Synthesis of (4,8,2,3,2')--2' -hydroxyhexadecanoyl-9-methyl-4,8-sphingadiemine, the ceramide portion of the fruiting-inducing cerebroside in a basidiomycete , and its (2,3)-isomer

Amides as bioisosteres of triazole-based geranylgeranyl diphosphate synthase inhibitors

Geranylgeranyl diphosphate synthase (GGDPS) inhibitors are of potential therapeutic interest as a consequence of their activity against the bone marrow cancer multiple myeloma. A series of bisphosphonates linked to an isoprenoid tail through an amide linkage has been prepared and tested for the ability to inhibit GGDPS in enzyme and cell-based assays. The amides were designed as analogues to triazole-based GGDPS inhibitors. Several of the new compounds show GGDPS inhibitory activity in both enzyme and cell assays, with potency dependent on chain length and olefin stereochemistry.

Studies with Guanidinium- and Amidinium-Based Inhibitors Suggest Minimal Stabilization of Allylic Carbocation Intermediates by Dehydrosqualene and Squalene Synthases

Dehydrosqualene and squalene synthases catalyze the redox neutral and the reductive, head-to-head dimerization of farnesyl diphosphate, respectively. In each case, the reaction is thought to proceed via an initial dissociation of farnesyl diphosphate to form an allylic carbocation-pyrophosphate ion pair. This work describes the synthesis and testing of inhibitors in which a guanidinium or amidinium moiety is flanked by a phosphonylphosphinate group and a hydrocarbon tail. These functional groups bear a planar, delocalized, positive charge and therefore should act as excellent mimics of an allylic carbocation. An inhibitor bearing a neutral urea moiety was also prepared as a control. The positively charged inhibitors acted as competitive inhibitors against Staphylococcus aureus dehydrosqualene synthase with K_i values in the low micromolar range. Surprisingly, the neutral urea inhibitor was the most potent of the three. Similar trends were seen with the first half reaction of human squalene synthase. One interpretation of these results is that the active sites of these enzymes do not directly stabilize the allylic carbocation via electrostatic or π-cation interactions. Instead, it is likely that the enzymes use tight binding to the pyrophosphate and lipid moieties to promote catalysis and that electrostatic stabilization of the carbocation is provided by the bound pyrophosphate product. An alternate possibility is that these inhibitors cannot bind to the "ionization FPP-binding site" of the enzyme and only bind to the "nonionizing FPP-binding site". In either case, all reported attempts to generate potent inhibitors with cationic FPP analogues have been unsuccessful to date.

A novel chloro-substituted pentenamide from the fruiting bodies of Amanita virgineoides

One unusual chloro-substituted pentenamide, (3R)-4-chloro-3-hydroxy-4-pentenamide (1), together with 11 known compounds (2-12) were isolated from the fruiting bodies of Amanita virgineoides. The structure of 1 including the absolute configuration was characterized by extensive spectroscopic analyses and quantum calculation. Compound 1 displayed no obvious activity against herpes simplex virus (HSV), human enterovirus 71 (EV71) or coxsackievirus B3 (CVB3).

2-Oxoesters: A Novel Class of Potent and Selective Inhibitors of Cytosolic Group IVA Phospholipase A2

Cytosolic phospholipase A₂ (GIVA cPLA₂) is the only PLA₂ that exhibits a marked preference for hydrolysis of arachidonic acid containing phospholipid substrates releasing free arachidonic acid and lysophospholipids and giving rise to the generation of diverse lipid mediators involved in inflammatory conditions. Thus, the development of potent and selective GIVA cPLA₂ inhibitors is of great importance. We have developed a novel class of such inhibitors based on the 2-oxoester functionality. This functionality in combination with a long aliphatic chain or a chain carrying an appropriate aromatic system, such as the biphenyl system, and a free carboxyl group leads to highly potent and selective GIVA cPLA₂ inhibitors (X_I(50) values 0.00007–0.00008) and docking studies aid in understanding this selectivity. A methyl 2-oxoester, with a short chain carrying a naphthalene ring, was found to preferentially inhibit the other major intracellular PLA₂, the calcium-independent PLA₂. In RAW264.7 macrophages, treatment with the most potent 2-oxoester GIVA cPLA₂ inhibitor resulted in over 50% decrease in KLA-elicited prostaglandin D₂ production. The novel, highly potent and selective GIVA cPLA₂ inhibitors provide excellent tools for the study of the role of the enzyme and could contribute to the development of novel therapeutic agents for the treatment of inflammatory diseases.

