Shaoxiang Yang

Rapidly Responsive and Highly Selective Fluorescent Probe for Bisulfite Detection in Food

The new fluorescent probe 4-hydroxy-3-((2E,4E)-5-phenylpenta-2,4-dienoyl)-2H-chromen-2-one (probe 1) was designed and synthesized for selective detection of sulfite. The fluorescence intensity of the probe was decreased only in the presence of HSO3-; all other anions assessed resulted in an increased fluorescence response. Hence, probe 1 acts as a highly selective sensor for HSO3-. This sulfite sensitivity can also be readily monitored visually, as once treated with sulfite the solution shows a marked color change from yellow to colorless. Moreover, probe 1 can be conveniently used as a signal tool to determine the HSO3- levels in various sugar samples.

Enantioselective syntheses and sensory properties of 2-methyl-tetrahydrofuran-3-thiol acetates.

The enantioselective synthesis of four stereoisomers of 2-methyl-tetrahydrofuran-3-thiol acetate was achieved. The two enantiomers of the important intermediate cis-2-methyl-3-hydroxy-tetrahydrofuran were obtained by Sharpless asymmetric dihydroxylation (AD), whereas the two enantiomers of trans-2-methyl-3-hydroxy-tetrahydrofuran were derived from the corresponding optically active cis-isomers by Mitsunobu reaction. Each stereoisomer of 2-methyl-3-hydroxy-tetrahydrofuran went through mesylation and nucleophilic substitution to afford the corresponding product with specific configuration. (2R,3S)- and (2R,3R)-2-methyl-tetrahydrofuran-3-thiol acetate were obtained in 80% ee, whereas the (2S,3R)- and (2S,3S)-isomers were in 62% ee. The odor properties of the synthesized four stereoisomers were evaluated by gas chromatography-olfactometry (GC-O), which revealed perceptible differences among stereoisomers both in odor features and in intensities.

Highly selective and rapidly responsive fluorescent probe for hydrogen sulfide detection in wine

A new fluorescent probe 6-(2, 4-dinitrophenoxy)-2-naphthonitrile (probe 1) was designed and synthesized for the selective detection of hydrogen sulfide (H2S). The addition of H2S to a solution of probe 1 resulted in a marked fluorescence turn-on alongside a visual color change from colorless to light yellow. Importantly, this distinct color response indicated that probe 1 could be used as a visual sensor for H2S. Moreover, probe 1 was successfully used as a signal tool to determine the H2S levels in beer and red wine.

One-pot synthesis of (-)-Ambrox.

(−)-Ambrox is recognised as the prototype of all ambergris odorants. Widely used in perfumery, (−)-Ambrox is an important ingredient due to its unique scent and excellent fixative function. An environmentally friendly and practical preparation of (−)-Ambrox is still unavailable at present although a lot of attention has been paid to this hot research topic for many years. A one-pot synthesis of (−)-Ambrox was studied starting from (−)-sclareol through oxidation with hydrogen peroxide in the presence of a quaternary ammonium phosphomolybdate catalyst {[C5H5NC16H33] [H2PMo12O40]}, which gave the product a 20% overall yield.

Selective catalytic dehydration of furfuryl alcohol to 2, 2′-difurfuryl ether using a polyoxometalate catalyst

The spice flavour compound 2, 2′-difurfuryl ether (DFE) is widely utilised in the food industry as it has a coffee-like, nutty, earthy, mushroom-like odour. However, despite intensive research efforts, to date, an environmentally friendly and practical synthetic preparation technique for 2, 2′-difurfuryl ether is still unavailable. Here, we investigate a new approach using polyoxometalate catalysts to selectively catalytically dehydrate furfuryl alcohol to 2, 2′-difurfuryl ether. We have successfully applied this methodology using the polyoxometalate (POMs) catalyst {[(CH3CH2CH2CH2)4N]2[SMo12O40]} to produce 2,2′-difurfuryl ether in a 30.86% isolated yield.

Preparation and odour of cis - and trans -2-methyltetrahydrofuran-3-thiol acetates

The preparation of cis- and trans-2-methyltetrahydrofuran-3-thiol acetates from (E)-3-penten-1-ol is reported. The mesylate of (E)-3-penten-1-ol was converted into trans- or cis-2-methyl-3-hydroxytetrahydrofuran by oxidation with H2O2 and HCOOH or with KMnO4. cis- or trans-2-Methyltetrahydrofuran-3-thiol acetate was prepared by mesylation and an SN2 nucleophilic substitution with AcSH from trans- or cis-2-methyl-3-hydroxytetrahydrofuran respectively. The configuration of the products was confirmed by their synthesis. Olfactory evaluation of cis- and trans-2-methyltetrahydrofuran-3-thiol acetates indicated some differences both in odour feature and intensity.

Preparation and odour properties of (S)-3-mercapto-1-heptyl acetate

Synthesis of (S)-3-mercapto-1-heptyl acetate was achieved in four steps. Sharpless asymmetric epoxidation of (E)-2-heptenol yielded (2R,3R)-2,3-epoxy-1-heptanol, which was treated with thiourea in the presence of Ti(OPri)4 to give (2S,3S)-2,3-epithio-1-heptanol, reduction of which followed by acetylation afforded (S)-3-mercapto-1-heptyl acetate in 91% ee. The optically active product possessed a tropical fruit aroma reminiscent of mango and passion fruit, with berry, ester-like, sweet, and pepper-like aspects.

A Fluorescent Probe for Sensitive Detection of Hydrazine and Its Application in Red Wine and Water

A fluorescent probe, 7-(diethylamino)-2-oxo-2H-chromene-4-carbaldehyde (probe 1), was designed and synthesized for the sensitive detection of hydrazine. The addition of N2H4 caused the fluorescence intensity of probe 1 to decrease. The probes fluorescence was turn-off after adding N2H4, which could be observed under UV light at 365 nm. Moreover, once treated with different concentrations N2H4 solutions, the solution color change could be distinguished, which indicates that probe 1 could be used as a visual sensor for hydrazine. Moreover, probe 1 can be used as a signal tool to determine hydrazine levels in solutions, such as red wine and water.

Characterisation of a by-product formed in the industrial production of γ -nonalactone

Distillation residues from the industrial production of γ-nonalactone, which is accomplished by reaction of hexanol with methyl acrylate initiated by t-butyl peroxide, yielded a by-product which we deduced to be 4-(methoxycarbonylethyl)-g-nonalactone. The possible pathway of formation of this by-product is discussed.