A 'Chiron' approach to novel phytosphingosine mimetics based on a cascade [3,3]-sigmatropic rearrangement.

Straightforward access to enantiomerically pure 3,4-diamino-3,4-dideoxyphytosphingosines, as novel analogues of natural d-ribo-phytosphingosine was accomplished, starting from two available chirons: dimethyl l-tartrate and d-isoascorbic acid. A sequential Overman rearrangement followed by late-stage introduction of the alkyl side chain moiety via olefin cross-metathesis is the cornerstone of this approach. The preliminary evaluation study of the synthesised sphingomimetics, based on their ability to inhibit a proliferation of human cancer cells, showed promising cytotoxicity against Jurkat and HeLa cells for (2R,3R,4S)-2,3,4-triaminooctadecan-1-ol trihydrochloride.

Homospisulosine induced apoptosis in cervical carcinoma cells is associated with phosphorylation of Bcl-2 and up-regulation of p27/Kip1.

Spisulosine (1-deoxysphinganine) is a sphingoid amino alcohol isolated from the sea clams that showed potent antiproliferative activity against a broad spectrum of solid tumors but failed in clinical trials due to neurotoxicity. However, its structural similarity to other bioactive sphingoids, interesting mode of action, and appreciable potency against cancer cells make it a suitable lead for future anticancer drug development. The present study was conducted to elucidate mechanisms of the antiproliferative/cytotoxic effects of newly synthesized spisulosine analog homospisulosine (KP7).

Involvement of Both Extrinsic and Intrinsic Apoptotic Pathways in Tridecylpyrrolidine-Diol Derivative-Induced Apoptosis In Vitro.

Despite the decreasing trend in mortality from colorectal cancer, this disease still remains the third most common cause of death from cancer. In the present study, we investigated the antiproliferative and pro-apoptotic effects of (2,3,4)-2-tridecylpyrrolidine-3,4-diol hydrochloride on colon cancer cells (Caco-2 and HCT116). The antiproliferative effect and IC values were determined by the MTT and BrdU assays.

Divergent access to a novel 3,4-diaminophytosphingosine-like ceramide via sequential Overman rearrangement.

A straightforward approach to a novel phytosphingosine-like ceramide has been accomplished. The cornerstone features of this divergent synthesis are a cascade Overman rearrangement of tris(imidate) to introduce three desired stereogenic centres via sequential chirality transfer and an effective olefin cross-metathesis to install a long side chain. The final unusual phytoceramides were evaluated for their capacity to inhibit the proliferation of cancer cell lines.

Straightforward access to novel cytotoxic phytosphingosine-like aminotriols from l-erythrose chiron.

A divergent approach to a small library of long-chain 6-amino-1,4,5-triols as novel phytosphingosine-type entities, together with their preliminary cytotoxic evaluation, was achieved. Construction of the target compounds addressed two key aspects. First, the installation of a carbon-nitrogen bond via two prototypes of [3,3]-sigmatropic rearrangements and second the introduction of an alkyl side chain unit by using a late stage olefin cross-metathesis process.

Synthesis and in vitro anticancer activity of penaresidin-related stereoisomeric analogues.

A straightforward route to penaresidin-based derivatives with an unsubstituted alkyl side chain was developed. To construct these stereoisomeric azetidene-derived alkaloids, [3,3]-sigmatropic rearrangements followed by late stage olefin cross metathesis and an intramolecular nucleophilic type substitution were involved as the key transformations. The protected d-ribofuranose was chosen as the sole chiral source.

Jaspine B Hydrochloride-induced Apoptosis in HeLa Cells Is Associated With Disrupted Sphingolipid Metabolism and Ceramide Overload.

Background/aim: A series of experiments on HeLa cells were conducted to provide new information concerning the anti-cancer properties of jaspine B hydrochloride (JBH).

Materials And Methods: HeLa cells treated with 0.5 μmol/l JBH for 24, 48, and 72 h underwent flow cytometric analysis of the cell cycle, and measurement of phosphatidylserine externalization, mitochondrial membrane potential (MMP), casp-3 activation, cleavage of PARP, ceramide levels, aSMase activity, and Bcl-2 release.

Synthesis and mannosidase inhibitory profile of a small library of aminocyclitols from shikimic acid-derived scaffolds.

