Thiazolidines and their oxidation products as flavouring compounds

FLAVOUR AND FRAGRANCE JOURNALFlavour Fragr. J. 2002; 17: 432–439Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ffj.1121

Thiazolidines and their oxidation products as flavouringcompounds

Xavier Fernandez,1 Elisabet Dunach,2* Roland Fellous,1 Louisette Lizzani-Cuvelier1 and Michel Loiseau1

1 Laboratoire Aromes, Syntheses, Interactions, Faculte des Sciences de Nice Sophia-Antipolis, Parc Valrose, 06108 Nice cedex 2,France2 Laboratoire de Chimie Bioorganique, CNRS, UMR 6001, Faculte des Sciences de Nice Sophia-Antipolis, Parc Valrose, 06108 Nicecedex 2, France

Received 24 October 2001Revised 16 January 2002Accepted 22 January 2002

ABSTRACT: The selective oxidation reactions of thiazolidines were studied. The synthesis of 2- and 3-thiazolines,as well as that of thiazoles, thiazolidine-1-oxides and thiazolidine-1,1-dioxides, are presented. Olfactory analysisof several of these compounds reveals interesting notes with thresholds in the ppm range, in most cases relatedto foodstuffs. Copyright 2002 John Wiley & Sons, Ltd.

KEY WORDS: thiazolidine; 2- and 3-thiazoline; thiazolidine-1-oxide; thiazolidine-1,1-dioxide; oxidation, flavour

Introduction

Recently identified as trace compounds in guava,1 thi-azolidines are used as flavouring agents in variousfoods. These compounds have not been often identi-fied in natural products. Lee et al.2 could identify 2-methyl-thiazolidine and 2-propyl-thiazolidine in heatedbutter aroma. These products were proposed to be pro-duced during cooking by the condensation reactionof cysteamine (2-aminoethanethiol) and acetaldehyde orbutyraldehyde.3

These volatile thiazolidine derivatives (2-alkyl-thiazolidines) are used as flavouring agents in variousfoods, such as soups, sauces and beverages.4,5

Thiazolidines may produce a spectrum of olfactorynotes, ranging from fruity, green and vegetable-like(onion, radish, bean, asparagus) to nutty, butter-likefatty, caramel, or to smoky, spicy and meat or fish-like,depending on the type of substitution in the heterocyclicring.6 They are introduced in low concentrations,generally 0.1–10 ppm, alone or with other flavouringcompounds.4

Thiazolines and thiazoles are more used as flavour-ing compounds. More than 30 thiazoline structures haveso far been identified from natural sources and food,particularly in cooked meat7 and certain exotic fruits,such as lychees.8 There has also been considerableindustrial interest in these compounds, due to their

* Correspondence to: Elisabet Dunach, Laboratoire de Chimie Bioor-ganique, CNRS, UMR 6001, Faculte des Sciences de Nice Sophia-Antipolis, Parc Valrose, 06108 Nice cedex 2, France.

ability to enhance the flavour and/or aroma of vari-ous consumable materials, including foodstuffs. In thisrespect, 2,4,5-trisubstitued-3-thiazolines (R D alkyl orH) are widely used as flavouring materials. These com-pounds present a roasted meat, vegetable or chocolatearoma with astringent, roasted or nutty flavour.9 2-Alkylthioalkyl-4,5-dialkyl-3-thiazolines have also beendescribed to increase or enhance the nutty, bready orvegetable (tomato, potato) flavour or aroma characteris-tics of several foodstuffs.10

The biosynthesis of 2-isobutyl-thiazole in tomatoesreported by Schutte11 suggests that this compound wasformed from the oxidation of the corresponding thiazo-lidine with a thiazoline intermediate (Scheme 1). Thisproposed mechanism indicates the strategic importanceof the thiazolidine ring in flavour chemistry. These con-siderations allow us to study these thiazolidine hete-rocycles, 1, and their oxidation products: 2- and 3-thiazolines, 2 and 3; thiazoles, 4; thiazolidine-1-oxides,6; and thiazolidine-1,1-dioxides, 7.

