Rationalizing the Formation of Damascenone: Synthesis and Hydrolysis of Damascenone Precursors and their Analogues, in both Aglycone and Glycoconjugate Forms

Abstract

. Food Chem. 2008, 56, 9183. In the first paragraph of the Discussion, the half-life values in parentheses should be interchanged, that is, the sentence in question should read as follows: "The hydrolytic data reported here show that the rates of formation of 1 from 6 (half-lives (t 1/2 ) of 40 and 65 h at pH 3.0 and 3.2, respectively) are lower than from 5 (half-lives of 32 and 48 h, respectively, at the same pH values) ( Table 1)."

Occurrence, Sensory Impact, Formation, and Fate of Damascenone in Grapes, Wines, and Other Foods and Beverages

“…The time for half of the alcohol 20 to be converted to damascenone was 40 h at pH 3.0 and 65 h at pH 3.2. 323 Hydrolysis of the various synthetic isomers of the diol 16 under the same conditions, however, also gave damascenone as the only major product, accompanied by trace amounts of C-9 adducts. The alcohol 20 was observed as an intermediate in the conversion, and no trace of 3-hydroxydamascone ( 14) was formed.…”

“…322 The conversion of diol 16 to damascenone was slightly faster than the conversion of alcohol 20, with half-lives of the former of 32 and 48 h at pH 3.0 and 3.2, respectively. 323 This meant that, although some of the damascenone generated from 16 was apparently being formed via 20, the latter was not an obligatory intermediate in the conversion, which proceeded via at least two pathways. Chiral analysis of the products of short-term hydrolysates of pure enantiomers of the diol 16 showed that the hydroxyl at C-3 was completely epimerized in recovered starting material, whereas the stereochemistry at C-9 remained intact.…”

“…322 The reactivity at C-9 was further examined in a similar study of model allenic alcohols 9 and 21 (Figure 4), which are desoxy analogues of the diol 16 and triol 4, respectively (Figure 4). 323 Compared to the triol 4 and diol 16, hydrolysis of 9 in 10% aqueous ethanol proceeded relatively slowly. At both 25 and 45 °C and pH 3, the enantiomerically pure forms of 9 gave isomeric dehydrotheaspiranes 8 as the only products, and chiral analysis of these products showed that there had been no epimerization at C-9 prior to cyclization.…”

Carotenoid and Chlorophyll‐Derived Compounds in Some Wine Grapes Grown in Apulian Region

“…Carotenoid degradation can give rise to different derivatives, each specific to the initial pigment and highly flavorant (Isoe and others 1973; Sefton and others 1989; Skouroumounis and others 1992; Daniel and others 2008). It was reported that norisoprenoids could originate from direct degradation of carotenoid molecules such as β‐carotene, lutein, neoxanthin, and violaxanthin (Wintheralter 1992; Ferreira and others, 2008).…”

Isolation, absolute configuration and bioactivities of megastigmanes or C13 isonorterpinoides

“…Ohloff et al, (1973) and Isoe et al, (1973) suggested that such a transposition could take place with allene intermediates. Ohloff et al hypothesized that damascenone (Ohloff et al, 1973) could be formed from an allenic triol (Skouroumounis et al, 2000) which derive from the known ketone (Sefton et al,1989) which could in turn be derived directly by enzymatic cleavage of neoxanthin (Daniel et al,2008). Damascenone basic structure is related to megastigmane, the only difference being at keto group present at C-7.…”