General strategy for the synthesis of natural and unnatural dialkylmaleic anhydrides

Spirocyclization and Michael addition of 3-benzylidene succinimides: route to spirocyclopentapyrrolidine-tetraones and benzylidene N-arylpyrrolidine-diones

Reactions of 3-benzylidene succinimides with 2-substituted 2-hydroxy-indane-1,3-diones and unsaturated pyrazolones are carried out under basic conditions to afford spirocyclized derivatives and Michael adducts, respectively, with high regio- and stereo-selectivities. The most notable aspect of the reaction is the ability of highly reactive benzylidene succinimide to act as both an electrophile and a nucleophile causing spirocyclization. The reaction proceeded under mild and metal-free conditions and products were isolated in good to high yields. The current strategy utilizes simple and easily accessible precursors, and provides functionally rich products of medicinal interest with two to four contiguous stereogenic centres and complete regioselectivity with excellent diastereoselectivity.

Three-Dimensional Heterocycles by 5-exo-dig Cyclizations of S-Methyl-N-ynonylsulfoximines

Upon treatment with Cs₂CO₃, S-methyl-N-ynonylsulfoximines undergo 5-exo-dig cyclizations to give three-dimensional heterocycles. The reactions proceed at ambient temperature with a wide range of substrates affording the corresponding products in good to excellent yields.

Palladium-Catalyzed Domino Aminocarbonylation of Alkynols: Direct and Selective Synthesis of Itaconimides

The first direct and selective synthesis of substituted itaconimdes by palladium-catalyzed aminocarbonylation of alkynols is reported. Key to the success of this transformation is the use of a novel catalyst system involving ligand L11 and appropriate reaction conditions. In the protocol here presented, easily available propargylic alcohols react with N-nucleophiles including aryl- and alkylamines as well as aryl hydrazines to provide a broad variety of interesting heterocycles with high catalyst activity and excellent selectivity. The synthetic utility of the protocol is demonstrated in the synthesis of natural product 11 with aminocarbonylation as the key step. Mechanistic studies and control experiments reveal the crucial role of the hydroxyl group in the substrate for the control of selectivity.

Annulation of Enals with Carbamoylpropiolates via NHC-Catalyzed Enolate Pathway: Access to Functionalized Maleimides/Iso-maleimides and Synthesis of Aspergillus FH-X-213

Herein we report the N-heterocyclic carbene (NHC)-catalyzed [3 + 2] annulation of α,β-unsaturated aldehydes with carbamoylpropiolates via an unusual enolate pathway leading to the construction of highly functionalized maleimides or isomaleimides. The electronic effect imposed by the alkyl/aryl group present on the amide nitrogen of carbamoylpropiolates plays a crucial role in the selective formation of these important five-membered heterocyclic building blocks. The developed protocol is mild and tolerates a wide range of substituents on both substrates. The application of this protocol in the synthesis of the antibacterial natural product Aspergillus FH-X-213 has also been demonstrated.

(E)-3-Arylidene-4-diazopyrrolidine-2,5-diones: Preparation and Use in RhII-Catalyzed X–H Insertion Reactions towards Novel, Medicinally Important Michael Acceptors

The use of readily available 1-aryl-3-arylidenepyrrolidine-2,5-diones in high yielding direct diazo-transfer reactions and subsequent involvement of the resulting diazo compounds in RhII-catalyzed O–H, S–H, and N–H insertion reactions delivered 4-substituted 1-aryl-3-arylidenepyrrolidine-2,5-diones of defined regiochemistry and geometrical configuration. These products are intended to be studied as Michael acceptors capable of inhibiting thioredoxin reductase, a promising cancer target.

DBU-catalyzed [3 + 2] cycloaddition and Michael addition reactions of 3-benzylidene succinimides with 3-ylidene oxindoles and chalcones

A metal-free DBU catalyzed protocol has been developed for the regioselective [3 + 2] cycloaddition reactions of 3-benzylidene succinimides with 3-ylidene oxindoles to furnish spirooxindole derivatives. The 3-benzylidene succinimides underwent Michael addition with chalcones to provide benzylidene succinimide-tethered propanones. All the reactions proceeded under mild conditions and the products were isolated by simple filtration and washing with ethanol in good yields. The current methodology utilizes simple precursors and provides functionally-rich succinimides with two to five contiguous stereocenters in excellent diastereoselectivity and with complete regioselectivity.

Aldehyde-mediated bioconjugation via in situ generated ylides

We report a technically simple approach for rapid, high-yielding and site-selective aldehyde-mediated bioconjugation for protein labelling and cellular applications.

Secondary Metabolites from the Endophytic Fungus Xylaria sp. hg1009

A detailed chemical investigation of the secondary metabolites produced by the endophytic fungus Xylaria sp. isolated from the stems of Isodon sculponeatus afforded six new compounds, xylariahgins A-F (1-6), two new natural products (7 and 8), along with two known compounds (9 and 10) (Fig. 1). The structures of all compounds were unambiguously established by analyzing their spectroscopic data or referring to pertinent literature. Compounds 1-8 were tested for their cytotoxic activity against five human tumor cell lines.

One-step Barton decarboxylation by micellar catalysis – application to the synthesis of maleimide derivatives

Maleimides being studied or used in various applications, for the first time, a facile entry to Barton decarboxylation in aqueous media is described to obtain in one step substituted N-phenylmaleimide synthons.

Novel route to chaetomellic acid A and analogues: serendipitous discovery of a more competent FTase inhibitor

A new practical route to chaetomellic acid A (ACA), based on the copper catalysed radical cyclization (RC) of (Z)-3-(2,2-dichloropropanoyl)-2-pentadecylidene-1,3-thiazinane, is described. Remarkably, the process entailed: (i) a one-pot preparation of the intermediate N-α-perchloroacyl-2-(Z)-alkyliden-1,3-thiazinanes starting from N-(3-hydroxypropyl)palmitamide, (ii) a two step smooth transformation of the RC products into ACA and (iii) only one intermediate chromatographic purification step. The method offers a versatile approach to the preparation of ACA analogues, through the synthesis of an intermediate maleic anhydride with a vinylic group at the end of the aliphatic tail, a function that can be transformed through a thiol-ene coupling. Serendipitously, the disodium salt of 2-(9-(butylthio)nonyl)-3-methylmaleic acid, that we prepared as a representative sulfurated ACA analogue, was a more competent FTase inhibitor than ACA. This behaviour was analysed by a molecular docking study.

Virtual ligand screening of the p300/CBP histone acetyltransferase: identification of a selective small molecule inhibitor

The histone acetyltransferase (HAT) p300/CBP is a transcriptional coactivator implicated in many gene regulatory pathways and protein acetylation events. Although p300 inhibitors have been reported, a potent, selective, and readily available active-site-directed small molecule inhibitor is not yet known. Here we use a structure-based, in silico screening approach to identify a commercially available pyrazolone-containing small molecule p300 HAT inhibitor, C646. C646 is a competitive p300 inhibitor with a K(i) of 400 nM and is selective versus other acetyltransferases. Studies on site-directed p300 HAT mutants and synthetic modifications of C646 confirm the importance of predicted interactions in conferring potency. Inhibition of histone acetylation and cell growth by C646 in cells validate its utility as a pharmacologic probe and suggest that p300/CBP HAT is a worthy anticancer target.