Experimental

GC–MS

GC–MS analysis was accomplished by using a HP 5890gas chromatograph under the following operational con-ditions: carrier gas, He; injector and detector tempera-tures, 250 °C; injected volume, 0.2 µl; split ratio, 1 : 100;HP1 column, polydimethylsiloxane (50 m ð 0.20 i.d.,film thickness, 0.50 µm; pressure, 100 kPa); temperature

Copyright 2002 John Wiley & Sons, Ltd.

THIAZOLIDINES AND OXIDATION PRODUCTS AS FLAVOURINGS 433

2-isobutyl-thiazole

+

N

S

iBu

N

S

iBu

i-C4H9CH(NH2)COOH

iBu

HO

SH

NH2

+−CO2

SH

NH2HOOC

N

S

iBu

HN

S

iBu[O]

Scheme 1. 2-Isobutyl-thiazole biosynthesis proposed by Schutte

program, 60–220 °C at 4 °C/min, then 220 °C for 25 min,coupled to a 5970A mass selective detector. Mass spec-tra were obtained by electron ionization at 70 eV, m/z35–400, source temperature 250 °C; only the most abun-dant ions are given.

1H- and 13C-NMR

1H- and 13C-NMR spectra were recorded on a Bruker AC200 FT spectrometer at room temperature, with 40 mgproduct in 0.5 ml CDCl3, with TMS as internal standard.

Reagents and Solvents

All solvents and reagents were purchased from com-mercial suppliers and used as received, unless otherwiseindicated. Chromatographic separations were performedusing 70–260 mesh (SDS) silica gel eluted with distilledsolvents. Thin-layer chromatography was carried out onSDS precoated silica plates (60/15 µm layer thickness).Aluminium oxide, activated, neutral, STD grade, 150mesh, 58 A, was purchased from Sigma-Aldrich. Man-ganese dioxide (MnO2), used for 3-thiazoline synthesis,was a manganese (IV) oxide, <10 µm, 90%C suitablefor use in batteries, was also purchased from Sigma-Aldrich.

Thiazolidine (1) Synthesis12

To a stirred solution of (L)-cysteine methyl, ethyl, iso-propyl ester hydrochloride or cysteamine (10 mmol) andpotassium acetate (0.98 g 10 mmol) in methanol, ethanolor isopropanol (30 ml), a solution of freshly distilledaldehyde in 10 ml alcohol was added at 0 °C. After stir-ring for 4 h at 0 °C, the reaction mixture was filtered

off and the solvent evaporated under reduced pressure.The crude product was washed with a saturated solutionof aqueous NaCl (15 ml) and extracted three times withCH2Cl2 (3 ð 15 ml). The organic phase was dried overMgSO4 and the solvent evaporated. A colourless oil wasobtained.

2-Methyl-thiazolidine (1a), 60% yield; 2-ethyl-thiazolidine (1b), 65% yield; 2-isopropyl-thiazolidine(1c), 70% yield; ethyl thiazolidine-4(R)-carboxylate(1d), 90% yield; methyl 2-methyl-thiazolidine-4(R)-carboxylate (1e), 90% yield; methyl 2-ethyl-thiazolidine-4(R)-carboxylate (1f), 85% yield; methyl 2-isopropylyl-thiazolidine-4(R)-carboxylate (1g), 80% yield; ethyl 2-methyl-thiazolidine-4(R)-carboxylate (1h), 86% yield;ethyl 2-ethyl-thiazolidine-4(R)-carboxylate (1i), 91%yield; ethyl 2-propyl-thiazolidine-4(R)-carboxylate (1j),83% yield; ethyl 2-isopropyl-thiazolidine-4(R)-carboxy-late (1k), 85% yield; isopropyl 2-isopropyl-thiazolidine-4(R)-carboxylate (1m), 80% yield. NMR data for thesecompounds have already been reported.1,13–15

