Dihydrosterculic acid

Diglycosyldiphytanylglycerol diether, 158 Dihydroperoxides, 455 Dihydrosphingosine, 281,439 Dihydroxystearic acids, 57 Dihydrosterculic acid, 53 Dihydroxy acetone phosphate, 504 Dihydroxyhexadecanoic acid, 44 Diimine, 452 Dilatation, 253,254,374 Dilaurin, 366,367... 

Dihydro-PGE, in D-OOl 52 (+)-l 1-epi-Dihydro-PGEi, in D-OOl52 18-Dihydrorenierin see B-00012 Dihydrosphingosine, in A-00017 Dihydrosterculic acid, in 0-00221... 

Figure 5.1 Structures of naturally occurring cyclic fatty acids. I, Cyclopropane acids a, 9,10-methylenehexadecanoic acid b, 11,12-methyleneoctadecanoic (lactobacillic) acid c, 8,9-methy-leneheptadecanoic (dihydromalvalic) acid d, 9,10-methyleneoctadecanoic (dihydrosterculic) acid. II, Mycolic (2-alkyl-3-hydroxy) acid. Ill, Cyclopropene acids a, 9,10-methyleneoctadec-9-enoic (sterculic) acid b, 8,9-methyleneheptadec-8-enoic (malvalic) acid. IV, Cyclopentenyl acids a, ll-cyclopent-2-enyl-undecanoic (hydnocarpic) acid b, 13-cyclopent-2-enyl-tridecanoic (chaulmoogric) acid c, 13-cyclopent-2-enyl-tridec-6-enoic (gorlic) acid. V a, 11-cyclohexyl-undecanoic acid b, 11-cycloheptylundecanoic acid.

Figure 5.6 Mass spectrum (25 eV) of picolinyl ester derivative of 9,10-cyclopropaneoctadecanoic (dihydrosterculic) acid. Redrawn from Harvey, D. J., Picolinyl derivatives for the characterization of cyclopropane fatty acids by mass spectrometry, Biomed. Mass Spectrum., 11 (4), 187-92, 1984.

While the transformation of oleic acid to dihydrosterculic acid and desaturation of the latter to sterculic acid were clearly established, the route of biosynthesis of the homologous cyclopropanoid and cyclopropenoid fatty acids could not be deduced from the results of experiments with seedlings and seed slices (Johnson et al., 1967 Hooper and Law, 1965). It appeared likely that dihydromalvalic acid was the immediate precursor of malvalic acid (Johnson et al., 1967), but it was not apparent whether dihydromalvalic acid was formed from a heptadecenoic acid or by a-oxidation of dihydrosterculic acid. The latter possibility appeared more likely in view of the labeling pattern of sterculic and malvalic acids isolated from H. syriacus seedlings that had been incubated with [l- C]acetate (Smith and Bu Lock, 1964). 

The results of labeling experiments in tissues and callus cultures of various Malva species indicate the sequence of reactions in Fig. 3 for the biosynthesis of fatty acids containing a three-membered carbocyclic ring (Yano et al., 1972a). Oleic acid is converted to dihydrosterculic acid, methionine, presumably as S-adenosylmethionine, being the methylene donor. The desat-... 

It is as yet unknown whether the substrates of the enzymes involved in the synthesis of dihydrosterculic acid are specific phospholipids, acyl-CoA, acyl-acyl carrier protein (ACP) or even free fatty acids. The preferred substrates of bacterial cyclopropanoid fatty acid synthesis are phosphatidyl-ethanolamines (Christie, 1970 O Leary, 1965 Hofmann, 1%3 Law, 1971). The true substrate of the desaturating enzyme is also yet to be identified. It is well known that exogenous stearic acid, a straight-chain saturated fatty acid, is not desaturated to oleic acid unless it is supplied as the ACP derivative (Shine et al., 1976). In contrast, dihydrosterculic acid, a cyclic saturated fatty acid, is desaturated to stercuiic acid when supplied as such. 

Figure 5.14. Analysis of kapok seed oil methyl esters after reaction with silver nitrate in anhydrous methanol, on a glass WCOT column coated with Carbowax 20M, maintained at 190°C with hydrogen as carrier gas [99]. Abbreviations 18 CA, dihydromalvalic acid 19 CA, dihydrosterculic acid 18 CM, methoxy derivatives of malvalic acid 19 CM, methoxy derivatives of sterculic acid 18 CC, enone derivatives of malvalic acid 19 CC, enone derivatives of sterculic acid. (Reproduced by kind permission of the authors and of Analytical Chemistry, and redrawn from the original paper).

Diastereoisomerism, 369,371-72 Diastereotopic tritons, 190 1,1-Diazene, 232 Diffusion coefficients, 72 Diffusion constant (D), 101-102 Diffusion, discrete, 156-58 Dihydrosterculic acid, 166 Dilute spins, 344,361-62 p-Diraethoxybenzene, 105 DimethyIcadmium, 467,470,491,507 Dimethyl ormamide, 104-105 1,4-Dinitrosopiperazine, 93 Dipolar order, 128-30 Dipolar relaxation see Relaxation, dipole-dipole Dipole-dipole interaction broadening by, 117-21 coupling by, 51-52,112-15,143 [16- H]Diprenorphine, 181 DNA, 155-56,235-36,325-26 DNMR5, 92... 

The biosynthesis of cyclopropane and the related cyclopropene acids in higher plants has been studied by experiments with radioactive precursors. In this method, a supposed precursor for the compounds being studied is supplied to the plant and its incorporation into more complex molecules and/or conversion to products is studied at successive time intervals. The sequence in which the radiolabel appears in different compounds can be used to deduce the pathways by which they are made. Thus it has been deduced that oleic acid gives rise to the cyclopropane derivative of stearic acid (dihydrosterculic acid). The latter can either be shortened by... 

---