Rhodium(II)-Catalyzed Enantioselective Intermolecular Aziridination of Alkenes.

-Symmetrical dirhodium(II) tetracarboxylates are highly efficient catalysts for the asymmetric intermolecular aziridination of substituted alkenes with sulfamates. The reaction proceeds with high levels of efficiency and chemoselectivity to afford aziridines with excellent yields of up to 95% and enantiomeric excesses of up to 99%. The scope of the alkene aziridination includes mono-, di-, and trisubstituted olefins as well as the late-stage functionalization of complex substrates.

Synthesis and Antibacterial Activity of Difluoromethyl Cinnamoyl Amides.

Series of novel amides of isoferulic acid, where the phenolic hydroxyl was replaced by a difluoromethyl group, were synthesized and their in vitro antibacterial activities assayed against fourteen bacterial strains (six Gram-positive and eight Gram-negative). A one-pot methodology was developed to obtain the 3'-(difluoromethyl)-4'-methoxycinnamoyl amides using Deoxofluor as a fluorinating agent. The -isopropyl, -isopentyl, and -(2-phenylethyl) amides , and were the most active and selective against (MIC = 8 µg/mL) with and displaying negligible or no cytotoxicity against HepG2 and A549 cells.

Late-stage C-H amination of abietane diterpenoids.

This study aims at highlighting the synthetic versatility of the rhodium-catalyzed C-H amination reactions using iodine(iii) oxidants for the late-stage functionalization of natural products. Inter- and intramolecular nitrene insertions have been performed from various abietane diterpenoids, leading to the amination of the C-3, C-6, C-7, C-11 and C-15 positions. Ca.

Antitumor effectiveness of a combined therapy with a new cucurbitacin B derivative and paclitaxel on a human lung cancer xenograft model.

Non-small cell lung cancer (NSCLC) is one of the most common malignant tumors, with a high mortality rate due to the elevated risk of resistance. Natural cucurbitacins and their derivatives are recognized as promising antitumor compounds for several types of cancer, including NSCLC. In a recent study published by our research group, DACE (2-deoxy-2-amine-cucurbitacin E), which is a semisynthetic derivative of cucurbitacin B, showed potential in vitro synergistic antiproliferative effects combined with paclitaxel (PTX) in A549 cells.

Cytotoxic effects of natural and semisynthetic cucurbitacins on lung cancer cell line A549.

Cucurbitacins and their derivatives are triterpenoids that are found in various plant families, and are known for their pharmacological and biological activities, including anti-cancer effects. Lung cancer represents a major public health problem, with non-small-cell lung cancer (NSCLC) being the most frequent and aggressive type of lung cancer. The objective of this work was to evaluate four cucurbitacins (CUCs) for their cytotoxic activity, effects on apoptosis induction, cell cycle progression, anti-migratory, and anti-invasive effects on the human NSCLC cell line (A549 cells).

Antioxidant properties in a non-polar environment of difluoromethyl bioisosteres of methyl hydroxycinnamates.

Objectives: Many natural antioxidants have poor pharmacokinetic properties that impair their therapeutic use. For hydroxycinnamic acids (HCAs) and other phenolic antioxidants, their major drawback is their low lipophilicity and a rapid metabolism. The difluoromethyl group may be considered as a 'lipophilic hydroxyl' due to its hydrogen bond donor and acceptor properties; this prompted us to assess it as a bioisosteric replacement of a phenolic hydroxyl for increasing the lipophilicity of HCAs.

Synergistic Antiproliferative Effects of a New Cucurbitacin B Derivative and Chemotherapy Drugs on Lung Cancer Cell Line A549.

Nonsmall cell lung cancer (NSCLC) represents an important cause of mortality worldwide due to its aggressiveness and growing resistance to currently available therapy. Cucurbitacins have emerged as novel potential anticancer agents showing strong antiproliferative effects and can be promising candidates for combined treatments with clinically used anticancer agents. This study investigates the synergistic antiproliferative effects of a new semisynthetic derivative of cucurbitacin B (DACE) with three chemotherapy drugs: cisplatin (CIS), irinotecan (IRI), and paclitaxel (PAC) on A549 cells.

In vitro and in vivo antitumor activity of a novel semisynthetic derivative of cucurbitacin B.

Lung cancer is the most deadly type of cancer in humans, with non-small-cell lung cancer (NSCLC) being the most frequent and aggressive type of lung cancer showing high resistance to radiation and chemotherapy. Despite the outstanding progress made in anti-tumor therapy, discovering effective anti-tumor drugs is still a challenging task. Here we describe a new semisynthetic derivative of cucurbitacin B (DACE) as a potent inhibitor of NSCLC cell proliferation.