2-Thiazoline (2) Synthesis

Thiazolidines (1) (4 mmol) were stirred in CH3CN(8 ml) in the presence of RuCl2�PPh3�3 (0.4 mmol).tert-Butyl hydroperoxide (4 mmol) in 10 ml solventwas slowly added into the solution and the reactionwas followed by GC. The crude mixture was fil-tered over aluminium oxide and washed with aque-ous Na2SO4 solution (2 ð 10 ml) and aqueous KI (5%,2 ð 10 ml). Solvent evaporation was followed by purifi-cation by column chromatography with silica gel, withcyclohexane : ethyl acetate (8 : 2) mixture as the eluent.

2-Methyl-2-thiazoline (2a), 40% yield; 2-isopropyl-2-thiazoline (2c), 67% yield; ethyl 2-methyl-2-thiazoline-4(R)-carboxylate (2h), 45% yield. NMR data for thesecompounds have already been reported.16,17

Copyright 2002 John Wiley & Sons, Ltd. Flavour Fragr. J. 2002; 17: 432–439

434 X. FERNANDEZ ET AL.

Ethyl 2-isopropyl-2-thiazoline-4(R)-carboxylate (2k),64% yield. New compound. 1H-NMR: 1.2 (d, 6H, J D6.9 Hz), 1.25 (t, 3H, J D 7.2 Hz), 2.9 (1H, septuplet,J D 6.9 Hz), 3.5 (dd, 2H, J D 4 and 9.2 Hz), 4.2 (q,2H, J D 7.2 Hz), 5(td, 1H, H-4, J D 1 and 9.2 Hz).

13C-NMR: 14.34, 21.29, 34.24, 34.99, 61.89, 78.01,171.59, 180.89.

3-Thiazoline (3) and Thiazole (4) Synthesis

Thiazolidine 1 (5 mmol) was stirred in CH3CN (50 ml)in the presence of MnO2 (15–17 equivalents). The reac-tion was followed by GC or TLC. The crude mix-ture was filtered over Celite. Solvent evaporation wasfollowed by purification by column chromatographyon silica gel, with hexane : ether mixture as eluent.With longer reaction times or higher oxidant quanti-ties (20 equivalents) the corresponding thiazoles, 4, wereobtained with good yields.

Methyl 2-ethyl-3-thiazoline-4-carboxylate (3f), 55%yield; methyl 2-isopropyl-3-thiazoline-4-carboxylate(3g), 56% yield; ethyl 2-methyl-3-thiazoline-4-carboxy-late (3h), 50% yield; ethyl 2-ethyl-3-thiazoline-4-carboxylate (3i), 68% yield; ethyl 2-isopropyl-3-thiazoline-4-carboxylate (3k), 58% yield; isopropyl 2-isopropyl-3-thiazoline-4-carboxylate (3m), 56% yield.We have already described spectral data of these newcompounds.15

Ethyl thiazole-4-carboxylate (4d), 60% yield; ethyl 2-propyl-thiazole-4-carboxylate (4j), 59% yield. NMR datafor these compounds have already been reported.18

3-Acetylated Thiazolidine (5) Synthesis

Thiazolidines 1 (10 mmol) were stirred in CH2Cl2(20 ml) in the presence of K2CO3 (10 mmol). Aceticanhydride (1 equivalent) in 10 ml solvent was slowlyadded into the solution and the reaction was followedby TLC. The crude mixture was filtered off and washedwith a saturated solution of aqueous NaCl (15 ml) andextracted three times with CH2Cl2 (3 ð 15 ml). Theorganic phase was dried over MgSO4 and the solventevaporated. A colourless oil was obtained. 5b, 5e and 5iare new compounds.