A short synthetic route to a small library of aminocyclitols 14·HCl-19·HCl has been elaborated from the common shikimic acid-derived scaffolds 20 and 21. The developed strategy features three oxidative processes ‒ ozonolysis, dihydroxylation and epoxidation ‒ as the key transformations. The stereochemistry of the newly created stereocentres was confirmed either via crystallographic analysis or by means of NOESY experiments conducted on advanced intermediates.

Synthesis and anticancer profile of novel sphingoid base-like compounds with a quaternary stereocentre.

The synthesis of novel sphingoid base-like compounds with a quaternary stereocentre was achieved in a sequence featuring [3,3]-sigmatropic rearrangements and olefin cross-metathesis transformation as the key reaction steps, which were accompanied by the rational selection of suitable functional group transformations. The stereochemistry of the desired tetra-substituted carbon bearing nitrogen functionality was determined via NOESY experiments of the advanced oxazolidine-2-thiones. Cell viability experiments revealed significant antiproliferative/cytotoxic activity of the target compounds 7, ent-7 and 29 against the Jurkat cell line, with the IC values of 6.

Synthetic analogues of marine cytotoxic jaspine B and its stereoisomers.

Synthetic analogues of the cytotoxic jaspine B and its stereochemical congeners have become an attractive target in the synthetic organic community owing to the search for novel therapeutic candidates with more potent anticancer activity, as cancer is the second leading cause of death worldwide. This review article provides insights into the different approaches and strategies available in the literature for the construction of jaspine B-related compounds.

Synthesis and biological activity of sphingosines with integrated azobenzene switches.

A flexible synthetic approach towards biologically active sphingoid base-like compounds with an integrated azobenzene framework was achieved via installing a chiral amino-alcohol fragment into the azobenzene system by utilizing the Wittig olefination of substituted (E)-triphenyl[4-(phenyldiazenyl)benzyl]phosphonium salts and d-isoascorbic acid derived aldehydes. All the prepared derivatives underwent a series of experiments to probe their photochromic properties, including the reversible E/Z isomerisation, material fatigue and thermal relaxation rate. The targeted E- and Z-isomeric sphingoid analogues were screened in vitro for anticancer activity on a panel of seven human malignant cell lines.

Stereoselective synthesis and antiproliferative activity of the isomeric sphinganine analogues.

A flexible synthetic approach to biologically active sphingoid base-like compounds with a 3-amino-1,2-diol framework was achieved through a [3,3]-sigmatropic rearrangement and late stage olefin cross-metathesis as the key transformations. The stereochemistry of the newly created stereogenic centre was assigned via a single crystal X-ray analysis of the (4S,5R)-5-(hydroxymethyl)-4-vinyloxazolidine-2-thione. In order to rationalise the observed stereoselectivity of the aza-Claisen rearrangement, DFT calculations were carried out.

A stereoselective approach towards a small library of cytotoxic isomeric sphingoid bases.

Two approaches to a small library of cytotoxic dihydrosphingosine analogues are described. [3,3]-Sigmatropic rearrangements along with an OCM reaction were used as the key steps for the construction of the two isodihydrosphingosines ent-6 and 10, whereas the functional group manipulations, including Grubbs' metathesis chemistry, were applied to known isothiocyanate scaffolds 15 and 16 to provide access to the enantiomeric forms of ent-6 and 10 and diastereomeric isophytosphingosines ent-7.HCl and 14.

Synthesis of the cytotoxic phytosphingosines and their isomeric analogues.

A straightforward synthesis of l-lyxo- and l-xylo-phytosphingosine along with their isomeric analogues has been accomplished. The salient features of this approach are the utilization of [3,3]-sigmatropic rearrangements to install a C-N bond and application of a late stage Wittig or OCM reaction to incorporate the hydrophobic chain unit. The final compounds were evaluated regarding their ability to alter both leukaemia and solid tumor cancer cells viability.

The convergent synthesis and anticancer activity of broussonetinines related analogues.

The convergent synthesis of broussonetinines related congeners 3 and 4 with the simple C alkyl side chain and differently configured pyrrolidine skeleton has been achieved. Our approach relied on the [3,3]-sigmatropic rearrangements of chiral allylic substrates derived from d-xylose. Cross metathesis of the common oxazolidinone intermediates 7 and 8 with tridec-1-ene followed by alkylative cyclization completed the construction of both C-alkyl iminosugars.

