An approach towards (+)-allokainic acid via diphenylprolinol-catalyzed direct cross-aldol reaction.

This article describes an enantioselective strategy for the synthesis of the kainoid component, (+)-allokainic acid using an organocatalytic approach. A cross-aldol reaction catalyzed by diphenylprolinol yielded a highly functionalized γ-lactam with excellent enantio- and diastereoselectivity, and the resulting hydroxy pyrrolidone was then utilized to synthesize Ganem's intermediate of (+)-allokainic acid. Krapcho decarboxylation and Wittig olefination were pivotal transformations towards the final trans-substituted Ganem's intermediate.

Synthetic access to syn-functionalised chiral hydroxy pyrrolidines and pyrrolidones: Evaluation of α-glucosidase inhibition activity, docking studies and pharmacokinetics prediction.

A new series of syn-functionalised chiral hydroxy pyrrolidines and pyrrolidones containing α,ß-contiguous stereocenters were synthesized via a diphenylprolinol-catalysed asymmetric cross aldol reaction. The synthesized compounds were characterised and evaluated for their α-glucosidase inhibitory potential. The hydroxy pyrrolidine series (9a-9i) was found to be selectively more potent against the α-glucosidase enzyme as compared to the pyrrolidone series (10a-10i). Pyrrolidine 9b was the most efficacious analogue with an IC50 of 48.31 µM. Compounds 9c, 9d, & 9f were also found to be more potent than the standard drugs acarbose, miglitol and deoxynojirimycin. Furthermore, these compounds were investigated by computational studies using the GLIDE docking module of the Schrödinger suite 2021-4 in which 9b and 9c showed more promising results than the standard drugs acarbose, miglitol, and deoxynojirimycin.

P4O10/TfOH mediated domino condensation-cyclization of amines with diacids: a route to indolizidine alkaloids under catalyst- and solvent-free conditions.

A domino condensation-cyclization method is developed to synthesize indolizidine alkaloids using a P4O10/TfOH reagent system without the employment of either a catalyst or solvent. The use of a few aliphatic and aromatic dicarboxylic acids is shown along with various primary amines. This method is suitable for synthesizing pyrrolo[2,1-a]isoquinolines, pyrido[2,1-a]isoquinolines, and isoindolo[1,2-a]isoquinolinones in excellent yields. When phthalic acid is used, a workup with either NaBH4 or a saturated NaHCO3 solution provided 12b-H or 12b-OH isoindolo[1,2-a]isoquinolinones, respectively.

Synthetic access to thiolane-based therapeutics and biological activity studies.

Secondary metabolites isolated from bioactive extracts of natural sources iteratively pioneer the research in drug discovery. Modern medicine is often inspired by bioactive natural products or the bio-functional motifs embedded in them. One of such consequential bio-functional motifs is the thiolane unit. Thiolane-based bioactive organic compounds have manifested a plethora of astonishing biological activities such as anti-viral, anti-cancer, anti-platelet, α-glucosidase inhibition, anti-HIV, immunosuppressive and anti-microbial activities which renders them excellent candidates in drug discovery. Hence, to scale up the accessibility of thiolane-based therapeutics its chemical syntheses is essential and in addition; a sneak peek in its biosynthesis would give a perspective for developing biomimetic syntheses. This review highlights the development of important thiolane-based therapeutics such as (i) Nuphar sesquiterpene thioalkaloids (ii) Thiosugar sulphonium salts from Salacia sp. (iii) Albomycins (iv) Thiolane-based therapeutics from Allium sp. (v) 4'-thionucleosides summarizing various synthetic strategies, biosynthesis and biological activity studies, covering literature till 2021. We anticipate that this review will inspire chemists and biochemists to take up the challenges encountered in the synthesis and development of thiolane-based therapeutics.

α-Glucosidase inhibition activity and in silico study of 2-(benzo[d][1,3]dioxol-5-yl)-4H-chromen-4-one, a synthetic derivative of flavone.

A synthetic flavone derivative 2-(benzo[d][1,3]dioxol-5-yl)-4H-chromen-4-one (BDC) was synthesized by the one pot reaction method and assessed for α-glucosidase inhibitory activity. The BDC demonstrated dose dependent inhibition of α-glucosidase activity. A maximum inhibition (99.3 ±â€¯0.26%) of α-glucosidase was observed at 27.6 µM. The maximum α-glucosidase inhibitory activity depicted by BDC 27.6 µM concentration was 22.4 fold over the maximum inhibition observed with acarbose (97.72 ±â€¯0.59% at 669.57 µM), a standard commercial anti-diabetic drug. In contrast to acarbose that depicted competitive type inhibition, kinetic studies of α-glucosidase inhibition by BDC demonstrated non-competitive inhibition with Km of 0.71 mM-1 and a Vmax of 0.028 mmol/min. In silico studies suggest allosteric interaction of BDC with α-glucosidase at a minimum binding energy (ΔG) of -8.64 kcal/mol and Ki of 465.3 nM, whereas, acarbose interacted at the active site of α-glucosidase with ΔG of -9.23 kcal/mol and Ki of 172 nM. Thus BDC significantly inhibited α-glucosidase in comparison to acarbose. Moreover, BDC has been endorsed for drug likeness by evaluating it as per Lipinski rule of five. Thus, BDC can be a lead compound for the management of type-2 diabetes mellitus.

Quick Identification of Piperidine Alkaloid from Roots of Grewia nervosa and Their Glucosidase Inhibitory Activity.

