Hydroxytetradecanoic acid, fatty

Total fatty acids were liberated by subjecting Salmonella minnesota Re lipopolysaccharide (or free lipid A) to acidic (4 N HC1, 5 h, 100°C) followed by alkaline (1 N NaOH, 1 h, 100°C) hydrolysis. After extraction (chloroform), the free fatty acids were converted into their methyl esters (diazomethane) and analysed by combined gas-liquid chromatography/mass spectrometry. Alternatively, the fatty acids of lipid A are transesterified by treatment of lipopolysaccharide with methanolic HC1 (2 N HC1 in water-free CHaOH, 18 h, 85°C). By these procedures the following fatty acids were identified (in approximate amounts relative to 2 moles glucosamine) dodecanoic (12 0, 1.1 mole), tetradecanoic (14 0, 0.8 mole), hexadecanoic (16 0, 0.9 mole), 2-hydroxytetradecanoic (2-OH-l4 0, 0.1 mole), and 3-hydroxytetradecanoic acid (3-OH-14 0, 4 moles). In total, therefore, approximately 7 moles of fatty acids are present per mole of lipid A backbone. The stereochemistry of the hydroxylated fatty acids was determined by gas-liquid chromatography of their diastereomeric methoxyacyl-L-phenylethylamide derivatives (24). It was found that 2-hydroxyte-tradecanoic acid possesses the-Ts), and the predominating 3-hydroxytetradecanoic acid the (R) configuration. 

Therefore, of the 2 moles of ester-bound 3-OH-14 0 one is 3-0-acylated by tetradecanoic acid the other should carry a free 3-hydroxyl group. This latter assumption was proven to be correct by the following experiment. Lipid A was treated with t-butyldimethylsilylchloride, ester-bound fatty acids were trans-esterified by NaOCH3 and analysed by gas-liquid chromatography. Besides the other expected fatty acid methyl esters (12 0, 16 0, 3-OCH3-14 0) approximately 1 mole (per 2 moles glucosamine) of the t-butyldimethylsilylether of 3-hydroxytetradecanoic acid me-thylester could be identified (26). 

We then focused on the synthesis of lipid A analogs which contain 3-hydroxy fatty acids. For this purpose, sufficient amount of (R)-3-hydroxytetradecanoic acid ( ), which is the commonest hydroxy acid in Salmonella lipid A, was first prepared by means of an asymmetric reduction of the corresponding keto ester, i. ., methyl 3-oxotetradecanoate (j ) (7). Catalytic hydrogenation of 21 in the presence of Raney Ni modified with (R, R)-tartaric acid foaBr (8) afforded the crude (R)-ester in 85% enantiomeric excess. After saponification, the resultant acid was purified through its dicyclohexylammonium salt to give the optically and chemically pure (R)-acid In a yield of 61% from... 

There is also a monoclinic chain-packing subcell with all chain planes parallel, M, and it is shown together with the triclinic, r in Fig. 8.5. This chain packing has been observed in 3-thiado-decanoic acid (Abrahamsson and Westerdahl, 1965), in monoglycerides (Larsson, 1964), and in 2DL-hydroxytetradecanoic acid (Dahlen et aL, 1972). The dimensions of M in the hydroxy fatty acids are a = 4.30 A, fc = 4.74 A, c = 2.54 A and y = 110.9°. This symmetry is P2tlm, and the cross-section area per chain is 19.04 A. ... 

In the course of screening for inhibitors of cyclic adenosine-3, 5 -monophosphate phosphodiesterase, a strain of B. subtilis was found to produce a series of such inhibitors. These compounds with a m.p. of 136-139 °C and an optical rotation of -h 37° to 38.5° (chloroform), — 33° to — 38° (methanol), were lipopeptides with the same peptide moiety as surfactin. Their fatty acid components were 3-hydroxy-ll-methyldodecanoic acid, 3-hydroxy-10-methyldodecanoic add, 3-hydroxytetradecanoic acid (the major component), 3-hydroxy-13-methyltetradecanoic acid (the same acid as that of surfactin) and 3-hydroxy-12-methyltetradecanoic acid (707, 702). The location of the lactone ring was established by the same method as that used for surfactin 96), Therefore these inhibitors had structures quite similar to, and for one of them identical with, that of surfactin (40). 

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