Y-hydroxylactone

Use of RuOj/aq. Na(IO )/CCl to oxidise the secondary alcohol function in hydroxylactones gave ketolactones, while lactones gave ketocarboxylates [201-203], The former reaction is exemplified by 5-ejco-enrfo-dihydroxybicyclo[2.2.1] heptane-2-e (i(9carboxylic acid-y-lactone giving the 5-keto-6-endo product (Fig. 2.9). A number of other hydroxylactones were similarly oxidised, as were y- or 5-hydroxycarboxylates to ketocarboxylates [201]. 

Garbe L-A, Tressl R (2004) Metabolism of deuterated t/jreo-dihydroxy fatty acids in Saccha-romyces cerevisiae Enantioselective formation and characterization of hydroxylactones and y-lactones. Helv Chim Acta 87 180... 

Not only acids but also a-hydroxylactones (y- and S-) when submitted to the system DIB-iodine underwent oxidative decarboxylation, accompanied by -fragmentation. This reaction took place under non-photochemical conditions in various solvents, at 20-58°C. The substrates - mainly sugar derivatives - eventually yielded, after a mechanistically interesting route, j8-iodo or a,/ -unsaturated compounds. An example follows [71] ... 

A simple and efficient method was developed by E.A. Couladouros and co-workers for the synthesis of optically pure five- or six-membered hydroxylactones. The method begins from y-butyrolactone and uses the following key transformations reduction, Wittig-Schiosser reaction. Sharpless asymmetric dihydroxylatlon, oxidation, and lactoniza-tion. The preparation of antitumor agent (-)-muricatacin was achieved in 6 steps and in 43% overall yield. 

A soln. of phthalic anhydride and Na-trichloroacetate in anhydrous 1,2-di-methoxyethane refluxed 20 min. with stirring, more solvent added after thick paste has formed, heating continued 45 min., the resulting salt treated with water, filtered, and acidified with HGl 3-hydroxy-3-trichloromethylphthalide. Y 80%. F. e. and ring-chain tautomerism between a)-hydroxylactones and ketocarboxylic acids s. A. Winston et al., J. Org. Ghem. 30, 2784 (1965). 

Other lactones can also be used. a-Bromo-y-butyrolactone (2.26) was converted to hydroxylactone 2.27.1 jhe lactone ring was opened by potassium phthalimide to give 2.28 and removal of the phthalimido group gave 2-hydroxy-4-aminobutanoic acid (2.29). 

The y-lactones (55h, i, j, and k) which carry oxygen-containing substituents in position 4 are found exclusively in alcoholic beverages, except for hydroxylactone (55h) which also occurs in tomatoes 561), Owing to its distinct vinous smell, solerone (55i) is a particularly typical representative of this series 607), The occurrence and the mode of formation of lactones in various wines and in other alcoholic beverages are described in several review articles 400, 547, 609),... 

Aroxyacoxy compds. a-Diketone monoketals Enolperoxides Glycidic acid esters a-Hydroxyacetals 1-Hydroxylactones a-Ketoacetals a-Keto-Y-lactones Lactolesters... 

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