Enantioselective Synthesis of the (1S,5R)-Enantiomer of Litseaverticillols A and B

An enantioselective synthesis of the (1S,5R)-enantiomer of litseaverticillols A and B was accomplished in line with our previously reported synthetic pathway for their (1R,5S)-enantiomer. The use of "EtSCeCl2" prepared from EtSLi and CeCl3, instead of previously employed EtSLi itself, for the formation of thiol ester intermediates prevented any undesirable epimerization occurring in the process.

Synthesis of medicinally useful lipidicα-amino acids, 2-amino alcohols and diamines

The lipidicα-amino acids (LAAs) are non-naturalα-amino acids with saturated or unsaturated long aliphatic side chains. LAAs and their derivatives (lipid mimetics) together with the lipidic peptides represent a class of compounds which combine structural features of lipids with those of amino acids and peptides. Racemic LAAs may be prepared by classical methods and resolved by chemical or enzymatic methods. LAA amides and esters with saturated or unsaturated long chain amines and alcohols respectively, as well as lipidic dipeptide derivatives inhibit both pancreatic and human platelet phospholipase A2. Lipophilic peptide derivatives are inhibitors of human neutrophil elastase. LAAs and their oligomers have been used as drug delivery system. A Lipid-Core-Peptide system has been designed and used as a combined adjuvant-carrier-vaccine system. A variety of lipid mimetics such as lipidic 2-amino alcohols, lipidic 1,2- and 1,3-diamines have been prepared based upon LAAs. Some of them are potent inhibitors of phospholipase A2. A general approach to enantioselective synthesis of LAAs and lipid mimetics is based on the oxidative cleavage of 3-amino-1,2-diols obtained by the regioselective opening of enantiomerically enriched long chain 2,3-epoxy alcohols.

Effects of thymoquinone-fatty acid conjugates on cancer cells

4-Acylhydrazones and 6-alkyl derivatives of thymoquinone (TQ) were tested for growth inhibition of human HL-60 leukemia, 518A2 melanoma, KB-V1/Vbl cervix, and MCF-7/Topo breast carcinoma cells. Unsaturated side chains conferred greater activities than equally long saturated chains. The number of C==C bonds was less decisive than chain length. The 6-hencosahexaenyl conjugate 3 e was most active in all resistant tumor cells, with IC(50) (72 h) values as low as 30 nM in MCF-7/Topo cells. The conjugates are likely to operate by mechanisms different from that of TQ. For instance, 3 e induced distinct caspase-independent apoptosis in HL-60 and 518A2 cells concomitant with a loss of mitochondrial membrane potential and a subsequent rise in the levels of reactive oxygen species.

Short and efficient synthesis of (2S,3R,4R,5R) and (2S,3R,4R,5S)-tetrahydroxyazepanes via the Henry reaction

The Henry reaction with the easily available alpha-d-xylo-pentodialdose afforded a diastereomeric mixture of nitroaldoses with the alpha-d-gluco- and beta-l-ido-configuration, respectively, in good yield. When n-BuLi was used as the base, the reaction afforded the alpha-d-gluco-nitroaldose as the only product. The reduction of the nitro group in the alpha-d-gluco- and beta-l-ido-nitroaldoses, removal of the protecting groups and intramolecular reductive cyclo-amination afforded the corresponding (2S,3R,4R,5R) and (2S,3R,4R,5S) tetrahydroxyazepanes.

Transformation of D-glucose into 1D-3-deoxy-3-hydroxymethyl-myo-inositol by stereocontrolled intramolecular Henry reaction

[reaction: see text] An intramolecular Henry cyclization provides a promising new strategy for the transformation of nitroheptofuranoses into deoxyhydroxymethylinositols. This method has allowed a stereospecific transformation of d-glucose into 1D-3-deoxy-3-hydroxymethyl-myo-inositol.