3-Acetyl-2-ethyl-thiazolidine (5b) as a mixture of twoisomers: 93% yield. 1H-NMR: 0.95 (2t, 6H, J D 7.3and 7.4 Hz), 1.6–2 (m, 4H), 2.1(s, 3H), 2.15(s, 3H),3(m, 2H), 3.45 (m, 1H), 3.7 and 3.85 (2m, 2H), 4.4(m, 1H), 4.85 (dd, 1H, J D 4.8 and 9.2 Hz), 5.25(dd,1H, J D 4.1 and 8.7 Hz). 13C-NMR: 10.88, 11.02, 22.27,23.37, 29.29, 29.52, 30.14, 31.53, 47.04, 50.13, 64.61,65.53, 168.28.

Methyl 3-acetyl-2-methyl-thiazolidine-4(R)-carboxylate (5e) as a mixture of two isomers: 80% yield.

1H-NMR: 1.55(d, 3H, J D 6.2 Hz), 1.65 (d, 3H, J D6.4 Hz), 2.1 (s, 3H), 2.2 (s, 3H), 3.4 (m, 4H), 3.8 (s,3H), 3.85 (s, 3H), 4.75 (dd, 1H, J D 4.1 and 5.2 Hz), 5(t, 1H, J D 7.6 Hz), 5.65 (q, 1H, J D 6.4 Hz), 5.5 (q,1H, J D 6.2 Hz). 13C-NMR: 22.09, 22.50, 23.38, 24.66,32.16, 33.74, 52.76, 53.17, 59.83, 60.20, 62.59, 63.55,168.11, 168.59, 171.23.

Ethyl 3-acetyl-2-ethyl-thiazolidine-4(R)-carboxylate(5i) as a mixture of two isomers: 70% yield. 1H-NMR:0.9 (2t, 6H, J D 7.2 Hz), 1.25 (2t, 6H, J D 7 Hz), 1.4and 1.8 (2m, 4H), 2.1 (2s, 6H), 3.2 (dd, 2H, J D 4.1and 13.4 Hz), 3.3 (m, 2H), 4.1 (m, 4H), 4.65 (dd, 1H,J D 5.2 and 7 Hz), 4,8 (t, 1H, J D 5 Hz), 4.95 (dd,1H), 5.35 (dd, 1H, J D 4.5 and 9.4 Hz). 13C-NMR:13.60, 13.75, 14.27, 22.16, 23.15, 31.87, 33.59, 38.37,39.37, 61.70, 62.37, 63.40, 64.75, 65.64, 168.17, 168.69,170.79, 171.57.

Thiazolidine-1-oxide (6) Synthesis

3-Acetylated-thiazolidine 5 (5 mmol) was stirred at 0 °Cin a mixture MeOH : H2O (1 : 1, 20 ml). Sodium meta-periodate (1 equivalent) was slowly added into the solu-tion and the reaction was followed by GC (2–4 h). Thecrude mixture was filtered off and extracted three timeswith CH2Cl2 (3 ð 15 ml). Solvent evaporation was fol-lowed by purification by column chromatography withsilica gel, with ethyl acetate : methanol (8 : 2) mixture asthe eluent.

Methyl 3-acetyl-2-methyl-thiazolidine-1-oxide-4(R)-carboxylate (6e) was obtained as a mixture of fourisomers in 61% yield. New compound.

1H-NMR: 1.4 (d, J D 7.2 Hz), 1.45 (2d, J D7.2 Hz), 1.6 (d, J D 6.8 Hz), 2.1-2.2 (4s), 3 (dd, J D10.3 and 14.4 Hz), 3.2 (dd, J D 9.4 and 14.4 Hz), 3.6(m), 3.75-3.85 (4s), 5 (qd, J D 1.5 and 7.2 Hz), 5.1-5.4 (m), 5.65 (qd). 13C-NMR: 16.02, 17.2, 22.1, 53.12,53.59, 59.43, 59.65, 68.21, 78.14, 78.95, 169.73, 172.35.

