A facile synthesis of 1-acyl ethylene glycol-2-phosphoryl-cholines

Palmitoyl diol S- and O-phosphoroamidates of some sterols

The hexamethylphosphorus triamide activated by the addition of iodine at the optimum molar ratio 1.05:0.05 was used as a phosphorylating reagent to synthesize 1-palmitoyloxyethyl-2-O-, 1-palmitoyloxypropyl-3-O- and 1-palmitoyloxybutyl-4-O-(N,N-dimethylamido)thiophosphate and -phosphate derivatives of beta-sitosterol, cholesterol and stigmasterol in a one-pot procedure with overall yields of 80-87%. 1-Palmitoyloxypropyl-3-O-(cholesteryl-3-O)-(N,N-dimethylamido++ +) phosphite was used as a model synthon for the preparation of transamidated morpholido-thiophosphate and -phosphate analogues with final yields of 82-86%.

Synthesis of 1-O-acylethane-2-O-amidothionphosphates and their R,S-alpha-tocopherol derivatives as a new model type of phospholipids

The 1-O-acylethane-2-O-bis(N,N-diethylamido)- and 1-O-acylethane-2-O-(R,S-alpha-tocopheryl-6-O-)-(N,N- diethylamido)-thionphosphate derivatives of stearic acid, oleic acid and linoleic acid have been synthesized as new model phospholipid structures.

Synthesis of enzyme-inhibitory phospholipid analogs. III. A facile synthesis of N-acylaminoethylphosphorylcholines

A facile and efficient synthesis of N-aceylaminoethylphosphorylcholines, a series of inhibitory substrate analogs of phospholipase A2, is described. The procedure consists of a three-step sequence including: (1) N-acylation of ethanolamine with fatty acid chloride, followed by (2) phosphorylation of the alcohol function using 2-chloro-2-oxo-1,3,2-dioxaphospholane and (3) nucleophilic ring opening of the cyclic phosphate triester (IV) with anhydrous trimethylamine. The resulting isosteric amide analogs of glycol-lecithins have been isolated in high yields. The synthesis is illustrated by the preparation of the compounds containing palmitoyl, stearoyl and lauroyl fatty acid side-chains. The N-acylaminoethylphosphorylcholines have been shown to function as reversible phospholipase A2 inhibitors. They are likely to become a new series of useful substrate analogs and an attractive replacement for the n-alkylphosphorylcholines commonly used as single-chain-carrying phospholipase inhibitors.

Comparative action of lysophospholipases on acyl-oxyester and acyl-thioester substrates in micellar and membrane-bound form

Phospholipid analogs in which the acyl-oxyester bond is replaced by an acyl-thioester bond represent convenient substrates for sensitive assays of lipolytic enzymes. It has previously been found that such thioester substrates are hydrolyzed at higher rates than their oxyester counterparts. For bovine liver lysophospholipase II the preferential hydrolysis of thioesters appeared to be due to the thioester linkage per se rather than to the formation of preferred interfaces. The preferential hydrolysis of thioesters persisted when thioester and oxyester substrates were presented to the enzyme either as mixed micelles or incorporated in the bilayer of phospholipid vesicles. The transbilayer distribution of thioester and oxyester substrates is sonicated phospholipid vesicles is identical with no apparent indications for transbilayer movement of both substrates.

A comparison of acyl-oxyester and acyl-thioester substrates for some lipolytic enzymes

1. A comparison of 2-hexadecanoylthio-ethane-1-phosphocholine and 3-hexadecanoylthio-propane-1-phosphocholine and their oxyester counterparts as substrates for some lipolytic enzymes was made. 2. The critical micelle concentration and the transition temperature of the synthetic substrates were compared with the values for 1-hexadecanoyl-sn-glycero-3-phosphocholine. 3. All above-mentioned compounds were deacylated by lysophospholipases. Phospholipase A2 hydrolyzed only the acyl- sulfur- and oxygenester bond in 2-hexadecanoyl-ethane-1-phosphocholine. 4. Kinetic parameters, Km and V, for hydrolysis of these substrates were determined. Km values for thioester substrates were 5--10 fold lower than for the corresponding oxyesters. Maximal hydrolysis rates were 2--5 times higher for the thioesters. 5. Hydrolysis of thioesters by phospholipase A2, lipase and lysophospholipase was shown to proceed by an S-acyl cleavage mechanism. 6. Beef liver lysophospholipase II was rapidly and stoichiometrically inactivated by diisopropylfluorophosphate and bis(p-nitrophenyl) phosphate. Inactivation by the latter inhibitor showed burst-like kinetics. 7. Attempts to show burst-kinetics during the pre-steady state hydrolysis of 2-hexadecanoylthio-ethane-1-phosphocholine by lysophospholipase II were negative. These results are interpreted to indicated that a step prior to deacylation of the enzyme is rate-determining.