Diastereoselective Synthesis of N-Methylspiroindolines by Intramolecular Mizoroki-Heck Annulations.

Spiroindolines represent a privileged structure in medicinal chemistry, although stereocontrol around the spirocarbon can be a synthetic challenge. Here we present a palladium(0)-catalyzed intramolecular Mizoroki-Heck annulation reaction from (+)-Vince lactam-derived cyclopentenyl-tethered 2-bromo-N-methylanilines for the formation of N-methylspiroindolines. A series of 14 N-methylspiroindolines were synthesized in 59-81% yield with diastereoselectivity >98%, which was rationalized by density functional theory calculations and confirmed through X-ray crystallography. One spiroindoline was converted to an N- and C-terminal protected rigidified unnatural amino acid, which could be orthogonally deprotected.

Angiotensin II AT2 receptor ligands with phenylthiazole scaffolds.

The syntheses and the AT1R and AT2R binding data of a series of new small molecule ligands are reported. These ligands comprise a phenylthiazole scaffold rather than the biphenyl or phenylthiophene scaffolds found in essentially all of the previously described ligands originating from the nonselective AT1R/AT2R ligand L-162,313 and the AT2R selective agonist C21, the latter now in Phase II/III clinical trials. A phenylthiazole rather than the phenylthiophene scaffold that is present in the AT2R selective agonist C21 and in the AT2R selective antagonist C38 had a deleterious effect on the affinity to AT2R. Nevertheless, a significant improvement could be accomplished by introduction of a small bulky alkyl group in the 2-position of the imidazole ring attached through a methylene group bridge to the phenylthiazole scaffold. Hence, a combination of a 2-tert-butyl or a 2-isopropyl group and a butoxycarbonyl furnished potent AT2R selective ligands. Furthermore, a high affinity ligand derived from L-162,313 and exhibiting a > 35 fold selectivity for AT1R was identified (10). The ligand 21 with the 2-tert-butyl group and âˆ¼ 35 fold selectivity for AT2R, demonstrated high stability in human, rat and mouse liver microsomes and a very attractive profile with regard to the inhibition of common drug-metabolizing CYP enzymes. Thus, very low levels of inhibition of CYP 3A (5%), 2D6 (12%), 2C8 (26%), 2C9 (23%) and 2B6 (24%) were observed with the 2-tert-butyl derivative comprising the methoxycarbonyl sulfonamide function, levels that are significantly lower than those obtained with C21 under the same experimental conditions.

2-Alkyl substituted benzimidazoles as a new class of selective AT2 receptor ligands.

Ligands comprising a benzimidazole rather than the imidazole ring that is common in AT2R ligands e.g. in the AT2R agonist C21, can provide both high affinity and receptor selectivity. In particular, compounds encompassing benzimidazoles, substituted in the 2-position with small bulky groups such as an isopropyl (Ki = 4.0 nM) or a tert-butyl (Ki = 5.3 nM) or alternatively a thiazole heterocycle (Ki = 5.1 nM) demonstrate high affinity and AT2R selectivity. An n-butyl chain, as found in the AT1R selective sartans, makes the ligand less receptor selective. The isobutyl group on the biaryl scaffold present in most AT2R selective ligands reported so far was originally derived from the nonselective potent AT1R/AT2R ligand L-162,313. Notably, in all ligands discussed herein, the isobutyl group was substituted by an n-propyl group and ligands with high affinity to AT2R were provided and in addition the majority of them demonstrate a favorable AT2R/AT1R selectivity. The introduction of fluoro atoms in various positions had no pronounced effect on the affinity data. Ligands with a thiazole or a tert-butyl group attached to the 2-position and with a terminal trifluoromethyl butoxycarbonyl sidechain exhibited a similar stability as C21 in human liver microsomes, while other ligands examined were less stable in the microsome assay.

Anti-inflammatory effect and mechanism of action of ellagic acid-3,3',4-trimethoxy-4'-O-α-L-rhamnopyranoside isolated from Hopea parviflora in lipopolysaccharide-stimulated RAW 264.7 macrophages.

Phytochemical investigation of the stem bark of Hopea parviflora resulted in the isolation of 9 compounds; which includes friedelin (1), friedelin-3ß-ol (2), (-)-ampelopsin A (3), (-)-ɛ-viniferin (4), (-)-hopeaphenol (5), vaticaphenol A (6), 2,4,8-trihydroxyphenanthrene-2-O-glucoside (7), ellagic acid-3,3',4-trimethoxy-4'-O-α-L-rhamnopyranoside (8) and ß-sitosterol-ß-D-glucoside (9). Among them, compounds 1, 2, 6, 7, 8 and 9 are isolated for the first time from this species. Further, we evaluated the anti-inflammatory activity of compounds 4, 5, 6, 7 and 8. In this study, compound 8 inhibited the activity of proinflammatory mediators like NO, TNF-α, IL-6, 5-LOX and COX-2, also promoted the action of anti-inflammatory mediator like IL-10 via inhibition of the NF-κB pathway in LPS-stimulated RAW 264.7 macrophages.

