Methyl thioacetate

II x. h3c sch3 Methyl thioacetate II ch3ch2ch2 sch2ch3 Ethyl butanethioate (J Methyl cyclohexane-... 

Several of the lower molecular weight aliphatic compounds, in a mixture, are part of the roasted coffee aroma. A nine-compound mixture with roasted coffee aroma contained isopentane, n-hexane, acetaldehyde, dimethyl sulfide, propanal, isobutanal, isopentanal, methanol, and 2-methylfuran.20 In addition, the freshness of aroma and taste has been correlated with 2-methylpropanal and diacetyl. When the concentration of these falls off, so does the taste.21 Other aliphatic compounds that are steadily lost from ground roasted coffee, unless it is vacuum packaged, include methyl formate, methyl acetate, methyl thioacetate, and acetone.22 The concentrations in roast coffee for four compounds whose contribution to the fresh flavor have long been known are dimethyl sulfide (4 ppm), methyl formate (12 ppm), isobutanal (20 ppm), and diacetyl (40 ppm). The taste thresholds are 0.1, 0.5, 0.5, and 1.0 ppm, respectively, in the brew made with 5 g coffee per 100 ml water.15... 

In soft cheeses, such as Brie, Camembert, and Limburger, the following sulfur compounds were implicated 3-(methylthio)propanol, MT, DMS, DMDS, DMTS, dimethyl tetrasulfide, methyl ethyl disulfide, diethyl disulfide, 2,4-dithiapentane, 3-methylthio-2,4-dithiapentane, methional, 2,4,5-trithiahex-ane, 1,1-fe-methylmercaptodisulfide, methyl thioacetate (=methanethiol acetate), benzothiazole, methylthiobenzothiazole, methyl ethyl sulfonate, methyl methane thiosulfonate, thiophene 2-aldehyde, and H2S.34 Many of these were only present in small amounts Limburger cheese was notable for 13.2% of DMDS, 0.5% of methyl thioacetate, and 0.8% of DMTS. 

Sulfur-containing amino acids, especially L-methionine, serve as precursors for MT and the many materials derived from this compound, such as DMS, DMDS, DMTS, methyl thioacetate, etc. The most direct route for the L-methionine MT conversion is by demethiolation (Equation 4) catalyzed by methionine y-lyase, EC 4.4.1.11 ... 

In addition to bacterial conversion of L-methionine to cheese aroma compounds, certain cheese-ripening yeasts have been implicated. They include De-baromyces hansenii, Geotrichum candidum, and Yarrowia lipolytica, in addition to Kluyveromyces lactis and Saccharomyces cerevisiae (previously noted). Of these yeasts, Geotrichum candidum was most effective at producing sulfur compounds with the major product being S-methyl thioacetate, with smaller amounts of MT, DMS, DMDS, and DMTS. Kluyveromyces lactis had a similar profile, but produced a much smaller amount of S-methyl thioacetate than did G. candidum. S-Methyl thioacetate is formed by a reaction of MT and acetyl-CoA (Equation 7) ... 

The supply of MT may be rate-limiting in K. lactis. In addition to S-methyl thioacetate, G. candidum also contains S-methyl thiopropionate, S-methyl thiobutanoate, S-methyl thiowobutanoate, S-methyl thiowovalerate, and S-methyl thiohexanoate in smaller amounts.42... 

Fig. 7.10. Approximate charge distribution in methyl acetate and S-methyl thioacetate, as calculated by the INDO quantum-mechanical method [144]...

R. Hilal, A. M. El-Aaser, A Comparative Quantum Chemical Study of Methyl Acetate and 5-Methyl Thioacetate. Toward an Understanding of the Biochemical Reactivity of Esters of Coenzyme A , Biophys. Chem. 1985, 22, 145-150. 

Flomorex is a fluorocarbacepem. It is a structural analogue of cephalosporin, in which the 7/1-amine is acylated by 5-difluoromethyl thioacetic acid. This latter is prepared by reaction of CHF2CI with methyl thioacetate (Figure 8.22). ... 

Reaction between 74 and alkyl / -ketoacetates or acetylacetone under the same conditions, however, furnishes cyclic 1,1-enediamines 77 with loss of one acetyl group39. The evidence available indicates the involvement of a consecutive reaction between the initially formed 1,1-enediamines 75 and the methanethiol released at the condensation step97. The methanethiol attacks the more reactive carbonyl group of the enediamine 75 to form the intermediate 76, which undergoes elimination to give the deacetylation products 77 and methyl thioacetate (78) (Scheme 6). 75 can survive in this reaction... 

Oxathietane intermediates are proposed for the reaction of bis-trifluoro-methylthioketene with p-A/, A-dimethylaminobenzaldehyde, and for the reaction of bis-trifluoromethylketene with cyclic, five-membered thioureas, for example, 515. A 1-methyl-1,3-oxathietane salt is a possible intermediate in the thermolysis of 5-methoxymethyl thioacetate to 5-methyl thioacetate. ... 

El-Aasar, A. M. M., Nash, C. P., and Ingraham, L. L. Infrared and Raman spectra of S -methyl thioacetate toward an understanding of the biochemical reactivity of esters of coenzyme A. Biochemistry 21, 1972-1976 (1982). 