Total synthesis and the anticancer activity of (+)-spisulosine.

The total synthesis of the anticancer agent (+)-spisulosine has been accomplished. The strategy involved a substrate-controlled aza-Claisen rearrangement to establish the erythro-configured amino-alcohol motif followed by deoxygenation to create a methyl side-chain. Subsequent Wittig olefination then permitted the construction of the carbon backbone of the target molecule.

Total synthesis and antiproliferative/cytotoxic profiling of 2-epi-jaspine B.

A straightforward access to 2-epi-jaspine B (4.HCl) has been developed. Key to the approach was the use of Overman rearrangement for the instalment of a stereocentre bearing a nitrogen atom.

Marine cytotoxic jaspine B and its stereoisomers: biological activity and syntheses.

Conformationally constrained sphingolipids such as anhydrophytosphingosines represented by jaspine B (also known as pachastrissamine) and its stereoisomers have become an attractive and timely target for total synthesis due to their significant biological activity as well as the unique structures. This review article describes the biological activity and chemistry of the natural jaspine B and its seven stereoisomers.

Total synthesis of pachastrissamine together with its 4-epi-congener via [3,3]-sigmatropic rearrangements and antiproliferative/cytotoxic evaluation.

Synthesis of the HCl salts of two anhydrophytosphingosines, jaspine B (1) and its 4-epi-congener 5 from easily available dimethyl l-tartrate and/or l-arabinose, is described. The key transformations are the efficient incorporation of a chiral amino group via [3,3]-sigmatropic rearrangements, a Wittig olefination for the instalment of the carbon backbone and the acid-promoted building-up of a tetrahydrofuran framework. Evaluation for in vitro antiproliferative/cytotoxic activity with a panel of human tumour cell lines using a MTT assay revealed for some compounds of our strategy noteworthy activity.

An efficient synthesis of the polar part of sulfamisterin and its analogs.

An efficient synthesis of the polar part of sulfamisterin and its analogs starting from d-xylose is described. The corresponding allylic thiocyanates and trichloroacetimidates were subjected to aza-Claisen rearrangement that effectively generated a quaternary carbon having an amino group as one of the substituents. Subsequent functional group interconversions afforded the highly functionalized branched aminopolyol 29 that is expected to have the crucial application in the construction of sulfamisterin.

A facile synthesis of D-ribo-C(20)-phytosphingosine and its C2 epimer from D-ribose.

A facile synthetic route to d-ribo-C(20)-phytosphingosine 31 and its C2 epimer 32 is described. The Overman rearrangement of allylic trichloroacetimidates derived from the known ribose derivative 7 has been used as the key step. The subsequent functional group interconversions in rearranged products 14 and 15 followed by Wittig olefination, Pd/C-mediated reduction and the removal of protecting groups successfully constructed the final molecules.

Total synthesis of a protected form of sphingofungin E using the [3,3]-sigmatropic rearrangement of an allylic thiocyanate as the key reaction.

An approach to the stereocontrolled synthesis of the protected form of sphingofungin E (32) starting from the known protected d-glucose derivative 3 is described herein. For the construction of a tetrasubstituted carbon atom that is substituted with nitrogen, the [3,3]-sigmatropic rearrangement of thiocyanate 8 was employed. Subsequent functional group interconversions afforded the highly functionalized fragment, allylic bromide 26.

A novel synthetic approach to C-glycosyl-D- and L-alanines.

C-Glycosyl-(S)- and (R)-alanines 12a and 12b were synthesized from the known beta-C-glycoside 1. The nitrogen function was introduced by aza-Claisen rearrangement of the allylic thiocyanate 7, derived from the corresponding alcohol 6. The absolute configuration of the newly created chiral carbon center (C-3) was assigned by X-ray diffraction analysis of the intermediate 3(S)-isothiocyanato-D-glycero-D-galacto-decose 8a.

Microwave accelerated aza-Claisen rearrangement.

A study of microwave-induced and standard thermal Overman rearrangement of selected allylic trichloroacetimidates 1a-1f, 6-8 to the corresponding acetamides 2a-2f, 9-11 is reported. The microwave-assisted rearrangement of trifluoroacetimidate 13 is also described. Using this methodology, an efficient access to versatile allylic trihaloacetamides building synthons was established.