Joseph G. Turcotte

Cytotoxic liponucleotide analogs

Nucleotides of nucleosides or bases having known cytotoxic activity are reacted to form corresponding cytotoxic liponucleotide analogs by phosphorylation of molecular species of phosphatidic acids. The resulting cytotoxic liponucleotide analogs exhibit an enhanced therapeutic index and broader spectrum of antitumor activity as compared to the parent nucleoside or base compounds, apparently due to an improved selective uptake thereof by metabolizing tumor cells, and are thus useful cytotoxic, antiviral and antineoplastic agents.

Chemical synthesis and surface properties of an analog of the pulmonary surfactant dipalmitoyl phosphatidylcholine

Abstract An analog, ( S )-[3-[[2,3-bis(hexadecyloxy)propoxyl]hydroxyphosphinyl]-propyl]trimethylammonium hydroxide, inner salt, hydrate (DPPC-analog), of dipalmitoyl phosphatidylcholine (DPPC) was synthesized. The analog differs from pulmonary DPPC in that it: (1) is a dipalmityl diether rather than a dipalmitoyl diester; (2) has a trimethylammonium propylene phosphono polar head instead of a trimethylammonium ethyleneoxy phosphate head; and (3) has an absolute configuration opposite that of pulmonary DPPC. The dynamic surface pressure-area (π-A) characteristics of the DPPC-analog were determined on a Wilhelmy surface balance and compared with those of DPPC at both 23° C and 37° C. The respreading of both surfactants upon compression past collapse was measured quantitatively by a collapse plateau ratio criterion on successive cycles. The post-collapse respreading ability of the DPPC-analog was found to be significantly better than that of DPPC at both 23°C and 37°C as a function of several surface initial conditions. To complement the dynamic surface pressure-area determinations, differential scanning calorimetry and dilatometry measurements were carried out on DPPC and DPPC-analog water dispersions. The results showed that the liquid-crystalline transition temperature of the DPPC-analog is 45° C, slightly higher than the 41° C found for DPPC. Thus, the superior interfacial respreading found for the DPPC-analog at 23° and 37°C indicates that its bulk phase liquid-crystalline transition temperature is not as directly related to its surface properties as it is in the case of DPPC.

Expedient and High-Yield Synthesis of Alkylphos-Phonyl Bichlorides Under Mild, Neutral Conditions: Reaction of Bis(Trimethylsilyl)Alkyl Phosphonates with Oxalyl Chloride/Dimethylformamide

Abstract Structurally variant bis(trimethylsilyl)alkyl phosphonates were converted in high yields (80–88%, distilled) to the corresponding phosphonyl dichlor-ides upon reaction with (COCl)2/DMF.

High pressure liquid chromatographic separation of molecular species of phosphatidic acid dimethyl esters derived from phosphatidylcholine

A majority of the individual molecular species of phosphatidic acid dimethyl esters derived from multispecies egg yolk and soybean phosphatidylcholines have been separated by reverse-phase high pressure liquid chromatography. Two Partisil-10 ODS columns connected in tandem and the eluents acetonitrile or methanol/water (95∶5) were used for molecular species resolution, based on total fatty acyl carbon number and degree of unsaturation.

Chemical synthesis and surface activity of lung surfactant phospholipid analogs. II. Racemic N-substituted diether phospholipids

A series of racemic 16:0 disaturated N-substituted diether phosphonolipid analogs of glycerophospholipids have been synthesized and purified. Isosteric methylene substitution at three of the four ester sites (carboxyl, phosphate) of conventional glycerophospholipids enhanced the hydrophobicity of analog compounds compared with dipalmitoyl phosphatidylcholine (DPPC), the major glycerophospholipid component of lung surfactant. Further substitutions at the nitrogen headgroup also contributed to hydrophobicity/hydrophilicity characteristics, as well as allowing graded variations in headgroup size among the members of the diether phosphonolipid analog series. Interfacial property studies showed that these compounds had significant differences in surface activity characteristics compared with DPPC, including increased adsorption and respreading facility, plus an enhanced ability to generate low surface tension (< 1 to 4 mN/m) on an oscillating bubble apparatus at 37°C. In addition, pressure-volume mechanical studies in surfactant-deficient excised rat lungs showed that the diether phosphonate analog of DPPC could partially restore pressure-volume characteristics toward normal, both as a pure component and in binary could partially restore pressure-volume characteristics toward normal, both as a pure component and in binary mixtures with palmitoyl-oleoyl phosphatidylglycerol. These findings suggest that selected analog compounds, synthesized with relatively small structural modifications from biologic glycerophospholipids, may have eventual applications as components of synthetic exogenous lung surfactants. Of more immediate importance, analog molecules with defined structural variations are convenient molecular probes for developing structure-surface activity correlates for phospholipid-like surfactants and for investigating the specificity of interactions between glycerophospholipids and other compounds such as proteins.

