Synthesis and reactivity of (1S)-N-(1-phenylethyl)maleimide towards nucleophiles: an application to preparation of chiral pyrroloisothiochroman and pyrrolobenzo[d]thiepine based on π-cationic cyclization

A C-H functionalization approach to diverse nitrogenous scaffolds through conjugate addition of catalytic allyliron nucleophiles

Cyclopentadienyliron(ii) dicarbonyl complexes capable of coordinating to and enhancing the acidity of a range of unsaturated substrates have emerged as a new class of base-metal derived catalysts for C-H functionalization. In this manuscript, the iron-catalyzed C-H functionalization of allylic C(sp3)-H bonds using nitrogen containing α,β-unsaturated carbonyl compounds as coupling partners is reported. Employing a cationic cyclopentadienyliron dicarbonyl complex, this redox neutral process converts simple alkenes into allylic anion equivalents for 1,4-addition into maleimides, acyclic α,β-unsaturated imides, and vinylogous amides. The judicious pairing of pyridine and alkylamine bases with Lewis acid additives allowed each of these classes of substrates to be successfully employed, allowing for the formation of a diverse collection of cyclic and acyclic nitrogen-containing compounds featuring C-C unsaturation. The resulting Michael adducts can be further transformed into a variety of useful scaffolds such as allylated pyrroles, pyrrolidines, and carbocyclic acids.

Salen/salan metallic complexes as redox labels for electrochemical aptasensors

We provide a new route for the functionalization of electrode supporting aptamers conjugated to a salan chelator useful in biosensor devices.

Molecularly Imprinted Nanocavities Capable of Ligand-Binding Domain and Size/Shape Recognition for Selective Discrimination of Vascular Endothelial Growth Factor Isoforms

Vascular endothelial growth factor 165 (VEGF165) is known to be predominantly expressed in the first stage of vascularization; therefore, the detection of VEGF165 is important in the stage diagnosis of cancers. Molecularly imprinted nanocavities, capable of the selective discrimination of VEGF165 from other VEGF isoforms, were prepared by surface-initiated atom transfer radical polymerization. VEGF165 was immobilized on a gold-coated glass substrate by anchored heparin moieties, where the immobilized heparin was able to capture VEGF165 by binding with the heparin-binding domain (HBD) on VEGF165. Molecular imprinting was conducted on the immobilized VEGF165 by using methacrylic acid (MAA) as a functional monomer to interact with basic amino acids outside of the HBD of VEGF165 by electrostatic interaction. After the removal of VEGF165 from the obtained polymer thin layer (ca. 7 nm), VEGF165-imprinted nanocavities remained, in which the heparin moiety and MAA residues were located in suitable positions for VEGF165 recognition. The molecularly imprinted polymer (MIP) thin layer showed a binding affinity for VEGF165 (dissociation constant: 3.4 nM) that was ten times higher than that of the substrate before polymerization (heparin-immobilized substrate). A much lower binding affinity for VEGF121, which contains no heparin-binding domain, was observed. Moreover, the MIP thin layer distinguished VEGF165 from VEGF189, which possesses a larger molecular size than VEGF165, an amino acid sequence homology of 87%, and contains HBDs, whereas the heparin-immobilized substrate showed almost no selectivity. These results suggested that the heparin moiety within the nanocavity provided HBD selectivity and the polymer matrix composed of the molecularly imprinted nanocavity provided size/shape selectivity, which resulted in the highly selective discrimination of VEGF isoforms.

General and Versatile Entry to 4,5-Fused Polycyclic Imidazolones Systems. Use of the Tandem Transposition/π-Cyclization of N-Acyliminium Species

A simple and efficient methodology for the synthesis of 4,5-fused imidazolidin-2-ones from bicyclic and tricyclic ketones in a four-step sequence was described, by successive spirohydantoin Bucherer-Berg formation, mono- and dialkylation of the nitrogen atom of the hydantoin ring, regioselective reduction of one carbonyl function, and cationic cyclization associated with ring expansion. The key step of this sequential reaction was based on a tandem transposition/intramolecular amidoalkylation of cyclic spiro-N-acyliminium species. The process seems to be easy, general, regiospecific, resulted in the formation of polyheterocyclic systems containing an imidazolidin-2-one nucleus in good to excellent yields (67-99%), and is compatible with a large-scale production (up to 3 g of product 14, for example). Also, this method allows the preparation of the novel heterocycles 14 and 15 that have pharmaceutically interesting profiles, which are not accessible through short current synthetic methods. Finally, products 15 bear a secondary amide function crucial for further transformations, including the introduction of various pharmacophore groups either at the C or the N atoms of the imidazole ring.