Putative Biomimetic Route to 8-Oxabicyclo[3.2.1]octane Motif from a Humulene Sesquiterpenoid Zerumbone.

An approach to expand the diversity of terpenes to novel polycyclic skeletons with contiguous stereogenic centers is described. An unprecedented 8-oxabicyclo[3.2.1]octane motif was obtained in quantitative yield by photoirradiation of zerumbone in the presence of a catalytic amount of Lewis acid. The vital role of light in the isomerization of double bonds in zerumbone, which ensued cyclization via tertiary carbocation intermediate, emulates a biosynthetic route. Synthetic diversification of the phototransformed product afforded epoxy derivatives with up to seven contiguous stereogenic centers and eight-member ring fused tricyclic motifs. The present work sheds light on the possible role of UV irradiation in the biosynthesis of oxo-bridged tricyclic structures from polyene terpenes.

Chloroform as a CO surrogate: applications and recent developments.

The carbonyl moiety is one of the indispensable sub-units in organic synthesis with significant applications in medicinal as well as materials chemistry. Hence the insertion of a carbonyl group via simple and highly efficient routes has been one of the most challenging tasks for organic chemists. Though the direct utilisation of CO gas in carbonylation is the fundamental procedure for the construction of carbonyl compounds, it has certain drawbacks due to its toxic and explosive nature. As a result, the need for cheap and efficient CO surrogates has gained much attention nowadays by which CO gas can be easily generated in situ or ex situ. In this review we discuss the advantages of chloroform as CO surrogate and have surveyed recent carbonylation reactions where chloroform has been used as CO source.

Screening of Musa balbisiana Colla. seeds for antidiabetic properties and isolation of apiforol, a potential lead, with antidiabetic activity.

BACKGROUND: 'Phytonutrients' have been reported to exert an incredible impact on the healthcare system and offer medical benefits including the prevention or treatment of lifestyle-associated diseases. We chose one of the most common and important plant families, Musaceae, for our present study and explored its antidiabetic potential. RESULTS: Seeds of the edible fruits of Musa balbisiana Colla. were investigated for their antidiabetic potential. After estimating the proximate composition, the seeds were extracted with various solvents and evaluated for antidiabetic potential in terms of the inhibition of digestive enzymes, antiglycation activity and in vitro glucose uptake. The acetone extract demonstrated the highest inhibition of α-amylase and α-glucosidase enzymes with IC50 values of 36.67 ± 0.367 and 100.61 ± 0.707 µg mL-1 , respectively. The extract also exhibited significant glycation inhibition with an IC50 value of 86.48 ± 0.751 µg mL-1 . Furthermore, a major phytochemical, apiforol, was isolated from the acetone extract for the first time, which demonstrated promising α-glucosidase inhibition (IC50  = 48.25 ± 0.255 µmol L-1 ), antiglycation property (IC50  = 114.23 ± 0.567 µmol L-1 ) and enhanced glucose uptake in L6 myoblasts. In molecular docking studies, apiforol efficiently bonded to the active sites of α-glucosidase enzyme 3A4A. CONCLUSIONS: As dietary intervention is one of the effective strategies for addressing diabetes, special attention is always given to natural food bio-actives or agro-products for better human health. The results of our study suggest that Musa balbisiana has significant potential as an ingredient in health food formulations by reducing postprandial hyperglycaemia. © 2018 Society of Chemical Industry.

Chloroform as a carbon monoxide source in palladium-catalyzed synthesis of 2-amidoimidazo[1,2-a]pyridines.

A palladium-catalyzed aminocarbonylation strategy exploiting chloroform as a CO source has been developed for the synthesis of biologically potent 2-amidoimidazopyridine scaffolds. The aminocarbonylation reaction was found to be general with a range of amines and substituted imidazopyridines. Preliminary biological evaluation of cytotoxicity on selected examples provides scope for future investigations.

Lewis Acid Catalyzed Regioselective Hydroheteroarylation of Pentafulvenes.

A diverse approach toward the catalytic regioselective nucleophilic addition of nitrogen heterocycles to Lewis acid activated pentafulvenes has been established. The developed protocol introduces pentafulvenes as nonsymmetrical alkenes for the hydroheteroarylation reaction, providing alkylidenecyclopentenylation at the C-3 position of indoles and the C-2 position of pyrrole.