Lorenzo Caggiano

Application of Negishi cross-coupling to the synthesis of the cyclic tripeptides OF4949-III and K-13.

Syntheses of the cyclic tripeptides OF4949-III 1 and K-13 2 are reported, in which the key steps are intermolecular and intramolecular Negishi cross-coupling reactions, respectively. In addition, the synthesis of a protected isomer of K-13 25 is reported. The synthesis of K-13 features a tripeptidic organozinc reagent 11, one of the most highly functionalized such reagents to be described. An O-aryltyrosine derivative 15, prepared by S(N)Ar reaction between Boc-tyrosine and 2-fluorobenzaldehyde, followed by Dakin reaction, iodination, and methylation, is used as a common intermediate for all of the syntheses described. The routes to this class of cyclic tripeptide are among the shortest reported to date and demonstrate the high functional group tolerance of the carbon-zinc bond toward peptide derivatives.

A novel silica catalysed stereoselective cyclic carbamate and carbonate rearrangement

Phenylsulfanyl-containing five- and six-membered lactones, cyclic carbamates and carbonates stereospecifically interconvert in the presence of silica gel via thiiranium ions.

Synthesis and antiproliferative activity of some 3-(pyrid-2-yl)-pyrazolines

The synthesis and antiproliferative activity of eleven 3-(pyrid-2-yl)-pyrazolines in two cancer cell lines are reported. X-ray crystallography was obtained of the lead compound 8i which was screened in the NCI 60 human tumour cell line and displayed sub-micromolar activity. Cell cycle analysis, in vitro tubulin assay and confocal microscopy are also reported and suggest that the lead compound disrupts microtubule formation.

Bi(OTf)3-catalysed prenylation of electron-rich aryl ethers and phenols with isoprene: a direct route to prenylated derivatives

Electron-rich aryl ethers and phenols react with isoprene (2-methylbuta-1,3-diene) in the presence of catalytic Bi(OTf)(3) at 40 °C to afford the corresponding prenylated or 2,2-dimethylchroman products, respectively, in moderate to good yields. This transformation offers a convenient and expedient entry to prenylated derivatives of electron-rich aromatics that often display enhanced biological activities. The methodology has been employed in the efficient synthesis of a biologically active natural product and related compounds.

Design, synthesis and antiproliferative activity of urocanic-chalcone hybrid derivatives

Inspired by biologically active natural products, a hybrid analogue that combines the N-Me urocanic side chain of the sarcodictyin family of compounds with the chalcone motif has been proposed, synthesised and examined for antiproliferative activity in three cancer cell lines and one normal primary cell line. The analogues are all synthesised in one or two steps from commercially available materials and, of the compounds examined, the proposed hybrid analogue displays the most active and selective inhibition of cell proliferation in human colon cancer cell line HT29 (IC50 2.9 μM) and highly metastatic human breast carcinoma MDA-MB-231 (IC50 4.8 μM).

New routes to β-cycloalkylalanine derivatives using serine-derived organozinc reagents

Two distinct routes to beta-cycloalkylalanine derivatives have been developed. The first route employs the reaction of the iodoalanine-derived zinc-copper reagent 2 with cycloalk-1-en-3-yl phosphates, and the second uses the palladium-catalysed coupling of the iodoalanine-derived zinc reagent 1 with cycloalkenyl triflates; in each case, catalytic hydrogenation of the unsaturated product leads to the protected beta-cycloalkylalanine. The latter route allows access to a range of cycloalkyl derivatives, with ring sizes of 5-8. beta-(1-Methyl-1-cyclohexyl)alanine may be prepared using reaction of the zinc-copper reagent 2 with 3-methyl-2-cyclohexenyl chloride, followed by hydrogenation. The corresponding cyclopentyl derivative may be prepared by reaction of the same zinc-copper reagent 2 with diethyl geranylphosphate, followed by ring-closing metathesis and hydrogenation.

The enone motif of (+)-grandifloracin is not essential for 'anti-austerity' antiproliferative activity.

We report the synthesis and biological evaluation of three analogues of the natural product (+)-grandifloracin (+)-1. All three analogues exhibit enhanced antiproliferative activity against PANC-1 and HT-29 cells compared to the natural product. The retention of activity in an analogue lacking the enone functional group, 9, implies this structural element is not an essential part of the (+)-grandifloracin pharmacophore.

Stereoselective synthesis of 2,3-difunctionalised thioesters using nucleophilic epoxidation of 1-arylthio-1-nitroalkenes

Stereoselective nucleophilic epoxidation of protected 3-amino and 3-hydroxy-substituted 1-arylthio-1-nitroalkenes, followed by intramolecular capture involving the amino and hydroxyl protecting groups, has led to the formation of isomeric oxazolidinones 5 and 7, and a cyclic carbonate 11. Together with the oxazolidinone precursor anti-alpha-bromo thioester 15a, the absolute and relative stereochemistry of these compounds has been determined by X-ray crystallography.

Stereoselective substituted pyrrolidine and cyclic ether synthesis by PhS migration

The effect of substitution on heterocycle synthesis by a novel silica gel catalysed decarboxylative ring-closing reaction is shown to be stereospecific and dependent on the nature of the nitrogen substituent.

Design, synthesis and antiproliferative activity of indole analogues of indanocine

The design and synthesis of a novel series of indole-analogues of indanocine is reported, together with their antiproliferative activity in the NCIs panel of cancer cell lines. Indanocine displays potent activity against a wide range of cancer cell lines (mean GI50 < 20 nM), including drug-resistant cancer cell lines, and also inhibits the migration of metastatic cancer cells. A number of the described indole-analogues display a similar activity profile to indanocine, exhibiting potent antiproliferative activities in several cancer cell lines, and offer new leads for further development.