Preparative-scale high-performance liquid chromatography of omega-3 polyunsaturated fatty acid esters derived from fish oil

Marine triglyceride-derived omega-3 polyunsaturated fatty acid ethyl esters were separated by preparative high-performance liquid chromatography on a 25-microns octadecyl stationary phase using a ternary isocratic mobile phase of acetonitrile-tetrahydrofuran-water (466:233:300, v/v/v). The highest purity first-run fractions obtained were ethyl esters of the major marine polyunsaturates eicosapentaenoic acid (20:5 omega 3, 97.7%) and docosahexaenoic acid (22:6 omega 3, 93.7%), and the minor polyunsaturate octadecatetraenoic acid (18:4 omega 3, 98.1%).

Effect of Oral Administration of ‘Essential’ Phospholipid, β-Glycerophosphate, and Linoleic Acid on Biliary Lipids in Patients with Cholelithiasis

6 patients with radiolucent cholelithiasis underwent randomized successive 3-week trials on each of the following medications: beta-glycerophosphate, linoleic acid, or purified soybean lecithin. Bile-rich duodenal fluid was obtained prior to the study and following each treatment period. Soybean lecithin feeding effected a qualitative change in biliary lecithin with increased fatty acid unsaturation, but no significant improvement in biliary cholesterol saturation or lipid composition changes including a proportionate increase in biliary phospholipids resulted from any treatment program. A 6-month therapeutic trial with soybean lecithin plus cholic acid failed to show a therapeutic response indicative of gallstone dissolution in the 6 patients.

The Separation and the Characterization of Long Chain Fatty Acids and Their Derivatives by Reversed Phase High Performance Liquid Chromatography

The potential for the application of chromatography to the analysis of fatty acids was first realized by A. J. James and A. J. P. Martin in 19521. These two noted scientists successfully separated the iso- and ante-isomers of short chain free fatty acids by gas liquid chromatography (GLC). Even today, 35 years later, the method of choice for characterization of fatty acids is capillary gas chromatography with a mass spectrometer as a detector. However, high performance liquid chromatography (HPLC) is now becoming competitive in the separation of fatty acids, especially on the preparative scale.

Lipid conjugates of antiretroviral agents. II. Disodium palmityl phosphonoformate: anti-HIV activity, physical properties, and interaction with plasma proteins.

Disodium palmityl phosphonoformate, a novel lipid phosphoester of the anti HIV agent phosphonoformate (foscarnet), inhibits HIV replication in H9 cells and syncytia formation in MOLT-3 cells as effectively as foscarnet itself, as shown by dose-response data from assays for expression of p17 and p24 viral antigens and syncytia formation. Protein binding studies indicate that in serum, the derivative exists bound to albumin and the lipoproteins, and would therefore be likely to exhibit improved serum lifetime in vivo.

Isolation and purification of lecithin by preparative high-performance liquid chromatography

Mixed-chain, multispecies, egg yolk-derived lecithin was isolated and purified on a silica column with isocratic elution. A method development column (20 x 0.46 cm I.D.) packed with YMC 15-30 microns, 120 A spherical silica and a mobile phase consisting of 5 mM ammonium acetate in acetonitrile-2-propanol-methanol-water (80:13:5:12) was used to separate the lecithin from other phospholipids. The mobile phase conditions for the method development system was adopted for two types of preparative HPLC systems: a Separations Technology SepTech NovaPrep 5000 system with a 20 x 1.93 cm I.D. column and a ST/800A system with a 20 x 5.00 cm I.D. Annular Expansion (A/E) column. The maximum load was 50 microliters of crude solution (2 mg) for the method development column, 0.90 ml (35 mg) for the 20 x 1.93 cm I.D. column and 6.0 ml (240 mg) for the 20 x 5.00 cm I.D. A/E column. The flow-rates were 2, 35 and 235 ml/min, respectively. The fractions collected from the preparative systems were analyzed for purity by analytical-scale high-performance liquid chromatography and by thin-layer chromatography with selective detection with molybdenum blue for phospholipids and detection of all organic compounds by sulfuric acid. Purity of the recovered lecithin was greater than 99%.