Thiazolidine-1,1-dioxide (7) Synthesis

3-Acetylated-thiazolidine 5 (5 mmol) was stirred atroom temperature in acetone (40 ml). Potassium per-manganate (2 equivalents) was added into the solutionand the reaction was stirred overnight. The crude mix-ture was filtered off, dried over MgSO4 and the solventevaporated. Methyl 3-acetyl-2-methyl-thiazolidine-1,1-dioxide-4(R)-carboxylate (7e) was obtained as a mixtureof two isomers: 70% yield. New compound.

1H-NMR: 1.55 (d, 3H, J D 6.8 Hz), 1.7 (d, 3H, J D7 Hz), 2,2 (s, 3H), 2,25 (s, 3H), 3,4 (dd, 1H, J D 8.4and 13.8 Hz), 3.65 (m, 3H), 3.8 (s, 3H), 3.85 (s, 3H), 4.7(q, 1H, J D 7 Hz), 5 (q, 1H, J D 6.8 Hz). 13C-NMR:17.67, 21.94, 47.89, 53.42, 67.86, 69.48, 169.43, 172.01.



Organoleptic Tests

Flavour was evaluated by a trained panel of six skilledtasters: three flavourists (Degussa Flavor & Fruit Sys-tems) and three perfumers. Compounds were dilutedin ethanolic solutions at 1%. Taste was evaluated bythe same three flavourists. Solutions were prepared inethanol at 1% weight concentration and diluted with dis-tilled water and saccharose (5%) to a concentration of1 ppm.

Determination of Odour Threshold

Stock solutions were prepared in ethanol and dilutedstepwise with EtOH at concentrations of 0.1–1000 ppm.Sensory evaluation was carried out by 16 untrainedtasters. The threshold value was defined as the lowerconcentration perceived by at least 50% of the panel.Results were verified by a triangular cup-tasting, takingtwice alcohol as the reference.

Results and discussion

Thiazolidines, 1, were easily obtained in 60–91% yieldsfrom the condensation of (L)- or (R)-cysteine ethyl,methyl esters or cysteamine (2-aminoethanethiol) or theirammonium salts and an alkyl aldehyde derivative underslightly basic conditions (Scheme 2).

In the reaction with (L)-cysteine esters, the cyclisationgives rise to a new chiral centre at the C-2 position ofthe heterocyclic ring. A mixture of two cis- and trans-diastereomers can therefore be obtained.

Previous literature data reported the possibility of anepimerization reaction involving carbon 2, via an imine-thiol intermediate.19,20 Therefore, these two diastere-omers cannot be separated; further, reactions and olfac-tory tests with these compounds 1, were made with theisomer mixtures.

We examined selective oxidation reactions of thethiazolidine ring (Scheme 3). Thus, a series of 2-thiazolines, 2, was prepared in 40–67% yield by aRu-catalysed/TBHP oxidation of 1. Compounds 2 wereobtained with good regioselectivities (>95%).21 Werecently proposed a novel strategy for the synthesisof 4-carboxy-substituted 3-thiazolines, 3, in whichthiazolidines 1 were selectively oxidized to 3-thiazolinesby manganese dioxide (MnO2) in 50–68% yield.15,22

This series of 3-thiazolines, possessing an estersubstituent at the 4-position, had not, to our knowledge,been described before. With the same MnO2 oxidant,thiazoles, 4, could be obtained in good yields usinglonger reaction times.

Sulphur oxidation of compounds 1 did not occur inthe presence of the secondary amine. All previously

reported thiazolidine-1-oxides have structures with aprotected nitrogen in the thiazolidine ring.23 Interest-ingly, a natural product that incorporates the thiazoli-dine sulphoxide moiety has been reported and it con-tains an acetylated nitrogen.24 Thiazolidines, 1, weretherefore acetylated to afford derivatives, 5, before pro-ceeding to sulphur oxidation. Thiazolidine-1-oxides, 6,were prepared using m-chloroperbenzoic acid (m-CPBA)or sodium metaperiodate (NaIO4) as the oxidants, in50–61% yields. The best result was obtained usingNaIO4. Thiazolidine-1,1-dioxides, 7, were synthesizedwith good yields (60–70%), using potassium perman-ganate (KMnO4, 2 equivalents) or hydrogen peroxide(H2O2, 5 equivalents) in acetic acid.

