5- Acetyl-4-methylthiazole

Acetamido-4-methylthiazole does not react with acetyl chloride in the Friedel-Crafts reaction (172. 407, 449). 

It should be noted that Grignard reagents obtained from 2-methylthiazole do not yield acetyl derivatives (31). Ketones can also be obtained from cyanothiazoles and Grignard reagents (87). Thus phenyl magnesium bromide and 5-cyanothiazole give phenyl 5-thiazolyl ketone (Scheme 35). 

Disposition in the Body. Rapidly absorbed after oral administration but extensively metabolised. A considerable number of metabolites have been identified in small quantities in urine. Less than 5% of a dose is excreted unchanged in the urine, and up to about 14% is excreted as 4-methylthiazole-5-acetic acid. Other metabolites identified in the urine include 5-(l-hydroxy-2-chloroethyl)-4-methylthiazole and 5-(2-hydroxyethyl)thiazole-4-carbolactone (which appear to be more abundant than 4-methylthiazole-5-acetic acid), together with 5-acetyl-4-methyl-thiazole, 5-(l-hydroxyethyl)-4-methylthiazole, and 5-(2-hydroxy-ethyl)-4-methylthiazole in both free and conjugated forms. 5-Ethyl-2-hydroxy-4-methylthiazole has been found in the tissues following overdoses of chlormethiazole. 5-(l-Hydroxyethyl)-4-methylthiazole and 5-acetyl-4-methylthiazole may be present in the plasma at concentrations similar to, or greater than those of unchanged drug. 

The organoleptic importance of alkylthiazoles was already recognized in 1966 (Arnold et al.) when they were isolated for the first time in food aromas. They play an important role, for instance, in the flavors of roasted cocoa beans, in roasted peanut flavor (Ho et al., 1983b) and in cooked beef flavor (Chang et al., 1977). They were found for the first time in coffee by Stoll et al. (1967) who identified 2-acetyl-4-methylthiazole (M.26) and 2-propionyl-4-methylthiazole (M-27). 

M.26) Ethanone, l-(4-methyl-2-thiazolyl)-, l-(4-methylthiazol-2-yl)ethanone, l-(4-methyl-l,3-thiazol-2-yl)ethanone, 2-acetyl-4-methylthiazole [7533-07-5[... 

The aroma of coffee is very complex and virtually none of the above mentioned constituents provides the typical aroma by itself. Exceptions are 2-furanmethanethiol and 5-methyl-2-furanmethanethiol that have odours reminiscent of coffee. In freshly roasted coffee, 2-furanmethanethiol is present in an amount ranging from 0.01 to 0.5 p.g/kg. A highly efficient sulfur-containing substance is also 2-methyl-3-furanthiol arising from thiamine. An important heterocyclic compound is 2-acetyl-4-methylthiazole and diterpene kahweofuran. 

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