Thiazole green

Fig. 14.7 Synthesis of thiazole green 34 (TAG) used for low-level detection of DNA restriction fragment by CE.

Thiazole green represents another class of carbocyanines, which was recently utilized in the low-level detection of DNA restriction fragments by Soper et al. [74]. This dye is comprised of a quinolinium and a thiazolium nucleus joined by a pen-tamethine chain. The synthetic route to the thiazole green 34 is shown in Fig. 14.7. 2-Methylbenzothiazole 29 was allowed to react with methyl iodide to give the N-methyl derivative 30 which was further treated with malonaldehyde-dianil hydrochloride to afford the intermediate product 31. The intermediate product 31 was then allowed to react with N-(3-iodopropyl)lepidinium iodide 33, which had been obtained from the reaction of lepidine with 1,3-diiodopropane, to finally afford the asymmetrical thiazole green 34. 

Kuzemko, M.A., Van Arnum, S.D., Niemczyk, H.J. (2007) A Green Chemistry Comparative Analysis of the Syntheses of ( )-4-Cyclobutyl-2-2-(3-Nitrophenyl)Ethenyl Thiazole, Ro 24-5904. Organic Process Research Development, 11, 470-476. 

Upstream migrating glass eels also swim toward compounds with earthy and green (vegetable) odors. These are pyrazines, thiazoles, and alcohols of the cyclohexanol type (Sola, 1995). One of these compounds, 2-isobutyl-3-methoxypyrazine, is common in rivers and lakes (Hwang eta/., 1984). 

Oxazoles have been found in relatively few cooked foods, although over 30 have been reported in coffee and cocoa, and 9 in cooked meat. Oxazolines have been found in cooked meat and roast peanuts, but not to any extent in other foods. 2,4,5-Trimethyl-3-oxazoline has been regularly detected in cooked meat [26], and when it was first identified in boiled beef [27] it was thought that the compound possessed the characteristic meat aroma however, on synthesis it was shown to have a woody, musty, green flavour with a threshold value of 1 mg/kg [28]. Other 3-oxazolines have nutty, sweet or vegetable-like aromas and the oxazoles also appear to be green and vegetable-like [28]. The contribution of these compounds to the overall aroma of heated foods is probably not as important as the closely related thiazoles and thiazolines. 

Most cooked foods contain thiazoles. Simple alkyl-substituted thiazoles generally have odour threshold values in the range 1-1,000 pg/kg. Odour descriptions include green, vegetable-like, cocoa, nutty, and some are claimed to have meaty characteristics [22]. Although most alkylthiazoles result from thermal... 

Incorporation of the thiazole and thiophene rings into the donor portion of the azo dye molecule as in (108) and (109) also results in a bathochromic shift, the former dye being green and the latter violet, absorbing at 554 nm (emax 50 000dm3moF1 cm-1), a bathochromic shift of 75 nm when compared with the iso-7r-electronic p-dimethylaminophenyl systems, which has been explained in terms of the easier ionizability of the thienyl residue (78C323). 

Thiazoles are in a certain way unique they contain a heterocyclic ring containing both nitrogen and sulfur. Most of the thiazoles have been isolated from coffee and meat. The alkyl derivatives are most common they generally have green, nutty, and vegetable-like odors. 

Fig. 8 Overlap of the three pharmacophores representing the interactions found for paclitaxel in the 1JFF structure (A), epothilone A in the NMR-derived structure (B), and epothilone A in the QSAR model from Botta and co-workers (C), respectively. Blue C7-OH (epothilones) oxetane ring (paclitaxel) red C13 carbon (epothilones) phenyl ring (paclitaxel) yellow Cl carbonyl oxygen (epothilones) Cl carbonyl oxygen (paclitaxel) purple thiazole ring (epothilone) C3 benzamide (paclitaxel). (3-tubulin monomer is represented as a green cartoon and residues involved in hydrogen bonds are in orange (hydrogens are omitted for sake of clarity)...

