Oxathiane, passion fruit

The impact of commercial yeast strains on wine fermentation leads to the formation of metabolites of yellow passion fruit (Passiflora edulis Sims) 2-methyl-4-propyl-l,3-oxathian 79 (10MI282,98JAFC1076,98MI53). This oxathian exists in four enantiomeric forms, 79a-d, and there are pronounced sensory differences between them (06CRV4099) for their enan-tioselective synthesis, cf. (84HCA947, 85LA1185). It should be mentioned that most of the aforementioned sulfur heterocycles are sold worldwide as fragrances and flavors. 

G. Singer, G. Heusinger, O. Frbhlich, P. Schreier and A. Mosandl. Chirality evaluation of 2-methyl-4-propyl-l,3-oxathiane from the yellow passion fruit. J. Agric. Food Chem., 34, 1029-1033 (1986). 

In 1976 Winter et al. (22) identified 3-methylthio-hexanol and a mixture of (Z)- and (E)-2-methyl-1,3-oxa-thiane in yellow passion fruit. 3-Methylthiohexanol possesses a green fatty and sulfury note and imparts the character of fresh fruit to the juice of passion fruits. The oxathianes were described as key compounds for the typical aroma of passion fruit and the (Z)-isomer had a stronger flavor. Pickenhagen and Bronner-Schindler (23) synthesized the enantiomers of (+)- and (-)-(Z)-2-methyl-... 

Passion fruit Red Rf. (Passiflora edulis) . The flowery-fruity flavor is due in particular to (Z)-3-hexenyl esters, (Z)-3-octenyl acetate, citronellyl and geranyl acetate. Yellow P.f. (P. edulis flavicarpa). 2-Methy 1-4-propyl-1,3-oxathiane, 3-mercapto-l-hexanol (CjHuOS, Mr 134.24, CAS [51755-83-0]) and the corresponding esters are mainly responsible for the exotic-fruity flavor. In both sorts about 30 Cu-noriso-prenoids, including fl ionone, )3- damascenone and edulane (2,5,5,8a-tetramethyl-l-benzopyran) make major contributions to the aroma. 

The following S-containing aroma substances have been isolated from the yellow fruit 3-methylthiohexane-l-ol which probably gives rise to 2-methyl-4-propyl-l,3-oxathianes (cis/trans isomers in the ratio of 10 1) (Xa, b Formula 18.39). Of the two cis isomers, only the 2R,4S-isomer (Xb), which has a sulfurous herb-like odor (threshold = 4 pg/kg water), has been found in the fruit. However, the aroma note more typical of passion fruit is exhibited by the 2S,4R-isomer (Xa). 

Additionally, aroma components of some foods are six-membered heterocycles containing an oxygen atom and sulfur in the molecule. An example of such a compound is (2J ,4S)-2-methyl-4-propyl-l,3-oxathiane (8-168), also known as ds-tropathiane, which occurs in the yellow passion fruit Passiflora edulis, f. flavicarpa, Passifloraceae), pineapple Ananas comosus, Bromeliaceae), whisky and white wines. 

The tropical category is one of the most important areas for new discoveries of key impact flavor compounds. Analyses of passion fruit and durian flavors have produced identifications of many potent sulfur aroma compounds (18). Among these is fropathiane, 2-methyl-4-propyl-l,3-oxathiane, which has an odor threshold of 3 ppb (15). For pineapple, 2-propenyl hexanoate (allyl caproate) exhibits a typical pineapple character (11) however, Furaneol, ethyl 3-methyl-thiopropionate, and ethyl-2-methylbutyrate are important supporting character impact compounds (31). The latter ester contributes the background apple note to pineapple flavor. Another character impact compound, allyl 3-cyclohexyl-... 

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