Olfactory and gustative properties of some of thesynthesized compounds, 1–7, were determined usinga panel of experts in flavours or fragrances. To ourknowledge, organoleptic properties of the compoundsthat we tested have never been described, except for2-isopropyl-thiazolidine 2c.4

The olfactory properties were examined in ethano-lic solutions and the results are presented in Table 1.Thiazolidines 1 and 5 presented leguminous notes(entries 1–4), interesting for potential food appli-cations. Only ethyl 3-acetyl-2-ethyl-thiazolidine-4(R)-carboxylate (entry 5) presented sweetened properties ofbutter cookies-like, light but persistent. 2-Thiazolines, 2(entries 6–9) presented very powerful notes, essentiallymeat-like (roasted, grilled or cooked) or fruity. Ethylor methyl 3-thiazoline-4-carboxylates, 3 (entries 10–15)were described as possessing leguminous foodstuff prop-erties (fennel or leek-like, with aniseed back note), orsweetened.

Thiazoles, 4 (entries 16 and 17) presented weaknotes within the tested concentrations. Thiazolidine-1-oxide, 6 (entry 18) and thiazolidine-1,1-dioxide, 7(entry 19) presented essentially woody-like, weak notes.The weakness of compounds 4, 6 and 7 suggests thepossibility of testing these products at much higherconcentrations.

The most interesting compounds were defined as verypowerful olfactory agents. Their olfactory threshold wasevaluated for five of these more interesting compounds(Figure 1). For all compounds 1–3 tested, the olfactorythreshold was under 10 ppm (Figure 1). This value wasverified by triangular tests.

Gustatory properties were determined in sweet aque-ous solutions at 1 ppm concentrations (Table 2). Allthe compounds that we tested presented interestingfoodstuff properties. 2-Isopropyl-2-thiazoline (entry 5)seemed particularly interesting, presenting very power-ful green and fruity (peach) notes, comparable to thesyrup of this fruit. Olfactory and gustatory propertieswere comparable enough; only ethyl thiazolidine-4(R)-carboxylate 1d (Table 1, entry 2, and Table 2, entry 2)presented a very different taste and odour: there was a



1R1 = H, COOH, COOMe, COOEt, COOiPrR2 = H, alkyl R3 = H, alkyl, aryl

N

S

R1H

R2

R3ROHAcOK

R2

R3

O+

SH

NH2.HClR1

Scheme 2. Thiazolidine synthesis

76

5

4 3

2

1

R1 = COOEtR2 = H, nPr

R1 = COORR2 = AlkylR3 = H

N

S

R2

R1N

S R2

R3R1

R1 = H, COOEtR2 = Alkyl

CH3CNCH3CN, 50 - 60 °CMnO2 (20 equiv.) MnO2 (13 - 17 equiv.)

N

S

R1

R2

TBHP/Ru -catCH3CN, CH2Cl2

m-CPBA/CH2Cl2NaIO4/ MeOH:H2O (1:1)

KMnO4/ AcetoneH2O2/ CH3COOH

N

S

R1

R2

R3

R4

O

N

S

R1

R2

R3

R4

O

R1 = H, COORR2, R3 = H, AlkylR4 = AcN

S

R1

R2

R3

R4

Protection

N

S

R1

R2

R3

H

O

Scheme 3. Thiazolidine oxidations

very characteristic and persistent mushroom odour but adisappointing weak taste of burned cream. The study ofgustative properties of these series of heterocycles is tobe continued by testing other derivatives and by usingsalty solutions.