Table 7 lists the oxazoles and thiazoles identified in the sample of cocoa butter. They were present only in roasted cocoa butter. The sensory characteristics of these compounds shown in Table 7 indicated that oxazoles and thiazoles possessed interesting green, fatty, sweet, and nutty sensory qualities and were high-impact flavor... 

Golich, T. G., Thomsen, J. R., Green, D. L. and Jersild, J. Determination of minor impurities of (R)-l-acetoxymethyl-3-(7-[(l-N,N-dimethylcarbamoyl)-6-(4-fluorophenyl)-indol-3-oyl]-lH, 3H-pyrrolo[l,2-c]thiazol-3-yl)pyridinium chloride by high performance liquid chromatography. J. Liq. Chromatogr. 18 4107-4116, 1995. 

Under basic conditions thiamine degrades to 5-(2-hydroxyethyl)-4-methylthiazole (45, sulfurol) and the pyrimidine derivative 46 [71]. Sulfurol is used in compounded flavourings in the flavour industry. It is almost odourless as such [73] however, it can decompose giving rise to thiazole and its derivatives such as 4-methylthiazole (47), 4,5-dimethylthiazole (48), 4-methyl-5-ethylthiazole (49) and 4-methyl-5-vinylthia-zole (50) ]71, 74], which possess nutty, green notes [75]. 

CIC The powerful odour is dominated by 2-isobutyl thiazole and 3-pentanethiol. The green notes are lipid degradation products like (E)-2-hexenal, hexanal and higher unsaturated aldehydes, the pineapple-pear like fruity notes are derived from methyl hexanoate, ethyl-2-hexenoate and hexyl acetate. The spicy cinnamon notes are represented by 3-phenyl propyl acetate, cinnamyl acetate, methyl cinnamate, ethyl cinna-mate and ciimamaldehyde. Gamma-decalactone and 2,5-dimethyl-4-hydroxy-furan-3(2H)-one and 3-hydroxy-2-butanone add the sweet, creamy body. Beta-famesene, citronellol, 2-phenylethanol, beta-ionone add the sweet, floral, quincelike part and methyl benzoate and ethyl benzoate impart a characteristic medicinal, exotic topnote. 

Thiazoles 2-acetyl thiazole imparts a roasted, crusty (bread crust, meat crust) note. Trimethyl thiazole has a nutty, green, cocoa note. 

CIC (Z)-3-hexenal and 2-(2-methylpropyl)thiazole form the fresh, green, vegetable topnote and a trace of damascenone is responsible for the floral background. On cooking, the fresh note from (Z)-3-hexenal is covered by the sweet sulphurous note of dimethyl sulfide. In canned tomatoes, the sulphurous note is supported by the spicy, dove-like aroma of 4-vinyl guaiacol and eugenol. 

Properties A yellow basic dye of the thiazole class, fluoresces yellow to yellowish-green when excited by UV. 

In 1887 Green prepared Primuline, formula (7), which was the first of the Thiazole direct dyes. 

Figure 4.3 compares the number of compounds identified in green and in roasted coffee beans. Green coffee contains a larger number of identified alcohols (B) and nearly the same number of identified aldehydes (C) and esters (F) than roasted beans. On the contrary, the latter are richer in furans (I), pyrazines (O), ketones (D) and phenols (H). Thiophenes (J), oxazoles (L) and thiazoles (M) have only been identified in roasted coffee. The roasting effect is also revealed by the increased number of pyrroles (K) and sulfur-containing compounds. The distribution of aroma volatiles is shown in Figure 4.4. 

Guava flavor G.f., resembling pear and quince flavor, contains )8- caryophyllene, numerous fruit esters, e.g., ethyl butanoate and ethyl hexanoate, cinna-myl acetate (see cassia oil) and the green notes from hexanal, ( )-2- hexenal, and (Z)-3- hexen-l-ol. Important trace components are C -C,g-dienals, Fura-neol, some pyrazines and thiazoles, as well as 6-mercapto-I-hexanol(CiHnOS, Mr 134.24,CAS [1633-78-9]) ... 

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