Multivariate SAR and QSAR of cucurbitacin derivatives as cytotoxic compounds in a human lung adenocarcinoma cell line.

This article describes structure-activity relationship (SAR/QSAR) studies on the cytotoxic activity in a human lung adenocarcinoma cell line (A549) of 43 cucurbitacin derivatives. Modeling was performed using the methods partial least squares with discriminant analysis (PLS-DA) and PLS. For both studies, the variables were selected using the ordered predictor selection (OPS) algorithm.

Chemical modification produces species-specific changes in cucurbitacin antifeedant effect.

Cucurbitacins are secondary metabolites that mediate insect plant interactions not only as allomones against generalists but also as kairomones for specialist herbivores. This study was undertaken to identify the potential of cucurbitacin derivatives as insect antifeedant agents. The antifeedant capacity against a Cucurbitaceae specialist [ Epilachna paenulata (Coleoptera: Coccinellidae)] and a polyphagous insect [ Pseudaletia adultera (Lepidoptera: Noctuidae)] was evaluated in preference tests in which the insects were given a choice between food plants either treated with the cucurbitacin derivatives or treated with the solvent.

Cytotoxic activity of semi-synthetic derivatives of elatol and isoobtusol.

In the present study, the in vitro cytotoxic effects of six semi-synthetic derivatives of elatol (1) and isoobtusol (2) were investigated. Chemical modifications were performed on the hydroxyl groups aiming to get derivatives of different polarity, namely the hemisuccinate, carbamate and sulfamate. The structural elucidation of the new derivatives was based on detailed NMR and MS spectroscopic analyses.

Synthesis of 6-azaprogesterone and 19-hydroxy-6-azasteroids.

19-Hydroxy-6-azapregnanes were obtained from pregnenolone via a 7-azido-5-oxo-6-nor-5,7-secopregnane intermediate. The 6-azapregnane core was built in good yield in a straightforward way from the secosteroid, by means of a Staudinger (aza-Wittig) reaction. Finally the 19-hydroxy-6-azapregnane was transformed into 19-hydroxy-6-azaprogesterone (that cyclized spontaneously to the 19→3 hemiketal) and 6-azaprogesterone.

Synthesis and cytotoxic activity evaluation of dihydrocucurbitacin B and cucurbitacin B derivatives.

Two cucurbitacins, dihydrocucurbitacin B (1) and cucurbitacin B (2), which can be obtained in large amounts from the roots of Wilbrandia ebracteata and from the fruits of Luffa operculata, respectively, were used as starting materials for the preparation of a library of 29 semi-synthetic derivatives. The structural changes that were performed include the removal, modification or permutation of functional groups in rings A and B as well as in the side chain. All new semisynthetic compounds, as well as 1 and 2, were tested in vitro for their cytotoxic effects on non-small-cell lung cancer cells (A549 cells).

New cytotoxic cucurbitacins from Wilbrandia ebracteata Cogn.

Chemical investigation of the roots of Wilbrandia ebracteata Cogn. (Cucurbitaceae) led to the isolation of two new (1- 2) and four known (3- 6) cucurbitacins. Their structures were elucidated by NMR and MS and compared with related compounds.

Synthesis and GABA(A) receptor activity of 2,19-sulfamoyl analogues of allopregnanolone.

The synthesis of new analogues of allopregnanolone with a bridged sulfamidate ring over the beta-face of ring A has been achieved from easily available precursors, using an intramolecular aziridination strategy. The methodology also allows the synthesis of 3alpha-substituted analogues such as the 3alpha-fluoro derivative. GABA(A) receptor activity of the synthetic analogues was evaluated by assaying their effect on the binding of [(3)H]flunitrazepam and [(3)H]muscimol.

Allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one) derivatives with a polar chain in position 16alpha: synthesis and activity.

The lipophilic nature of allopregnanolone prevents its user-friendly application in human medicine. On inspiration by previously prepared allopregnanolone with a 16alpha-bound tetraethylammonium salt, an attempt was made to produce allopregnanolone analogues with polar groups introduced into position 16alpha with the goal of increasing water solubility, brain accessibility, and potency of neuroactive steroids. The Michael addition to derivatives of pregn-16-en-20-one was the key reaction step.

Synthesis of 6,19-sulfamidate bridged pregnanes.

Conformationally restrained substituted pregnane-20-one derivatives were obtained by an intramolecular nitrene addition onto a C-5/C-6 double bond involving a tethered C-19 sulfamoyl moiety. The resulting aziridine underwent regioselective nucleophilic ring opening at C-5 at room temperature with cyanide, fluoride, and acetate. In the isolated case of acetate, a reversal of regioselectivity was observed at higher temperatures, a result attributed to a rearrangement process involving aziridine ring opening at the C-5 position and subsequent migration of the acetyl moiety to C-6.