Synthesis of carbamyl and ether analogs of phosphatidylcholines

A complete synthesis of 1-O-hexadecyl-2-O-N-(heptadec-8-cis-enyl)carbamyl-sn-glycero-3-Phosphocholine, a novel analog of phosphatidylcholine, has been described. Each step is simple to perform and gives the desired products in high yield. Also, some of the intermediates formed during the synthesis have been efficiently utilized to prepare 1-O-hexadecyl-2-O-oleyl-sn-glycero-3-phosphocholine, 1-O-hexadecyl-2-oleoyl-sn-glycero-3-phosphochloine and 3-O-hexadecyl-2-oeloyl-sn-glycero-1-phosphocholine. These phosphatidylcholine (PC) analogs are useful for studying the possible role of phospholipases in the capture and lyses of liposomes in vivo.     

Synthesis of phosphonate analogs of sphingomyelins and preparation of an affinity sorbent for sphingomyelinase purification

Phosphonate analogues of 2-N-stearoyl- (I) and 2-N-(undec-10-enoyl)-sphingomyelins (II) have been synthesised. Compound (II) was used as a starting product for preparation of a sorbent for sphingomyelinase affinity chromatography. The double bond of the unsaturated undec-10-enoyl moiety of the phosphonate analogue (II) was oxidized, and the modified (II) was coupled to amino-Toyopearl HW-65 to give a sorbent containing 4 mumoles of ligand per milliliter of the swollen resin.     

Synthesis and kinetic analysis of some phosphonate analogs of cyclophostin as inhibitors of human acetylcholinesterase

Two new monocyclic analogs of the natural AChE inhibitor cyclophostin and two exocyclic enol phosphates were synthesized. The potencies and mechanisms of inhibition of the bicyclic and monocyclic enol phosphonates and the exocyclic enol phosphates toward human AChE are examined. One diastereoisomer of the bicyclic phosphonate exhibits an IC₅₀ of 3 μM. Potency is only preserved when the cyclic enol phosphonate is intact and conjugated to an ester. Kinetic analysis indicates both a binding and a slow inactivation step for all active compounds. Mass spectrometric analysis indicates that the active site Ser is indeed phosphorylated by the bicyclic phosphonate.     

Inhibition of chymotrypsin by phosphonate and phosphonamidate peptide analogs

A series of mono-, di-, and tetrapeptide analogs incorporating an activated, tetrahedral phosphorus moiety in place of the scissile carbonyl group have been synthesized and evaluated as inactivators of porcine pancreatic elastase (EC 3.4.21.11) and bovine pancreatic chymotrypsin (EC 3.4.21.1). As previously reported [8.]Biochem. Biophys. Res. Commun.112, 1085–1090), the simple phosphonofluoridate analogs of alanine (6a-F) and phenylalanine (6b-F) are the most rapid inactivators yet reported for these enzymes. More hydrolytically stable derivatives of 5b and 6b were explored for chymotrypsin, and the thiophenyl, thiomethyl, and phenyl esters were shown to be effective inactivators, with the latter being the most stable. This strategy was extended to the tetrapeptide level by the synthesis of the four diastereomers of analog 8. However, each isomer proved to be comparable in its behavior toward chymotrypsin. Potential reasons for this unexpected lack of stereoselectivity were investigated, and it was shown that the phosphorus amide substituent is capable of functioning as a leaving group. In a related dipeptide diester analog, -15, a threefold difference in reactivity between phosphorus diastereomers was seen.     

Synthesis and cytostatical evaluation of cytidine- and adenosine-5′-hexadecylphosphate and their phosphonate analogs

Four phospholipid conjugates containing the non-cytotoxic nucleosides cytidine and adenosine were prepared by condensation reactions, and their cytotoxic activity was tested in vitro against the human immortalized mammary epithelial cell H184 A₁N₄, the human mammary tumor cells MaTu and MCF7 and the B lymphoblast cell line Daudi. The synthesized compounds showed considerable activity towards H184 A₁N₄, MaTu and Daudi cells, but they were not effective against MCF7 cells. The phosphorus moiety—either monophosphate or monophosphonate—does not influence the effectiveness of the phospholipid derivatives in the case of the solid tumor cell lines and H184 A₁N₄. The leukemic Daudi cell line is strongly sensitive towards the different types of ester as well as to the type of the nucleoside component. Adenosine-5′-hexadecylphosphate proved to be the most potent compound among the substances prepared (IC₅₀: 9.0 μmol).     

alpha- and beta-substituted phosphonate analogs of LPA as autotaxin inhibitors

Autotaxin (ATX) is an attractive pharmacological target due to its lysophospholipase D activity which leads to the production of lysophosphatidic acid (LPA). Blockage of ATX produced LPA by small molecules could be a potential anticancer chemotherapy. In our previous study, we have identified the two beta-hydroxy phosphonate analogs of LPA (compounds f17 and f18) as ATX inhibitors. With this work, we investigated alpha- and beta-substituted phosphonate analogs of LPA and evaluated them for ATX inhibitory activity. The stereochemistry of beta-hydroxy phosphonates was also studied.     

