Sherry lactone

An important y-lactone in wines is 5-oxohexano-4-lactone known as solerone, which recalls the smell of wine. It occurs as a mixture of (R)- (8-108) and (S)-enantiomers. The reduced form of solerone with a fruity odour, 4,5-dihydroxyhexano-4-lactone, is known under the trivial name of solerole or sherry lactone as it occurs in sherry-type wines, as a mixture of (4R,5R)- (8-109) and (4S,5S)-diastereoisomers. The almost racemic composition of solerone and solerole is attributed to racemisation during wine storage. An important lactone related to phthaUdes is 3fl,4,5,7fl-tetrahydro-3,6-dimethyl-3f/-benzofuran-2-one, also... 

Other lactones detected include a-butyrolactone and pantolactone (2,4-hydroxy-3,3-dimethylbutyrolactone), both of which are typical of sherries. Besides the duration of aging, their concentration is closely linked to yeast strain (Zea et al., 1995). Another lactone, solerone (4-... 

Lactones derived from oak constitute an important flavorant in most wines aged in barrel. However, because sherries are aged in cask that are rarely emptied or cleaned, they derive few lactones from the wood. Their detection is possible only in stages containing the oldest wine (Chatonnet et ah, 1990). 

The aroma of botrytized wines has been studied more extensively than that of the grapes. Mashuda et ah (1984) identified the lactone sotolon (4,5-dimethyl-3-hydroxy-2,(5)-furanone) as a principal compound in a botrytized aroma. Sotolon is also a key aroma compound in flor wines, for example, vin jaune, sherry (Dubois et ah, 1976 Martin and Etievant, 1991 Moreno et ah, 2005). However, Sponholz and Hiihn (1993) found no correlation between the degree of Botrytis infection and sotolon... 

Other lactones detected include a-butyrolactone and pantonolactone (2,4-dihyd-roxy-3,3-dimethylbutyrolactone), which is deemed typical of sherry wines. Both have been associated with specific yeast races (Zea et al. 1995) and the aging time (Cortes 2002). 

Wurz, R. E. M., Kepner, R. E., Webb, A. D. (1988) The biosynthesis of certain gamma-lactones from glutamic acid by film yeast activity on the surface of Flor Sherry. American Journal of... 

The biogenesis of solerone 1 and related compounds was successfully rationalized by biomimetic model reactions. As key step we established the pyruvate decarboxylase catalyzed acyloin condensation of pyruvic acid with ethyl 4-oxobutanoate 4 or ethyl 2-oxoglutarate 3 with acetaldehyde. The importance of the ethyl ester function in 3 and 4 serving as substrates for the enzymatic formation of a-hydroxy ketones 5 and 6 was demonstrated. The identification of six yet unknown sherry compounds including acyloins 5 and 6, which have been synthesized for the first time, confirmed the relevance of the biosynthetic pathway. Application of MDGC-MS allowed the enantiodifferentiation of a-ketols and related lactones in complex sherry samples and disclosed details of their biogenetic relationship. 

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