Alessandra Silvani

Grignard addition to imines derived from isatine: a method for the asymmetric synthesis of quaternary 3-aminooxindoles.

Addition of Grignard reagents to chiral imines derived from isatine afforded chiral, optically enriched 3-substituted 3-aminooxindoles in satisfactory yields and diastereoisomeric ratios. A general protocol is described for the addition of alkyl, alkenyl, and aryl Grignard reagents. In one case, the absolute configuration at C3 was determined and the selective N-deprotection was described, enabling further synthetic transformations of the reaction product.

Chemical approaches to targeting drug resistance in cancer stem cells.

Cancer stem cells (CSCs) are a subpopulation of cancer cells with high clonogenic capacity and ability to reform parental tumors upon transplantation. Resistance to therapy has been shown for several types of CSC and, therefore, they have been proposed as the cause of tumor relapse. Consequently, much effort has been made to design molecules that can target CSCs specifically and sensitize them to therapy. In this review, we summarize the mechanisms underlying CSC resistance, the potential biological targets to overcome resistance and the chemical compounds showing activity against different types of CSC. The chemical compounds discussed here have been divided according to their origin: natural, natural-derived and synthetic compounds.

Inhibitors of tubulin polymerization: synthesis and biological evaluation of hybrids of vindoline, anhydrovinblastine and vinorelbine with thiocolchicine, podophyllotoxin and baccatin III.

A series of novel hybrid compounds obtained by the attachment of anhydrovinblastine, vinorelbine, and vindoline to thiocolchicine, podophyllotoxin, and baccatin III are described. Two types of diacyl spacers are introduced. The influence of the hybrid compounds on tubulin polymerization is reported. The results highlight the importance of the length of the spacer. Immunofluorescence microscopy and flow cytometry measurements that compound with the best in vitro activity could disrupt microtubule networks in cell and prevent the formation of the proper spindle apparatus, thereby causing cell cycle arrest in the G2/M phase. The newly synthesized compounds were tested in the human lung cancer cell line A549.

Olefin Metathesis Based Approach to Diversely Functionalized Pyrrolizidines and Indolizidines; Total Synthesis of (+)-Monomorine

New scaffolds for the stereoselective synthesis of diversely functionalized chiral enantiopure indolizidines and pyrrolizidines were synthesized from the cross and ring-closing metathesis reactions of appropriate intermediates, readily available from L-pyroglutamic acid. The versatility of this strategy was demonstrated by the synthesis of an indolizidine-based azasugar analogue and of the natural alkaloid (+)-monomorine.

Synthesis of enantiopure diamine ligands related to sparteine, via scandium triflate-catalyzed imino Diels–Alder reactions

Imino Diels–Alder reactions have been investigated as a new route to sparteine analogues. The first enantioselective synthesis of two diastereoisomeric tricyclic diamines, structurally equivalent to the ABC and BCD rings of the naturally occurring alkaloid, is reported, starting from enantiopure intermediates. The effectiveness of the diamines in the lithiation of N-Boc-pyrrolidine is discussed.

Application of the Pd-catalyzed heteroarylation to the synthesis of 5-(indol-2′-yl)pyridin-2-one and 5-(indol-2′-yl)pyran-2-one

Abstract The synthesis of 5-(indol-2′-yl)pyridin-2-ones and 5-(indol-2′-yl)pyran-2-one by Pd-catalyzed reactions is described. The best results are obtained using 2-indolylstannanes or 2-indolylzinc halides to be coupled with 5-bromopyridin-2-ones or 5-bromopyran-2-one in the presence of Pd(PPh3)4 as catalyst. Other Pd-catalyzed reactions are discussed.

N‐[2‐Methyl‐5‐(triazol‐1‐yl)phenyl]pyrimidin‐2‐amine as a Scaffold for the Synthesis of Inhibitors of Bcr‐Abl

N‐[2‐Methyl‐5‐(triazol‐1‐yl)phenyl]pyrimidin‐2‐amine derivatives were synthesized and evaluated in vitro for their potential use as inhibitors of Bcr‐Abl. The design is based on the bioisosterism between the 1,2,3‐triazole ring and the amide group. The synthesis involves a copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) as the key step, with the exclusive production of anti‐(1,4)‐triazole derivatives. One of the compounds obtained shows general activity similar to that of imatinib; in particular, it was observed to be more effective in decreasing the fundamental function of cdc25A phosphatases in the K‐562 cell line.

New solution free and polymer anchored chiral bispidine-based amino alcohols. Synthesis and screening for the enantioselective addition of diethylzinc to benzaldehyde

Abstract A new approach has been evaluated for the preparation of solution free and polymer supported chiral bicyclic amino alcohols. This strategy involves the use of readily available starting materials and allows chiral ligands characterised by the bispidine core, bearing a stereogenic centre β to one of the nitrogen atoms to be obtained. The first results obtained from the application of these ligands in the asymmetric addition reaction of diethylzinc to benzaldehyde are discussed.

Aspidosperma alkaloids via cyclization of secodine intermediate: Synthesis of (±)-3-oxovincadifformine ethyl ester.

Abstract (±)-3-oxovincadifformine ethyl ester 14 has been synthesized through an intramolecular [4π+2π] cycloaddition of the 3-oxosecodine 13 first prepared in turn from the enamide 10 by dehydrogenation with benzeneseleninic anhydride. An insight into the conversion of 10 into 13 was gained, resulting in the suggestion of a plausible mechanistic pathway.

Asymmetric Ugi 3CR on isatin-derived ketimine: synthesis of chiral 3,3-disubstituted 3-aminooxindole derivatives.

Summary An efficient Ugi three-component reaction of a preformed chiral ketimine derived from isatin with various isonitrile and acid components has been developed. The reactions proceeded smoothly and in a stereocontrolled manner with regard to the new center of the Ugi products due to the stereoinduction of the amine chiral residue. A wide variety of novel chiral 3,3-disubstituted 3-aminooxindoles were obtained, a selection of which were subjected to post-Ugi transformations, paving the way to application as peptidomimetics.