Derivatives of phosphonate and vinyl phosphate analogs of D-ribose 5-phosphate

Propanal thiosemicarbazone (1a) showed activity in preventing anaphylactic shock in a mouse test-system; it also had some activity in stunting the growth of Botrytis allii. Hexanal thiosemicarbazone (1b) was active in the Botrytis allii test-system, and citral thiosemicarbazone (2) and citral guanylhydrazone nitrate (3) showed some activity in the same test-system. Heptanal guanylhydrazone nitrate (4) had some antibacterial activity against Staphylococcus aureus, and D-threo-pentosulose bis(thiosemicarbazone) (5) prevented anaphylactic shock in the mouse test-system. D-glycero-Tetrosulose bis(thiosemicarbazone) (6), D-lyxo-hexosulose bis-(guanylhydrazone) nitrate (7), D-galacto-heptosulose bis(thiosemicarbazone) (8), and D-galacto-heptosulose bis(guanylhydrazone) sulfate (9) showed some activity in stunting the growth of Botrytis allii. The copper chelate (10a) of D-arabino-hexosulose bis(thiosemicarbazone), and the copper (11a) and palladium (11b) chelates of 6-deoxy-L-arabino-hexosulose bis(thiosemicarbazone) showed antitumor activity in the KB cell-culture test-system. The palladium chelate 11b also showed some activity in the leukemia p-388 mouse test-system.     

Reactions of phosphonate analogs of pyridoxal phosphate with apo-aspartate aminotransferase

We have investigated reactions of the 5-phosphonoethyl and 5-phosphonoethenyl analogs of pyridoxal 5'-phosphate in the coenzyme site of cytosolic aspartate aminotransferase. Acid dissociation constants and equilibrium constants for hydration and for tautomerization have been evaluated for these compounds. In confirmation of previous results, both compounds are partially active. They bind to apoenzyme well and undergo conversion in the presence of glutamate to amine forms which show induced circular dichroism comparable to that of native enzyme. A normal "external" Schiff base is evidently formed with 2-methylaspartate, but the amounts of quinonoid intermediate formed with erythro-3-hydroxyaspartate are less than those formed with pyridoxal phosphate. The pKa of the imine group of the enzyme reconstituted with the phosphonoethyl analog is more than two units lower than that in the native enzyme. Binding of the dicarboxylates glutarate, 2-oxoglutarate, and succinate shifts the pKa upward. The absorption spectra of the resulting complexes indicate the existence of at least three low pH species. A shift of 2.3 to 2.9 ppm to a lower frequency was observed for the 31P NMR signal upon binding of these dicarboxylates or of 2-methylaspartate. Enzyme containing the analogs crystallizes. Polarized absorption spectra suggest that the coenzyme has an orientation similar to that of pyridoxal phosphate in the native enzyme.     

Identification of novel nucleotide phosphonate analogs with potent anti-HCMV activity

We have recently described the discovery of new leads in the area of anti-HCMV research. Further structure - activity relationship studies have allowed us to identify potent and selective anti-HCMV nucleotide analogs. The synthesis as well as structure - activity relationship studies are described.     

Novel isosteric, isopolar phosphonate analogs of oligonucleotides: preparation and properties

A synthetic approach leading to novel-type modified oligothymidylates containing an isosteric, isopolar, enzyme-stable C3'-O-P-CH(2)-O-C4' phosphonate alternative to phosphodiester internucleotide bond was elaborated. The suitable monomers were prepared from 4'-phosphonomethoxy derivatives of alpha-L-threo and beta-D-erythro-2',5'-dideoxythymidine, which were considered interesting as structurally related to nucleoside 5'-monophosphates. The phosphotriester method was applied to the automated synthesis of both homooligomeric phosphonate 15-mer chains and alternating phosphonate-phosphate constructs. The fully modified homooligomers did not hybridize while homooligomers with alternating sequences containing alpha-L-threo-configured units (but not beta-D-erythro-) showed a significant decrease in T(m) values in comparison with natural dT(15). For a comparative study, phosphodiester 4'-CH(3)-substituted oligothymidylate was synthesized and physical studies (NMR, CD, MDS modeling) were undertaken to shed more light on the changes in conformational behavior arising from the chosen structural alterations.     