Conclusions

In conclusion, we have prepared a series of differentlysubstituted volatile thiazolidines and studied their oxida-tion reactions leading either to 2- or 3-thiazolines, thia-zoles, thiazolidine-1-oxydes or thiazolidine-1,1-dioxide.

These compounds were obtained in good to moder-ate yields.

The study of the olfactory and gustatory properties ofthese compounds indicated that thiazolidines 1 and 5,acetylated or not, as well as 2- and 3-thiazolines, 2, and3 presented generally foodstuff notes, very interestingfor potential food applications. They afforded thresholdsunder 10 ppm in ethanolic solutions. On the other hand,thiazoles, 4, thiazolidine-1-oxides, 6, and thiazoldine-1,1-dioxides, 7, presented weaker olfactory properties atthe tested concentrations.

Work is in progress to study the properties of thesecompounds further at different concentrations.



N

S iPr

H

HN

S

iPr

N

S

iPr

EtOOC N

S

iPrOOC

iPr

HN

S

EtOOC

iPr

H

1c 2c 2k 3m 3k

THRESHOLD STUDY

0

1

2

3

4

5

6

7

8

9

10

0,1 1 10 100 1000concentrations in ppm

subjectnumber

1c

2c

2k

3m

3k

Figure 1. Olfactory threshold

Table 1. Olfactory properties

Entry Compound GC–MS (%) Flavour(flavourist)

Flavour(perfumer)

1

HN

S iPr

H

1c 131(MC, 4.8), 88(100), 70(10.2), 61(9.8),55(6.7), 41(5.3), 39(3.8)

Very powerful, gas,shallot

Powerful, green, nerol,geraniol

2

HN

S

EtOOC

1d 161(MC, 16), 88(100), 86(13.5), 61(17.5),59(10.4), 41(12.3), 41(6.5)

Earthy, mushroom,fruity

Sweet, lightly aniseed,fennel

3

N

S

MeOOC

Me

H

H

1e 161(MC, 15.6), 146(29), 115(14.6),102(100), 87(17), 86(41), 85(56),75(74.7), 59(64.3), 55(52.2), 44(19.6)

Slight, fennel, garlic,onion

Green, grass cut

4

N

S

H

Et

Ac

5b 159(MC, 13.3), 130(40.1), 88(100),70(13.7), 43(33.4), 42(7.9), 41(7)

Onion, uncookedshallot, cooked meat

Green, fresh leek

5

N

S

AcEtOOC

Et

H

5i 231(MC, 1.2), 202(5.8), 161(8), 160(100),131(38.3), 116(30.7), 86(24.9),59(10.7), 43(44.5)

Cookies, vanilla, lightbut persistent

Woody, quinoleine,tobaccos, almond

(continued overleaf )



Table 1. (Continued)

Entry Compound GC–MS (%) Flavour(flavourist)

Flavour(perfumer)

6

N

S

Me

2a 101(MC, 76.6), 60(100), 59(50.6), 58(10),55(16.9), 54(8.6), 45(24.6), 42(13.5)

Very powerful, nuts,meat, metallic

Very powerful, woody,lightly camphored

7

N

S

iPr

2c 129(MC, 64.7), 128(17.6), 108(14.4),87(16.2), 86(100), 85(13.8), 83(19.5),82(18.9), 79(15.5), 74(22), 59(40)

Powerful and persistent,fruity, sweet, peach

Very powerful, green,camphored, medicinal

8

N

S

Me

EtOOC

2h 173(MC, 0.3), 100(100), 86(11), 59(41.3),58(9.6), 42(7.5)

Fruity, grilled meat,soup

Fruity, grapefruit,persistent

9

N

S

iPr

EtOOC

2k 187(MC, 1.5), 129(8.2), 128(100),113(5.4), 87(5.7), 86(39.1), 59(28.9),58(9.2)