Problem 22.1 Draw structures for the enol lautoiners of the following compounds (a) Cyclopentanone (b) Methyl thioacetate (c) Ethyl acetate... 

The first group of sulphur compounds mentioned above can be defined as common fermentative sulphur volatiles (CFSV) and includes in our presentation ethylmercaptan (EtSH), dimethyl sulphide (DMS), diethyl sulphide (DES), dimethyl disulphide (DMDS), diethyl disulphide (DEDS), methyl thioacetate (MTA), ethyl thioacetate (ETA), 2-mercaptoethanol (ME), 2-(methylthio)-l-ethanol (MTE), 3-(methylthio)-l-propanol (MTP), 4-(methylthio)-l-butanol (MTB), benzothiazole (BT) and 5-(2-hydroxyethyl)-4-methylthiazole (HMT) (see Table 5.6). 

CIC In both melon types the lipid degradation products (Z)-6-nonenol, (Z,Z)-3,6-nonadienol and the corresponding aldehydes are responsible for the typical green, fatty, cucumber melon aspect. Ethyl propionate imparts an overripe character to muskmelon flavour, supported by the sweet, caramelic aspect of 2-methyl-5-ethyl-4-hydroxy-furan-3(2H)-one and the fmity-sulphurous aroma of S-methyl thioacetate and methyl thiobutyrate. 

Sulfurases produce free sulphur chemicals like hydrogen sulphide, methylmercapan, S-methyl thioacetate, S-methyl thiobutyrate. 

The presence of fixation of CO by minerals led to acetate, pyruvate, acetaldehyde, glycerol-aldehyde, acetone, methyl mercaptan (also called methanethiol), methyl-thioacetate, glycine, and aspartic acid. Alanine forms by reduction of pyruvate with ammonia. Iron sulfide and hydrogen sulfide reduce molecular nitrogen to ammonia according to the overall reaction ... 

Steric interactions dramatically increase the free energy difference for acetates and thioacetates. For example, AG° is respectively 9.3 and 4.9 kcal mol-1 for methyl acetate and methyl thioacetate, compared to AG° = 2.1 and 1.3 kcal moT1 for methyl formate and methyl thioformate respectively. In turn, the barrier to rotation remains the same order of magnitude with AGtE z = 12.4 (methyl acetate) and 10.1 kcal mol-1 (methyl thioacetate). 

Figure 5.2. Volatile sulfur compounds of wines (15) dimethyl sulfide, (16) ethylmer-captan, (17) diethyl sulfide, (18) methyl thioacetate, (19) dimethyl disulfide, (20) ethyl thioacetate, (21) diethyl disulfide, (22) 2-mercaptoethanol, (23) 2-(methylthio)-l-ethanol, (24) 3-(methylthio)-l-propanol, (25) 4-(methylthio)-l-butanol, (26) 3-mercap-tohexan-l-ol, (27) 4-methyl-4-mercaptopentan-2-one, (28) 3-mercaptohexanol acetate, (29) benzothiazole, (30) 5-(2-hydroxyethyl)-4-methylthiazole, (31) fra s-2-methylthio-phan-3-ol, (32) 2-methyltetrahydrothiophen-3-one.

Intramolecular aldol/Perkin type condensation of orf/to-formylaryloxyacetic acids and arylthioacetic esters produces benzofuran- and benzothiophene-2-esters respectively, as illustrated below. The synthesis can be performed in one pot, thus ortfto-hydroxyaryl-aldehydes or -ketones, are 0-alkylated with a-halo-ketones, then intramolecular aldol condensation in situ produces 2-acyl or 2-aroyl-benzofurans. ° For benzothiophenes, the ring-closure substrates can also be obtained via methyl thioacetate displacement of fluoride from orf/to-fluoro-araldehydes. ... 

Chloroacetic acid or methyl chloroacetate reacts with thioformylhydrazines by way of the isolable intermediates [(phenylhydrazono)methyl]thioacetic acid or methyl [(phenylhydrazono)-methyl]thioacetate to give 4-aryl-4/f-1,3,4-thiadiazin-5(6//)-ones.59 60 Cyclization of the intermediates is realized in the presence of, for example, dicyclohexylcarbodiimide. 

Method A A solution of sodium chloroacetate (11 mmol) in H20 (15mL) was added dropwise to the thioformylarylhydrazine (10 mmol) and NaOH (10 mmol) in H20 (15 mL) and the mixture stirred at 25 °C for 4 h. The mixture was then neutralized with 10% aq HC1, the precipitate collected, and recrystallized (MeCN) yield of [(arylhydrazono)methyl]thioacetic acid 72-78%. 

Method B To a mixture of the [(arylhydrazono)methyl]thioacetic acid (10 mmol) and NaOMe (10 mmol) in MeOH (15 mL) under N2 was added dropwise methyl chloroacetate (10 mmol), the mixture was stirred at 25 °C for 3 h and then evaporated in vacuo. The residue was extracted (3 x Et20) and the extract evaporated in vacuo to afford almost pure methyl carboxymethyl-Ai-anilinothioformimidate yield 89% mp 63 - 64 °C. 

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