Synthesis of lipid II phosphonate analogues

Simple analogues of lipid II were synthesized from 3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-1-thio-β-d-glucopyranose using conjugate addition onto ethylidene bisphosphonate and subsequent Wadsworth–Horner–Emmons reaction with long chain aliphatic aldehydes.     

A new scheme for the synthesis of 5'-nucleotide phosphonate analogs

A convenient and general method is proposed for the synthesis of 5'-nucleotide phosphonate analogs starting from 5-deoxy-1,2-O-isopropylidene-alpha-D-xylo-hexofuranose.     

Phase transitions of alkyl ether analogs of phosphatidylcholine

The phase-transition temperatures of aqueous dispersions of diester, monoether and diether analogs of phosphatidylcholine were determinmed using transparinaric acid as a fluorescent probe. The diether analog of phosphatidylcholine has a higher phase-transition temperature, whilst the monoether analog has a lower phase-transition temperature than their diester counterpart.     

Alkyl lysophosphatidic acid and fluoromethylene phosphonate analogs as metabolically-stabilized agonists for LPA receptors

We describe an efficient method for the synthesis of alkyl lysophosphatidic acid (LPA) analogs as well as alkyl LPA mono- and difluoromethylene phosphonate analogs. Each alkyl LPA analog was evaluated for subtype-specific LPA receptor agonist activity using a cell migration assay for LPA(1) activation in cancer cells and an intracellular calcium mobilization assay for LPA(2) and LPA(3) activation. Alkyl LPAs induced pronounced cell migration activity with equivalent or higher potency than sn-1-oleoyl LPA, while the alkyl LPA fluoromethylene phosphonates proved to be less potent agonists in this assay. However, each alkyl LPA analog activated Ca(2+) release by activation of LPA(2) and LPA(3) receptors. Interestingly, the absolute configuration of the sn-2 hydroxyl group of the alkyl LPA analogs was not recognized by any of the three LPA receptors. The use of alkyl LPA analogs further expands the scope of structure-activity studies, which will better define LPA-LPA receptor interactions.     

Synthesis and biological evaluation of phosphonate analogues of nevirapine

A series of nevirapine-based analogues containing the phosphonate functionality were prepared and evaluated in vitro against HIV RT. The effect of the phosphonate was evaluated against the wild type and Y181C HIV replication. An in vivo PK study was performed on a select analogue.     

2-(Substituted phenyl)amino analogs of 1-methoxyspirobrassinol methyl ether: Synthesis and anticancer activity

New analogs of indole phytoalexin 1-methoxyspirobrassinol methyl ether have been designed by replacement of its 2-methoxy group with 2-(substituted phenyl)amino group. Synthesized by spirocyclization methodology, trans- and cis-diastereoisomers of target compounds were isolated and evaluated as potential anticancer and antimicrobial agents. Their molecular geometries were refined by ab initio minimizations. Pharmacophore modeling and QSAR studies were performed in order to correlate their molecular structure and biological activity.     

Synthesis and cytotoxicity of aurilide analogs

The artificial analogs of aurilide (1), a potent cytotoxic cyclodepsipeptide of marine origin, were synthesized, and the structure–activity relationships were investigated.     

Synthesis of ether glyceroglycolipids

The reaction of 1-O-aklyl-2-O-methylglycerols with acetobromosugars in the presence of mercury(II)cyanide leads to stereochemically uniform peracetylated 1-O-aklyl-2-O-methyl-3-O-β-D-glycosylglycerols after column chromatography. Alkaline hydrolysis of the latter compounds affords 1-O-alkyl-2-O-methyl-3-O-β-D-glycosylglycerols, i.e. ether glyceroglycolipids with potential antineoplastic activity. The sequence of reactions described is also applicable to the preparation of radioactively labeled ether glyceroglycolipids in high yields     

Synthesis of macrolide prostaglandin analogs

Prostaglandin analogs of the E- and F₂α-functional type, which are constrined to conformations in which the side-chains are close in space and specifically aligned in the terminal portions by covalent bonding, have been synthesized. These analogs are 1, (ω-1)-macrolides. The syntheses proceed from aldehyde intermediate I $\text{via}$ the Emmon's condensation with dimethyl n-(dimethyl-t-butyl-silyloxy) 2-oxoalkylphosphonate anions (IIa or b). The macrolide closures were performed using 2,2′-dipyridyl disulfide. For the synthesis of 9-ketoprostaglandin macrolides, a free 9-hydroxy is available for oxidation after macrolide closure, so long as the 9-position is protected as the acetate rather than benzoate. Chiroptical data revealed that the conformations of the macrolide prostaglandins are unchanged (relative to the natural uncosntrained prostaglandins) in the vicinity of the five-membered ring and the allyl alcohol unit by the formation of the macrolide linkage.