New synthetic phosphinate analogues of lecithin

The chemical syntheses of two new, completely nonhydrolyzable phosphinate analogues of lecithin are described. These have the structures ROCH(2)CH(OR)CH(2)CH(2)P(O)(O(-))CH(2)CH(2)N(+)(CH(3))(3) and ROCH(2)CH(OR')CH(2)P(O)(O(-))CH(2)CH(2)CH(2)N(+)(CH(3))(3), where R = C(18)H(37) and R' = C(16)H(33); each is thus isosteric with lecithin on either side of the phosphorus function. The infrared spectra of these compounds undergo unexpected changes under mild acid, base, or adsorptive treatment. These are discussed and compared with related lecithin analogues, including the simple phosphinate C(18)H(37)P(O)(O(-))CH(2)CH(2)N(+)(CH(3))(3), whose synthesis is also reported.

Synthesis of diphytanyl ether analogues of phosphatidic acid and cytidine diphosphate diglyceride

The chemical synthesis of 2,3-di-O-phytanyl-sn-1-glycerophosphate was carried out in two ways: (a) by phosphorylation of 2,3-diphytanyl-sn-glycerol with diphenylphosphoryl chloride in pyridine, followed by catalytic hydrogenolysis of the phenyl groups; and (b) by condensation of 1-iodo-2,3-di-O-phytanyl-sn-glycerol with silver di-p-nitrobenzyl phosphate in anhydrous benzene, followed by catalytic hydrogenolysis of the p-nitrobenzyl groups. The free diether phosphatidic acid obtained was converted to the dipotassium and disodium salts. The diether phosphatidic acid was also converted to the diether analogue of cytidine diphosphate diglyceride by condensation with cytidine monophosphate morpholidate in pyridine. The physical properties of these diether analogues are described, as well as their stabilities towards acid hydrolysis.

The in vivo localization of porphyrins

A series of porphyrins with varying side chains was synthesized and tested in the rat for hard and soft tissue binding and photosensitization. It was found that for combination with either type of tissue there was a requirement for groups capable of ionic or hydrogen bonding at more than one edge of the tetrapyrrole nucleus. Thus binding to keratin, collagen and growing bone occurred with purified haematopophyrin, commercial “haematoporphyrin” and haematoporphyrin “derivative”. Little or no binding with these tissues occurred with deuteroporphyrin, deuteroporphyrin dimethyl ester disulphonic acid, haematoporphyrin dimethylether and unexpectedly, porphyrin c and N,N′-diacetyl porphyrin c. Incorporation of iron into the last two named is thought to account for their apparent lack of binding. In the case of growing bone, the same pattern was apparent with the exception that porphyrin c and N,N′-diacetyl porphyrin c were very strong labels. Combination to bone was with the organic rather than with the inorganic component. All soluble porphyrins tested induced a potential photosensitivity on intraperitoneal injection. Using intravenous colloidal carbon as an indicator of an increase in vascular permeability, the photoresponse following excitation with sunlight, mercury vapour lamp or carbon arc was found to be biphasic, with the delayed response altered by dosage and binding ability of porphyrins, and the amount of light absorbed.

Studies of dialkyl ether phospholipids. I. Chemical synthesis of some model compounds

The syntheses of three 1,2-dialkyl-sn-glycero-3-phosphates and one new 1,2-dialkyl-sn-glycerol are described. 1,2-Dioctadecyl-sn-glycero-3-phosphate was obtained by phosphorylation of 1,2-dioctadecyl-sn-glycerol with diphenylphosphorodichloridate and subsequent catalytic hydrogenolysis. 1,2-Dioctadecyl-sn-glycero-3-(methyl)phosphorylcholine was prepared by phosphorylation of the same dialkyl glycerol with methylphosphorodichloridate and subsequent reaction with choline iodide. 1,2-Dimethyl-sn-glycerol was prepared by treatment of 3-benzyl-sn-glycerol with methyl iodide and KOH followed by hydrogenolysis to remove the protecting group. This compound was then phosphorylated with phenylphosphorodichloridate, the product allowed to react with choline iodide, and the iodide-free product hydrogenated catalytically to yield 1,2-dimethyl-sn-glycero-3-phosphorylcholine which was characterized as the cadmium chloride complex. Some improvements in an established synthesis of 1,2-dioctadecyl-sn-glycerol are described.

Synthesis and metabolism of glycerol-3H triether, a nonabsorbable oil-phase marker for lipid absorption studies

A saturated mixed-chain glycerol triether, 1-hexadecyl-2,3-didodecyl glycerol (1-hexadecoxy-2,3-didodecoxypropane), was synthesized with (3)H at positions 9 and 10 or (14)C at position 1 of the hexadecyl moiety. In acute feeding experiments in rats, less than 0.2% of the triether was absorbed, based on lymph and fecal recoveries. Radioactivity was present exclusively as triether in feces, indicating that it was not degraded by digestive or bacterial enzymes. Chronic feeding experiments in rats confirmed the nonabsorbability of the triether and further indicated that it was nontoxic, did not influence the absorption of dietary fat, and mixed intimately with the fat present in colonic contents and feces. The triether that was absorbed was deposited as triether in adipose tissue, liver, and spleen. When administered intraperitoneally to mice, the triether was stored in the tissues and was not metabolized. When the triether was partitioned between an oil phase of triolein or fatty acid and monoglyceride, and an aqueous micellar phase, the triether remained exclusively in the oil phase. The triether appears to be an ideal nonabsorbable oil-phase marker for use in lipid absorption studies.