Free and glycosidically bound volatiles from pineapple juice were isolated and separated by means of an Amberlite XAD-2 column. Volatile compounds from bound fractions were released by almond d-glucosidase hydrolysis. By use of 7-valerolactone as internal standard, volatile components of free and bound fractions were determined by GC and GC-MS. Glycosidically bound 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF), phenols, lactones, alcohols, acids, and aldehydes were observed in pineapple for the first time. Phosphatase was also used to hydrolyze the bound fraction, but no volatile compounds were released. Glycosidically bound DMHF was further confirmed by HPLC analysis.

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Volatile components were isolated from Welsh onions and scallions by steam distillation at atmospheric pressure and analyzed by GC and GC-MS. Sulfur-containing compounds account for 87 % and 82 % of the total volatiles in the distilled oils of Welsh onions and scallions, respectively. In addition to the sulfur compounds commonly reported in the genus Allium, 41 novel volatile sulfur-containing components were found in the distilled oils of green onions. The novel compounds can be grouped as (1) 1-[alk-(en)ylthio]alkyl alk(en)yl disulfides, (2) alkyl tetra-or pentathiaalkanes or alkene(@, and (3) thiaheterocycles. Heat may be responsible for the formation of many of the sulfur-containing volatiles in green onion distilled oils. Some of the novel polysulfides identified have sweet, scallion-like or onion-like odors.

2-[[(2-Methoxy-4-formylphenoxy)carbonyl]oxy]-4pentanol (8). The synthesis of 8 was conducted on a 0.02-mol scale using the conditions described for 1, starting with the aryl chloroformate (derived from 2-methoxy-4formylphenol) and 2,4-pentanediol. NMR, IR, and TLC data indicate the product is formed. However, a pure sample could not be isolated due to contamination by the phenolic and cyclic carbonate components. The inability to isolate a pure sample indicates rapid decomposition during isolation.l-[(Phenoxycarbonyl)oxy]glycerol (9). To 25 mL of 10% acetic acid was added 1.5 g (0.006 mol) of l-0-(phenoxycarbonyl)-2,3-0-isopropylideneglycerol (Pfeiffer, 1970). The emulsion was stirred vigorously and heated to 60 °C for 2 h. The solution was cooled to room temperature and extracted several times with petroleum ether and then ethyl ether. The ethyl ether layer was washed with aqueous saturated sodium bicarbonate and dried over anhydrous MgS04, followed by evaporation of the solvent under reduced pressure to yield a liquid. NMR, IR, and TLC data indicate the product was formed, however, like 8, was unstable.l-[[(2-Methoxy-4-methylphenoxy)carbonyl]oxy]glycerol (10). The synthesis of 10 was conducted on a 5-mmol scale using the conditions described for 9, starting with l-0-[(2-methoxy-4-methylphenoxy)carbonyl]-2,3-0isopropylideneglycerol (Pfeiffer, 1970). NMR, IR, and TLC data indicate the product was formed, however, like 8, was unstable. l-[[(2-Methoxyphenoxy)carbonyl]oxy]-2-ethanol(11). The synthesis of 11 was conducted on a 0.01-mol scale using the conditions described for 1, starting with the aryl chloroformate (derived from 2-methoxyphenol) and 1,2-ethanediol. NMR, IR, and TLC data indicate the product was formed, however, like 8, was unstable.Thermolysis of the Aryl Hydroxyalkyl Carbonates (1-7). A 10-50-mg sample of each of the aryl hydroxyalkyl carbonates was thermolyzed in a sealed tube under the specific conditions listed in Table I. The yield of released phenolic component in each case was determined by GC quantitation with an authentic sample. ACKNOWLEDGMENT I thank Dr. Geoffrey Chan and Dr. Yoram Houminer for helpful discussions, Dot Seal for secretarial assistance, and Ronald C. Bassfield for NMR spectral analysis.

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