Grewia nervosa is a herbal plant used in traditional medicine for different purposes. Bioassay-guided chemical fractionation of G. nervosa roots resulted in an identification of two known and one new compound, namely microgrewiapine A, homomicrogrewiapine, and N-methylmicrocosamine, respectively. Their structures were determined using combination of LC/HR-MS, 1 H-NMR, and IR spectral analyses and followed by comparison with those reported in the literature. The problematic separation of these alkaloids on traditional column chromatography (Silica gel, Octadecyl silane, Sephadex) was resolved by using HPLC. Structurally similar compounds from the piperidine family have been characterized by using HR-MS analysis in combination with NMR data of crude samples. The major constituent i.e. N-methylmicrocosamine isolated from the butanol fraction of methanol root extract (MRE) was found to possess the dose dependent α-glucosidase inhibition activity with an IC50 value of 53.40 µm. Furthermore, N-methylmicrocosamine showed maximum α-glucosidase inhibition of 97.48 ± 0.7% at 107.5 µm, which is approximately 1.3 × 103 fold higher than the activity shown by acarbose (97.72% inhibition at 61.95 mm), a standard anti-diabetic drug available commercially. This work also reports the in vitro α-glucosidase inhibitory activity of the major alkaloids isolated from G. nervosa for the first time.

Iodine-Mediated Intramolecular Dehydrogenative Coupling: Synthesis of N-Alkylindolo[3,2-c]- and -[2,3-c]quinoline Iodides.

An I2/TBHP-mediated intramolecular dehydrogenative coupling reaction is developed for the synthesis of a library of medicinally important 5,11-dialkylindolo[3,2-c]quinoline salts and 5,7-dimethylindolo[2,3-c]quinoline salts. The annulation reaction is followed by aromatization to yield tetracycles in good yield. This protocol is also demonstrated for the synthesis of the naturally occurring isocryptolepine in salt form.

Graphite catalyzed solvent free synthesis of dihydropyrimidin-2(1H)-ones/thiones and their antidiabetic activity.

A solvent free three component condensation reaction between an aldehyde, ethyl acetoacetate and urea catalyzed by graphite, a green catalyst is described for the synthesis of dihydropyrimidin-2(1H)-ones. This protocol is scalable and the catalyst is reusable. This method is also applied for the synthesis of dihydropyrimidin-2(1H)-thiones. α-Amylase, a key enzyme in carbohydrate metabolism is generally targeted for management of type 2 diabetes. The therapeutic potential of the dihydropyrimidinones and dihydropyrimidinthiones to inhibit α-amylase activity was evaluated by in vitro assay. Of the synthesized compounds 3,4-dihydropyrimidin-2(1H)-thione (1k) demonstrated highest inhibition of α-amylase activity.

Synthesis of (R)-norbgugaine and its potential as quorum sensing inhibitor against Pseudomonas aeruginosa.

(R)-Bgugaine is a natural pyrrolidine alkaloid from Arisarum vulgare, which shows antifungal and antibacterial activity. In this Letter, we have accomplished the simple synthesis of norbgugaine (demethylated form of natural bgugaine) employing Wittig olefination and cat. hydrogenation as the key steps and its biological studies are reported for the first time. The synthesized norbgugaine was evaluated for inhibition of quorum sensing mediated virulence factors (motility, biofilm formation, pyocyanin pigmentation, rhamnolipid production and LasA protease) in Pseudomonas aeruginosa wherein swarming motility is reduced by 95%, and biofilm formation by 83%.

Recent developments in the synthesis of five- and six-membered heterocycles using molecular iodine.

Heterocyclic scaffolds represent the key structural subunits of many biologically active compounds. Over the last few years iodine-mediated reactions have been extensively studied due to their low cost and eco-friendliness. This Review covers advances in the field of iodine-mediated synthesis of heterocyclic compounds since 2006, especially with an emphasis on mechanisms of ring formation. In this article, syntheses of different heterocycles are classified based on the manipulation of functional groups.

An expeditious I2-catalyzed entry into 6H-indolo[2,3-b]quinoline system of cryptotackieine.

A synthesis of a series of novel 6H-indolo[2,3-b]quinolines with different substituents on the quinoline ring is described. The method involves reaction of indole-3-carboxyaldehyde with aryl amines in the presence of a catalytic amount of iodine in refluxing diphenyl ether to yield indolo[2,3-b]quinolines in one-pot. The present approach provides a new route for the synthesis of polycyclic structures related to an alkaloid cryptotackieine (neocryptolepine).

Total synthesis of (-)- and (+)-tedanalactam.

The first stereoselective route providing access to both enantiomers of tedanalactam, a naturally occurring piperidone, has been developed. The stereogenic centers were generated by the use of Sharpless asymmetric dihydroxylation. Tandem oxidation-Wittig reaction and one-pot deprotection, lactamization, and oxirane ring formation are the other key elements.

Tandem Wittig-ene reaction approach to kainic acid.

The first example of a tandem Wittig-intramolecular ene reaction approach and its application toward the synthesis of kainic acid is reported. The synthetic pathway involves conversion of prenyl bromide into phosphorane 3, followed by one-pot Wittig olefination and an ene reaction with glyoxalic acid to give the cis fused pyrrolidine skeleton of kainic acid.

Convenient and efficient syntheses of 4-hydroxy-2(E)-nonenal and 4-oxo-2(E)-nonenal.

Lipid peroxidation products 4-hydroxy-2(E)-nonenal (HNE) and 4-oxo-2(E)-nonenal (ONE) were conveniently synthesized using Wittig and Horner-Wardsworth-Emmons (HWE) reaction. Wittig or HWE reaction between an easily prepared phosphorane or phosphonate with glyoxal dimethyl acetal gave a protected 4-oxo-2(E)-nonenal. Hydrolysis gave 4-oxo-2(E)-nonenal, whereas reduction followed by hydrolysis gave 4-hydroxy-2(E)-nonenal.