehyde through hydrogen bonding. The tertiary amine of BD acts as a nucleophile to activate vinyl ketone for coupling with the carbonyl of aldehyde through an intramolecular carbonylated reaction. Finally, the breakdown of the complex caused the formation of the MBH adduct (a benzyl-allyl alcohol). The chirality of the benzyl-allyl alcohol is likely affected by the interaction of the bulky asymmetric plane of BD.

Lignins Isolated via Catalyst-Free Organosolv Pulping from Miscanthus x giganteus, M. sinensis, M. robustus and M. nagara: A Comparative Study

As a low-input crop, Miscanthus offers numerous advantages that, in addition to agricultural applications, permits its exploitation for energy, fuel, and material production. Depending on the Miscanthus genotype, season, and harvest time as well as plant component (leaf versus stem), correlations between structure and properties of the corresponding isolated lignins differ. Here, a comparative study is presented between lignins isolated from M. x giganteus, M. sinensis, M. robustus and M. nagara using a catalyst-free organosolv pulping process. The lignins from different plant constituents are also compared regarding their similarities and differences regarding monolignol ratio and important linkages. Results showed that the plant genotype has the weakest influence on monolignol content and interunit linkages. In contrast, structural differences are more significant among lignins of different harvest time and/or season. Analyses were performed using fast and simple methods such as nuclear magnetic resonance (NMR) spectroscopy. Data was assigned to four different linkages (A: β-O-4 linkage, B: phenylcoumaran, C: resinol, D: β-unsaturated ester). In conclusion, A content is particularly high in leaf-derived lignins at just under 70% and significantly lower in stem and mixture lignins at around 60% and almost 65%. The second most common linkage pattern is D in all isolated lignins, the proportion of which is also strongly dependent on the crop portion. Both stem and mixture lignins, have a relatively high share of approximately 20% or more (maximum is M. sinensis Sin2 with over 30%). In the leaf-derived lignins, the proportions are significantly lower on average. Stem samples should be chosen if the highest possible lignin content is desired, specifically from the M. x giganteus genotype, which revealed lignin contents up to 27%. Due to the better frost resistance and higher stem stability, M. nagara offers some advantages compared to M. x giganteus. Miscanthus crops are shown to be very attractive lignocellulose feedstock (LCF) for second generation biorefineries and lignin generation in Europe.

Lignins Isolated via Catalyst-free Organosolv Pulping from Miscanthus x giganteus, M. sinensis, M. robustus and M. nagara: A Comparative Study

As a low-input crop, Miscanthus offers numerous advantages that, in addition to agricultural applications, permits its exploitation for energy, fuel, and material production. Depending on the Miscanthus genotype, season, and harvest time as well as plant component (leaf versus stem), correlations between structure and properties of the corresponding isolated lignins differ. Here, a comparative study is presented between lignins isolated from M. x giganteus, M. sinensis, M. robustus and M. nagara using a catalyst-free organosolv pulping process. The lignins from different plant constituents are also compared regarding their similarities and differences regarding monolignol ratio and important linkages. Results showed that the plant genotype has the weakest influence on monolignol content and interunit linkages. In contrast, structural differences are more significant among lignins of different harvest time and/or season. Analyses were performed using fast and simple methods such as nuclear magnetic resonance (NMR) spectroscopy. Data was assigned to four different linkages (A: b-O-4 linkage, B: phenylcoumaran, C: resinol, D: b-unsaturated ester). In conclusion, A content is particularly high in leaf-derived lignins at just under 70 % and significantly lower in stem and mixture lignins at around 60 % and almost 65 %. The second most common linkage pattern is D in all isolated lignins, the proportion of which is also strongly dependent on the crop portion. Both stem and mixture lignins, have a relatively high share of approximately 20 % or more (maximum is M. sinensis Sin2 with over 30 %). In the leaf-derived lignins, the proportions are significantly lower on average. Stem samples should be chosen if the highest possible lignin content is desired, specifically from the M. x giganteus genotype, which revealed lignin contents up to 27 %. Due to the better frost resistance and higher stem stability, M. nagara offers some advantages compared to M. x giganteus. Miscanthus crops are shown to be very attractive lignocellulose feedstock (LCF) for second generation biorefineries and lignin generation in Europe.