A new indolinepeptide fromPaecilomyces sp. J300

A new indolinepeptide (3) was isolated, together with two known compounds, a cerebroside (1) and an alloxazine (2), from silkworm larvae infected with Paecilomyces sp. J300. On the basis of spectroscopic data, their structures were elucidated as (4E, 8E, 2S, 2'R, 3R)-N-2'-hydroxyhexadecanoyl-1-O-beta-D-glucopyranosyl-9-methyl-4, 8-sphingadienine (1), 7,8-dimethylalloxazine (2) and 3beta,5-dihydroxy-1-N-methyl-indoline-2beta-carbonyl amino-D-alanyl-erythro-beta-hydoxyisoleucinyl-glycine (3).

A glucosylceramide with a novel ceramide and three novel ceramides from the basidiomycete Cortinarius umidicola

A glucosylceramide with novel ceramide and three novel ceramide homologs were isolated from the basidiomycete Cortinarius umidicola and structurally characterized. The ceramide portion of the glucocerebroside consists of a rare (4E,8E)-9-methyl-4,8-sphingadienine sphingoid base. In contrast, the three ceramide homologs, while having the same sphingoid base, contain as FA residues 2-hydroxydocosanoic acid, 2-hydroxytricosanoic acid, and 2-hydroxytetracosanoic acid.

Ceramide constituents from five mushrooms

Five mushrooms, Panellus serotinus, Lyophyllum connatum, Amanita pantherina, Sarcodon aspratus and Lepista nuda, have been investigated chemically. Two new ceramides, (2S,3R,4E,8E)-N-hexadecanoyl-2-amino-9-methyl-4,8-octadecadiene-1,3-diol (1) and (2S,3R,4E,8E,9'Z,12'Z)-N-9',12'-octadecadienoyl-2-amino-9-methyl-4,8-octadecadiene-1,3-diol (2), have been isolated from Panellus serotinus. Compound 2 was also isolated from Lyophyllum connatum. Two new ceramides, (2S,2'R,3R,4E,8E)-N-2'-hydroxypentadecanoyl-2-amino-9-methyl-4,8-octadecadiene-1,3-diol (4) and (2S,2'R,3R,4E,8E)-N-2'-hydroxytetradecanoyl-2-amino-9-methyl-4,8-octadeca-diene-1,3-diol (5), have been isolated from Amanita pantherina with (2S,2'R,3R,4E,8E)-N-2'-hydroxyhexadecanoyl-2-amino-9-methyl-4,8-octadecadiene-1,3-diol (3), a known synthetic compound. Compounds 3 and 4 were also isolated from Sarcodon aspratus and compound 3 was isolated from Lepista nuda. The structures of the new compounds were elucidated on the basis of their spectral data.

Synthesis of optically active lipidic alpha-amino acids and lipidic 2-amino alcohols

Lipidic alpha-amino acids (LAAs) are a class of compounds combining structural features of amino acids with those of fatty acids. They are non-natural alpha-amino acids with saturated or unsaturated long aliphatic side chains. Synthetic approaches to optically active LAAs and lipidic 2-amino alcohols (LAALs) are summarized in this review. A general approach to enantioselective synthesis of saturated LAAs is based on the oxidative cleavage of 3-amino-1,2-diols obtained by the regioselective opening of enantiomerically enriched long chain 2,3-epoxy alcohols. Unsaturated LAAs are prepared in their enantiomeric forms by Wittig reaction via methyl (S)-2-di-tert-butoxycarbonylamino-5-oxo-pentanoate. This key intermediate aldehyde is obtained by selective reduction of dimethyl N,N-di-Boc glutamate with DIBAL. (R) or (S) LAALs may be prepared starting from D-mannitol or L-serine. LAAs are converted into LAALs by chemoselective reduction of their fluorides using sodium borohydride with retention of optical purity. Replacement of the hydroxyl group of LAALs by the azido group, followed by selective reduction leads to unsaturated optically active lipidic 1,2-diamines.

