Efficient syntheses, human and yeast farnesyl-protein transferase inhibitory activities of chaetomellic acids and analogues

An overview on natural farnesyltransferase inhibitors for efficient cancer therapy

As one of the world's five terminally ills, tumours can cause important genetic dysfunction. However, some current medicines for tumours usually have strong toxic side effects and are prone to drug resistance. Studies have found that farnesyltransferase inhibitors (FTIs) extracted from natural materials have a good inhibiting ability on tumours with fewer side effects. This article describes several FTIs extracted from natural materials and clarifies the current research progress, which provides a new choice for the treatment of tumours.

Natural Products Attenuating Biosynthesis, Processing, and Activity of Ras Oncoproteins: State of the Art and Future Perspectives

RAS genes encode signaling proteins, which, in mammalian cells, act as molecular switches regulating critical cellular processes as proliferation, growth, differentiation, survival, motility, and metabolism in response to specific stimuli. Deregulation of Ras functions has a high impact on human health: gain-of-function point mutations in RAS genes are found in some developmental disorders and thirty percent of all human cancers, including the deadliest. For this reason, the pathogenic Ras variants represent important clinical targets against which to develop novel, effective, and possibly selective pharmacological inhibitors. Natural products represent a virtually unlimited resource of structurally different compounds from which one could draw on for this purpose, given the improvements in isolation and screening of active molecules from complex sources. After a summary of Ras proteins molecular and regulatory features and Ras-dependent pathways relevant for drug development, we point out the most promising inhibitory approaches, the known druggable sites of wild-type and oncogenic Ras mutants, and describe the known natural compounds capable of attenuating Ras signaling. Finally, we highlight critical issues and perspectives for the future selection of potential Ras inhibitors from natural sources.

Chemical approaches to inhibitors of isoprenoid biosynthesis: targeting farnesyl and geranylgeranyl pyrophosphate synthases

The chemical synthesis of farnesyl and geranylgeranyl pyrophosphate synthase inhibitors are surveyed.

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.

De novo synthesis of (Z)- and (E)-7-hexadecenylitaconic acids by a selective lignin-degrading fungus, Ceriporiopsis subvermispora

Ceriporic acids are a class of alk(en)ylitaconic acids produced by a selective lignin-degrading fungus, Ceriporiopsis subvermispora. Their structural units have similarity with biologically important lichen acids, such as chaetomellic and protolichesterinic acids. The unique function of alkylitaconic acid is the redox silencing of the Fenton reaction system by inhibiting reduction of Fe(3+). As estimated by the catalytic function of Delta9-desaturases, 7-hexadecenyl derivatives bearing a trans configuration have not been reported in the family of alk(en)ylitaconic acids, i.e. the structurally similar lichen acids-alk(en)ylcitraconic and paraconic acids. In this paper, we discuss the isolation of an itaconic acid derivative with an (E)-7-hexadecenyl chain from cultures of C. subvermispora. To identify the natural metabolite, (E)- and (Z)-7-hexadecenylitaconic acids were chemically synthesised. The isolated metabolite was identical to the synthetic (E)-hexadecenylitaconic acid and was designated as ceriporic acid D. Administration of (13)C-[U]-glucose demonstrated that ceriporic acid C and trans-7-hexadecenylitaconic acid (ceriporic acid D) were biosynthesised de novo by C. subvermispora.

Total Synthesis and Biological Evaluation of (−)-Pectinatone Employing a Methyl-Branched Wax Ester as Key Building Block

Unnatural (-)-pectinatone ((-)-3) was prepared in five steps starting from the highly methyl-branched wax ester 4, employing bromination of the ester enolate and subsequent base-induced elimination to the enoate 6 as the key step. Both (-)-3 and the amides 8b and 8c, which were isolated as by-products in the reaction sequence, displayed antimicrobial activity and cytotoxicity.

New fungal metabolite geranylgeranyltransferase inhibitors with antifungal activity

Geranylgeranyltransferase I (GGTase I) catalyzes the post-translational transfer of lyophilic diterpenoid geranylgeranyl to the cysteine residue of proteins terminating with a CaaX motif such as Rho1p and Cdc42p. It has been shown that GGTase I activity is essential for viability of Saccharomyces cerevisiae and hence its inhibition is a potential antifungal target. From natural product screening, a number of azaphilones including one novel analog were isolated as broad-spectrum inhibitors of GGTase I. Isolation, structure elucidation, GGTase I inhibitory activities and antifungal activities of these compounds are described.