Nuts, praline, green,cooked meat

Green, French bean(undecatriene), musty

10

N

S

MeOOC

Et

H

3f 173(MC, 45), 144(66), 114(23.9),113(14.7), 112(100), 100(11.7)59(52.1), 46(10.2), 45(21.6), 42(18.6),41(26.7)

Persistent, caramel,butter cookies

Woody, sufficientlypersistent

11

N

S

MeOOC

iPr

H

3g 187(MC, 28.4), 145(43.4), 144(11.6),113(100), 112(42.4), 85(16.6), 59(33),55(11.7), 45(12.5), 41(14.9)

Leguminous, leek,fennel

Leguminous, cabbage,aniseed

12

N

S

EtOOC

Me

H

3h 173(MC, 28.6), 158(72.4), 130(15.8),112(100), 100(15.9), 74(16.5), 73(13.2),68(13.2), 68(18.8)

Cookies, butter,sulphured

Basmati rice, jasmone

13

N

S

EtOOC

Et

H

3i 187(MC, 28.7), 130(14.6), 114(24.7),113(13.9), 112(100), 87(12), 86(35.8),82(11.3), 68(14.6), 59(12.6), 57(11),54(13), 45(17.3), 41(27.3)

Aniseed, fennel, grilled,very persistent

Aniseed, fresh

14

N

S

EtOOC

iPr

H

3k 201(MC, 28.6), 168(33.3), 158(29),154(33), 130(15.2), 128(32.7),126(17.7), 113(25), 112(100), 86(42.9),82(21), 55(19.8), 54(20.1), 45(17.4)

Sulphured, green,leguminous, leek,fennel

Liquorice, whisky

15

N

S

iPrOOC

iPr

H

3m 215(MC, 18.8), 130(27.3), 114(12.7),113(100), 112(41.5), 86(12.7), 85(10.6),55(17.3), 45(13), 43(65.8), 41(31.5)

Leguminous, vegetablesoup

Myrcene, geranium leaf

16

N

S

EtOOC

4d 157(MC, 9.2), 113(31.4), 112(100),85(56.8), 84(17.5), 58(9.7), 57(28.6),45(16.2)

Weak Weak, cade oil

17

N

S

EtOOC

nPr

4j 199(MC, 0.8), 172(9.5), 171(100),154(25.6), 138(13.8), 127(12.7),125(58.8), 57(12.8)

Weak, fennel, leek Earthy, musty

18

N

S

MeOOCAc

Me

H

O 6e 178(8.93), 177(100), 128(21.1), 118(14.5),117(14.4), 115(29.1), 114(19.9), 83(14),70(57.2), 69(16.6), 59(20.4), 55(20.5),54(17.3), 43(73.2), 42(13.6)

Weak Weak, woody, musty

19

N

S

MeOOCAc

Me

H

O O 7e 176(2.9), 129(52.7), 87(35.9), 70(99.8),55(15.2), 54(17.1), 43(100), 42(13.4)

Weak Mycene, geranium leaf



Table 2. Gustatory properties

Entry Compound Gustatory properties

1

N

S iPr

H

H

1c Cereal, malt, mayonnaise

2

N

S

EtOOCH

1d Caramel, tea, burned cream, weak

3

N

S

MeOOC

Me

H

H

1e Powder, creamy, caramel

4

N

S

AcEtOOC

Et

H

5i Onion, garlic, cooked meat

5

N

S

iPr

2c Green, fruity, ethereal, peach

6

N

S

Me

EtOOC

2f Ethereal, fruity

7

N

S

MeOOC

Et

H

3f Creamy

8

N

S

EtOOC

iPr

H

3k Earthy, leguminous, soup powerful

Acknowledgements—We are grateful for cooperation with DEGUSSAFlavors & Fruit Systems (Grasse) for the olfactive and gustative tests,and thank DESS Foqual promotion 2000–2001 for its contribution inthe threshold study.

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559.


Thiazolidines and their oxidation products as flavouring compounds

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