Competitive inhibition of lipolytic enzymes. XI. Estimation of the interfacial dissociation constants of porcine pancreatic phospholipase A2 for substrate and inhibitor in the absence of detergents

Based on the strong inhibitory properties of (R)-2-decanoylamino-octanol-1-phosphocholine and its phosphoglycol analogue for porcine pancreatic phospholipase A2, the corresponding 2-decanoyloxy derivatives have been synthesised in both enantiomeric forms and their substrate properties for the enzyme were analysed. The high aqueous solubility in the absence of detergents, combined with low critical micelle concentrations of both the amide- and ester phospholipids allowed the estimation of the interfacial dissociation constants of the enzyme-substrate and enzyme-inhibitor complexes by kinetic and direct binding techniques.

Competitive inhibition of lipolytic enzymes. X. Further delineation of the active site of pancreatic phospholipases A2 from pig, ox and horse by comparing the inhibitory power of a number of (R)-2-acylamino phospholipid analogues

Two series of (R)-phospholipid analogues, each containing a n-propyl group at the C-1 position and various acylamino functions at the C-2 position have been synthesized and their inhibitory properties towards three mammalian pancreatic phospholipases A2 have been determined. The members of the first series of analogues all contained the zwitter-ionic phosphocholine headgroup which in the second series was replaced by the anionic phosphoglycol function. In the saturated 2-acylamino phospholipids the length of the acyl chain ranged from 8 to 18 carbon atoms. The unsaturated 2-acylamino analogues possessed a chain length of 11 or 18 carbon atoms and contained one, two, three or four double bonds. For inhibitors with a saturated acylamino group, the phospholipases A2 from pig, ox and horse show a sharp optimum in inhibitory power Z for an acyl chain length of 10 carbon atoms. The inhibitory behaviour of the unsaturated acylamino analogues is more complex: both the zwitter-ionic and the anionic inhibitors demonstrate an increase in Z with an increasing number of cis-double bonds but the degree of improvement is dependent on the position of the double bonds. Subsequently the influence of polar groups at carbon position 12 of the dodecanoylamino phospholipids on Z was analyzed. Substitution of the terminal methyl group by an OH-function lowers the inhibitory potency of the three enzymes by a factor of 4 to 5 both in the phosphocholine and phosphoglycol series. Replacement of the methyl group by potentially charged functions (-NH2, -COOH) resulted in a complete loss of inhibitory properties. Blocking of the amino group and carboxyl function by t-butyloxycarbonylation and esterification, respectively, fully restored the inhibitory power. Finally we investigated how changes in the polar headgroup and the presence of aromatic rings at the C-1 or C-2 position influenced the inhibitory potency of the analogues.

Conformational studies of amphipathic alpha-helical peptides containing an amino acid with a long alkyl chain and their anchoring to lipid bilayer liposomes

In order to investigate the conformation and orientation of lipid-bound peptides and proteins in the lipid bilayer, basic amphipathic alpha-helical peptides with a long alkyl chain, palmitoyl-(Leu-Ala-Arg-Leu)3-NHCH3 (P-4(3)) and Ac-Leu-Ala-Arg-Leu-Trp-Amy-Arg-Leu-Leu-Ala-Arg-Leu-NHCH3 (Amy-4(3), Amy; alpha-aminomyristic acid) were designed and synthesized. The conformational features and spectroscopic behavior in a buffer solution and in neutral and acidic liposomes were studied by CD, dye-leakage, and fluorescence measurements. The CD data indicated that P-4(3) took an alpha-helical structure in aqueous solution and in neutral and acidic liposomes. On the other hand, Amy-4(3) took a beta-structure in aqueous solution and an alpha-helical structure in neutral and acidic liposomes. The conformational change of Amy-4(3) was confirmed by fluorescence study on lipid titration of the peptide. The dye-leakage experiment showed that both peptides interacted with acidic liposomes to perturb them, but less effectively than Ac-(Leu-Ala-Arg-Leu)3-NHCH3 (4(3)) which has no long alkyl group. Based on these results, a discussion is made concerning the conformation and orientation of peptides in aqueous solution and in the lipid bilayer.