Fatty acids allylic hydroxylation

All unsaturated fatty acids contain highly reactive allylic positions, which are easily attacked by hydroxyl and peroxyl free radicals. Bielski et al. [3] studied the reactivity of unsaturated acid with perhydroxyl radical by the stopped flow technique. These authors... 

Dimorphotheca The seed of Dimorphotheca pluvialis is not very rich in oil (13-28%, typically about 20%), but it contains an unusual Cjg hydroxy fatty acid ( 60%) with hydroxyl group adjacent (allylic) to a conjugated diene system. This is very unstable and easily dehydrates to a mixture of conjugated 18 3 acids (105). 

Oliw, E.H., l.D. Brodowsky, L. Hornsten, and M. Hamberg (1993). Bis-allylic hydroxylation of polyunsaturated fatty acids by hepatic monooxygenases and its relation to the enzymatic and nonen-zymatic formation of conjugated hydroxy fatty acids. Arch. Biochem. Biophys. 300, 434-439. 

Consider a cell membrane lipid derived from linoleic acid, which is an unsaturated fatty acid. Hydrogen atom abstraction of an allylic hydrogen by a hydroxyl radical leads to a resonance-stabilized free allylic radical in which the unpaired electron is delocalized over C-9, C-11, and C-13. 

The 3-amino group can be easily AT-acylated to give acrylamide or fatty acid esters [110]. Silyation of 3-ketosucrose at the free hydroxyl groups with chlorotrimethyl silane provides a derivative that can be modified by Grignard-type reactions introducing allyl or alkyl chains onto the carbohydrate ring [110] (reaction 4.107). 

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