Synthesis of mono- and disaccharide analogs of moenomycin and lipid II for inhibition of transglycosylase activity of penicillin-binding protein 1b

Three types of mono- and disaccharides 3a,b, 4a-c, 5, and some chaetomellic acid A analogs 6 and 42-44 were synthesized as potential inhibitors of the transglycosylase activity of penicillin-binding protein 1b (PBP1b), a key bacterial enzyme responsible for the formation of the polysaccharide backbone of peptidoglycan as well as for cross-linking of its peptide portions. The target compounds combine structural features of both the active portion of moenomycin and the natural PBP1b substrate, lipid II. The desired skeletons were obtained in a convergent fashion involving attachment of the lipid-alkylated glyceric acid moieties 11a,b to the corresponding carbohydrate-containing phosphonic acids 23, 24a, and 24b. Compounds 3a,b were prepared to verify the distance requirements between the sugar and the noncleavable C-phosphonate moieties. Compounds 4a-c were synthesized to examine the importance of the first sugar unit of moenomycin, a known inhibitor of transglycosylase catalysis by PBP1b, with respect to antibiotic activity. These were prepared by condensation of 11a,b with 28a and 28c, which were made by glycosylation of 3-bromopropanol with oxazolines 25a,b, and Arbuzov reaction with triethyl or trimethyl phosphite, followed by dealkylation with bromotrimethylsilane. Compound 5 was generated to verify the possibility of using a dicarboxylate group to mimic the diphosphate of lipid II. It was synthesized by coupling of alcohol 31 with alpha-trichloroacetimidate 34. Chaetomellic acid A analogs were prepared by a Michael addition to dimethyl acetylenedicarboxylate. With the exception of 3b, all of the target compounds were found to inhibit PBP1b, albeit with modest potency.

Citrafungins A and B, Two New Fungal Metabolite Inhibitors of GGTase I with Antifungal Activity

[structure: see text] Screening of natural products extracts led to the discovery of citrafungins A and B, two new fungal metabolites of the alkylcitrate family that are inhibitors of GGTase I of various pathogenic fungal species with IC(50) values of 2.5-15 microM. These compounds exhibited antifungal activities with MIC values of 0.40-55 microM. The isolation, structure elucidation, relative and absolute stereochemistry, and biological activities of citrafungins are described.

Ceriporic acid C, a hexadecenylitaconate produced by a lignin-degrading fungus, Ceriporiopsis subvermispora

A lignin-degrading basidiomycete, Ceriporiopsis subvermispora produces a series of alkyl- and alkenylitaconates (ceriporic acids). Previously, two alkylitaconic acids with tetradecyl and hexadecyl side chains were isolated and identified as 1-heptadecene-2,3-dicarboxylic acid (ceriporic acid A) and 1-nonadecene-2,3-dicarboxylic acid (ceriporic acid B). In the present study, one hexadecenylitaconate (ceriporic acid C) was isolated and its chemical structure was analyzed by glycolation and subsequent (1) trimethylsilation, or (2) acetalation with acetone and acetone-d6. Analyses of the isolated metabolite demonstrated that the hexadecenylitaconic acid was (Z)-1,10-nonadecadiene-2,3-dicarboxylic acid. The structure of the side chain in ceriporic acid C was the same as that of hexadecenylcitraconate, chaetomellic acid B. Thus, it was found that ceriporic acids share close structural similarity with alk(en)yl citraconate derivatives, chaetomellic acids and other lichen lactones, protolichesterinic, lichesterinic, and murolic acids.

Chemical synthesis, iron redox interactions and charge transfer complex formation of alkylitaconic acids from Ceriporiopsis subvermispora

In 1999, we first reported that a white rot fungus, Ceriporiopsis subvermispora produced a series of novel alkylitaconic acids (ceriporic acids). In the present paper we synthesized the metabolite, 1-nonadecene-2,3-dicarboxylic acid (ceriporic acid B) by Grignard reaction to analyze chemical properties of the alkylitaconates. Mass spectrometer (MS) and nuclear magnetic resonance (NMR) spectra of the synthetic compound was identical to those of the fungal metabolite isolated. The dicarboxylic acid inhibited autoxidation of Fe(2+) to Fe(3+) as well as reduction of Fe(3+) to Fe(2+) by the strong natural reductants, cysteine, glutathione, and ascorbic acid. The formation of charge transfer complexes (CTCs) between 1-heptadecene-2,3-dicarboxylic acid and oxidized intermediates from phenolic substrates were also observed. Thus, we herein report that the new class of lipid-related metabolites produced by C. subvermispora are potential metabolites participating in the control of iron redox reactions and CTCs formation from oxidized lignin fragments.

A facile synthesis of natural products chaetomellic acid A and 1,7(Z)- nonadecadiene-2,3-dicarboxylic acid

Synthesis of recently isolated bioactive natural products chaetomellic acid A anhydride (1) and a novel 1,7(Z)-nonadecadiene-2,3-dicarboxylic acid (2) have been described. Chemoselective carbon[bond]carbon S(N)2' coupling reactions of appropriate Grignard reagents with dimethyl bromomethylfumarate (7) in diethyl ether in the presence of HMPA at room temperature furnished the corresponding diesters 8 and 15 in 60-62% yields. The formed diesters 8 and 15 on hydrolysis gave respectively the corresponding desired diacids 9 and 2 in quantitative yields. Acetic anhydride induced ring closure of diacids 9 and 2 respectively gave the chaetomellic acid A anhydride (1) and isochaetomellic acid B anhydride (16) with 38-39% overall yields in five steps.