Asymmetric Synthesis of the 1-epi Aglycon of the Cripowellins A and B

Cripowellins Pause Plasmodium falciparum Intraerythrocytic Development at the Ring Stage

Cripowellins from Crinum erubescens are known pesticidal and have potent antiplasmodial activity. To gain mechanistic insights to this class of natural products, studies to determine the timing of action of cripowellins within the asexual intraerythrocytic cycle of Plasmodium falciparum were performed and led to the observation that this class of natural products induced reversible cytostasis in the ring stage within the first 24 h of treatment. The transcriptional program necessary for P. falciparum to progress through the asexual intraerythrocytic life cycle is well characterized. Whole transcriptome abundance analysis showed that cripowellin B “pauses” the transcriptional program necessary to progress through the intraerythrocytic life cycle coinciding with the lack of morphological progression of drug treated parasites. In addition, cripowellin B-treated parasites re-enter transcriptional progression after treatment was removed. This study highlights the use of cripowellins as chemical probes to reveal new aspects of cell cycle progression of the asexual ring stage of P. falciparum which could be leveraged for the generation of future antimalarial therapeutics.

Production of benzazepine derivatives via four-component reaction of isatins: study of antioxidant activity

In current research, benzazepine derivative is synthesized via a new process of four-component reaction of isatin or its derivatives, α-haloketones, activated acetylenic compounds, isoquinoline and potassium fluoride/clinoptilolite nanoparticles (KF/CP NPs) in acidic solution of H2O2 in water at room temperature. Also, antioxidation property of some prepared benzazepines is investigated by employing trapping diphenyl-picrylhydrazine (DPPH) radical and ability of ferric reduction experiment. Among investigated compounds, compounds 5c have good results relative to BHT and TBHQ as standard antioxidant. Also, the Gram-positive and Gram-negative bacteria disk diffusion research is used for the confirmation of antimicrobial power of some prepared benzazepines. The achieved outcomes of disk diffusion experiment showed that these compounds avoided the growth of bacteria. Our procedure has a few benefits relative to reported method such as good rate of reaction, product with high efficiency, simple removal of catalyst from mixture of reaction. In the yield of the product, KF/clinoptilolite nanoparticles show a satisfactory recyclable activity.

Experimental and computational study of 6-exo and 7-endo cyclization of aryl radicals followed by tandem S(RN)1 substitution

The reaction of N-allyl-N-(2-halobenzyl)-acetamides and derivatives was investigated in liquid ammonia under irradiation with the nucleophiles Me3Sn(-), Ph2P(-) and O2NCH2(-). Following this procedure, novel substituted 2-acetyl-1,2,3,4-tetrahydroisoquinolines and substituted 2-acetyl-2,3,4,5-tetrahydro-1H-benzo[c]azepines were obtained in good yields. These reactions are proposed to occur through the intermediacy of aryl radicals, which by intramolecular 6-exo or 7-endo attack to a double bond cyclize to give aliphatic radicals, which react along the propagation steps of the S(RN)1 chain cycle to afford the cyclic substituted compounds as main products. The reactions were modeled with DFT methods, which provide a rational understanding that relates the product distribution to the structure of the aliphatic radicals proposed as intermediates and the kinetic of their formation.

Amaryllidaceae and Sceletium alkaloids

A great number of natural products, especially alkaloids, which exhibit a range of biological activities including acetylcholinesterase inhibition and antineoplastic, cardiovascular and immunostimulatory activities, have been isolated from the plants of the Amaryllidaceae family. this review summarizes isolation, biological activity, and synthetic studies of these alkaloids. The primary biosynthetic pathways of each type of alkaloids are also proposed.

Enantio- and Regioselective Heck-Type Reaction of Arylboronic Acids with 2,3-Dihydrofuran

Reported herein is a protocol for the enantioselective Pd(II)-catalyzed Heck-type reaction between arylboronic acids and 2,3-dihydrofuran. The highest chemical and optical yields were obtained when a Pd(OAc)2/(R)-MeO(biphenylphosphine) or a Pd(OAc)2/(R)-(2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) catalyst and a Cu(OAc)2 reoxidant were employed.

Chemical and biological aspects of Narcissus alkaloids

This chapter discusses the chemical and biological aspects of Narcissus alkaloids. Numerous alkaloids have been isolated from Narcissus speciesasaresult of the continuing search for novel alkaloids with pharmacological activity in the Amaryllidaceae family. The alkaloids isolated from this genus, classified in relation to the different skeleton types. The different Narcissus wild species and intersectional hybrids, grouped into subgenera and sections, with their corresponding alkaloids, arranged according to their ring system are listed. The biosynthetic pathways of Narcissus alkaloids includes: (1) enzymatic preparation of the precursors, (2) primary cyclization mechanisms, (3) enzymatic preparation of intermediates, (4) secondary cyclization, diversification, and restructuring. The chapter discusses proton nuclear magnetic resonance (1H NMR), carbon nuclear magnetic resonance (13C NMR), and mass spectrometry (MS) for Narcissus alkaloids. A list of the different Narcissus alkaloids, their spectroscopic properties, and literature with the most recent spectroscopic data is given. Several Narcissus extracts shows the following activities: antiviral, prophage induction, antibacterial, antifungal, antimalarial, insecticidal, cytotoxic, antitumor, antimitotic, antiplatelet, hypotensive, emetic, acetylcholine esterase inhibitory, antifertility, antinociceptive, chronotropic, pheromone, plant growth inhibitor, and allelopathic.