Synthesis of enantiomerically pure 1-O-phosphocholine-2-O-acyl-octadecane and 1-O-phosphocholine-2-N-acyl-octadecane

This is the first report on the chemical synthesis of enantiomerically pure R- or S-1-O-phosphocholine-2-O-acyl-octadecanes and R- or S-1-O-phosphocholine-2-N-acyl-octadecanes. From a structural point of view these phospholipids are intermediates between phosphatidylcholine and sphingomyelin. The synthesis of these model compounds is based on R- or S-1.2-O-isopropylidene-glyceraldeyde for chain elongation in a Wittig reaction with pentadecane-triphenylphosphine bromide. The resulting 1.2-O-isopropylidene-octadec-3-en is converted to R- or S-1.2-octadecanediol by catalytic hydrogenation of the double bond and by acidic removal of the isopropylidene protecting group. Tritylation of R- or S-1.2-octadecanediol results in the general intermediates R- or S-1-O-trityl-2-hydroxy-octadecane. These are the key intermediates for the synthesis of the phosphatidylcholine- or sphingomyelin-like end products. R- or S-1-O-phosphocholine-2-O-acyl-octadecane is obtained from the tritylated intermediates via benzylation in position 2, acidic detritylation and conversion of the R- or S-1-hydroxy-2-benzyl-octadecanes to the respective phosphocholines via the phosphoethanolamines. Catalytic hydrogenolysis of the benzyl group results in R- or S-1-O-phosphocholine-2-hydroxy-octadecane, which is converted to the phosphatidylcholine-like end products by acylation. R- or S-1-O-phosphocholine-2-N-acyl-octadecane is obtained from the tritylated intermediate by conversion of the R- or S-2-hydroxy group into the N-phthalimido group, which is achieved by inversion of the configuration using the Mitsunobu reaction with phthalimid. After acidic detritylation, the product is converted to the respective S- or R-1-O-phosphocholine derivative in a similar sequence of reactions. The phthalimido group is converted to the 2-amino group, and acylation results in the sphingomyelin-like end products.

Glycosylation by sugar 1,2-O-(1-cyanobenzylidene) derivatives: influence of glycosyl-donor structure and promoter

3,4,6-Tri-O-acetyl-1,2-O-(1-cyanobenzylidene)-alpha-D-galactopy ranoses with differently substituted aromatic nuclei have been synthesised and used as glycosyl donors in reactions with the acceptors methyl 2,3,4-tri-O-acetyl-6-O-trityl-beta-D-galactopyranoside (11) and methyl 2,4,6-tri-O-acetyl-3-O-trityl-beta-D-galactopyranoside (12). The glycosylation of 11 gave only beta products. The effeciency and stereoselectivity of the glycosylations of 12 depend on the nature of the substituent in the aromatic ring. The stereoselectivity for the formation of 1,2-trans-glycosidic bonds was the highest with the p-methoxy-benzylidene derivative with triphenylmethylium triflate as the promoter.

Chromatographic resolution of chiral intermediates in beta-adrenergic blocker synthesis on chiral stationary phases

The enantiomeric purities of optically active intermediates for beta-adrenergic blocking agents prepared via enzyme-assisted processes can be determined rapidly and with high accuracy using HPLC on commercially available columns with chiral supports [Chiralcel OD, OB; Chiralpak OT(+)]. The dependence of the resolution parameters on the substitution pattern of both hydroxy compounds and their esters is reported.

Synthesis of enantiomerically pure lysophosphatidylinositols and alkylphosphoinositols

A convenient synthesis for enantiomeric pure 1-O-(1'-O-alkyl-sn-glycero-3'-phospho)-D (or L)-myo-inositol, 1-O-(1'-O-acyl-sn-glycero-3'-phospho)-D (or L)-myo-inositol and alkylphospho-1-D (or L)-myo-inositol has been described. Starting from myo-inositol, penta-O-acetyl-myo-inositol was made in five steps. Then enantiomeric purification was done by a diastereomeric salts separation method, and the purity of each enantiomer was spectroscopically measured (19F-NMR). The phosphodiester was made via phosphoramidites. The enantiomeric products (greater than 99% optical purity) of all compounds were easily obtained in large quantities (5-10 g). Synthetic phosphatidylinositol analogues of precisely defined structure and configuration are interesting tools for studying signal transduction mechanism and cell activity modulation.

Synthesis of 1,3-diacylaminopropan-2-ols and corresponding 2-acyl derivatives as amide isosteres of natural lipids

N,N'-diacyl-1,3-diaminopropan-2-ols as amide isosteres of 1,3-diacylglycerols are obtained in 50-79% yields by treatment of 1,3-diaminopropan-2-ol with acid chlorides either in ether or THF in the presence of triethylamine and catalytic amounts of 4-dimethyl-aminopyridine. Subsequent acylation of the secondary alcohol function with a variety of carboxylic acids (e.g. fatty acids, N-protected amino acids, drug compounds) can be effected by various techniques (i.e. acid chlorides, symmetrical anhydrides, isopropenyl chloroformate) with yields ranging from 56% to 76%.