18-hydroxy-9,10-epoxystearic acid

Cutin is composed chiefly of a C16 and/or a Cis family of monomers (Fig. 4.2). The usual components of the former are palmitic acid, 16-hydroxypalmitic acid, and 10,16-dihy-droxypalmitic and/or its positional isomers in which the midchain hydroxyl group is at C9, Cs, or C7. Monomers that could be derived from the above acids by further oxidation or reduction also have been found in cutin from some plants. The C18 family consists of stearic acid, oleic acid, linoleic acid, 18-hydroxyoleic acid, 18-hydroxy-9,10-epoxystearic acid, and 9,10,18-trihydroxystearic acid together with their A-12 unsaturated analogs. Members of the Cie family are the dominant components of the cutin of fast-growing plants, whereas the cutin of slower-growing plants with a thicker cuticle consists of a mixture of C16 and C18 monomers (Harwood, 1980). 

On prolonged storage, even at 0-5 °C, unsaturated acids in seeds are oxidized to hydroxy and epoxy acids. The regiospecific and stereospecific nature of these reactions suggests that they are under enzymic control. For example, sunflower seeds generate 9,10-epoxystearic acid and 9,10-epoxyoctadec-12-enoic acid, both in optically active form. 

Croteau R, Kolattukudy P E 1975 Biosynthesis of hydroxy fatty acid polymers. Enzymatic epox-idation of 18-hydroxy oleic acid to 18-hydroxy-cis-9,10-epoxystearic acid by a particulate preparation from spinach Spinacia oleracea). Arch Biochem Biophys 170 61-72... 

Kolattukudy P E, Walton T J, Kushwaha R P S 1973 Biosynthesis of the Cjg family of cutin acids cu-hydroxyoleic acid, o>-hydroxy-9,10-epoxystearic acid, 9,10,18-trihydroxystearic acid, and the J -unsaturated analogs. Biochemistry 12 4488-4498... 

A soln. of cw-9,10-epoxystearic acid in benzene added dropwise with stirring during 10 min. to a soln. of 2,4,6-trinitrobenzenesulfonic acid in anhydrous dimethyl sulfoxide, stirring continued 15 min., stirred into excess cold ether-ethyl acetate (2 1), the solvent layer decanted, and the oily lower layer stirred 12-14 hrs. with water /hreo-9,10-dihydroxystearic acid. Y 65-70%. Also erythro- from trans-isomer, and prepn. of f. l-hydroxy-2-(alkoxysulfonium) salts, s. M. A. Khud-dus and D. Swern, Tetrah. Let. 1971, 411. 

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