Borylated methyl cinnamates: Expedited synthesis, characterization, crystallographic analysis and biological activities in glycosidase inhibition and in cancer cells lines.

Three cinnamate derivatives bearing a boronate pinacol ester group para, meta and ortho to the a,b-unsaturated ester group have been synthesized via a solventless, expedited Wittig protocol in the best stereoisomeric ratios yet reported, purified by recrystallization, characterized and analyzed by X-ray crystallography. These are valuable building blocks to biologically active derivatives and are themselves biologically active drug leads, displaying excellent selectivities as glycosidase modulators and for future testing as boron neutron capture therapy (BNCT) agents. In a panel of 15 glycosidases, IC50 values of 351 mM and 374 mM were shown for para 2 against almond b-glucosidase and bovine liver b-galactosidase, respectively. For meta 2 the selectivity profile is improved with only inhibition of bovine liver b-galactosidase with an IC50 of 780 mM. These borylated derivatives also possess the capability to be used as BNCT agents. This occurs via irradiation with slow neutrons, thus granting them a switch-on/switch-off toxicity. This is an important new capability imbued into anticancer drugs, too many of which are too toxic in their therapeutic window. BNCT drugs bearing the organic boron pharmacophore have the potential to fine-tune the timing of toxicity delivery.

Lignins Isolated via Catalyst-free Organosolv Pulping from Miscanthus x giganteus, M. sinensis, M. robustus and M. nagara: A Comparative Study

As a low-input crop, Miscanthus offers numerous advantages that, in addition to agricultural applications, permits its exploitation for energy, fuel, and material production. Depending on the Miscanthus genotype, season, and harvest time as well as plant component (leaf versus stem), correlations between structure and properties of the corresponding isolated lignins differ. Here, a comparative study is presented between lignins isolated from M. x giganteus, M. sinensis, M. robustus and M. nagara using a catalyst-free organosolv pulping process. The lignins from different plant constituents are also compared regarding their similarities and differences regarding monolignol ratio and important linkages. Results showed that the plant genotype has the weakest influence on monolignol content and interunit linkages. In contrast, structural differences are more significant among lignins of different harvest time and/or season. Analyses were performed using fast and simple methods such as nuclear magnetic resonance (NMR) spectroscopy. Data was assigned to four different linkages (A: b-O-4 linkage, B: phenylcoumaran, C: resinol, D: b-unsaturated ester). In conclusion, A content is particularly high in leaf-derived lignins at just under 70 % and significantly lower in stem and mixture lignins at around 60 % and almost 65 %. The second most common linkage pattern is D in all isolated lignins, the proportion of which is also strongly dependent on the crop portion. Both stem and mixture lignins, have a relatively high share of approximately 20 % or more (maximum is M. sinensis Sin2 with over 30 %). In the leaf-derived lignins, the proportions are significantly lower on averageStem samples should be chosen highest possible lignin content is desired, specifically from the M. x giganteus genotype which revealed lignin contents up to 27 %.

Michael Addition of Indoles to Enones Catalyzed by a Cationic Iron Salt

Indoles are one of the most valuable nucleophiles in Michael additions catalyzed by a proper Lewis acid. In this paper, we found that a cationic iron salt is effective to carry out the Michael addition of indoles. β-Mono- and disubstituted enones reacted smoothly with indoles under our conditions. The cationic iron catalyst is very active, and the maximum TON was up to 425. Moreover, cationic iron-catalyzed conditions enabled a chemoselective Michael addition of a substrate possessing both enone and α,β-unsaturated ester moieties.