Oxazoles compounds

A number of oxazole derivatives were also synthesised, of which (508) was among the most potent (IC50 = 80 nM). In general however, the binding affinities reported for the oxazole compounds were at best modest, and comparable with the related imidazole NH series (data not shown). 

The biologically active oxazole compounds were synthesized by Wang et al. [34], and two types of isomers were described those with N1 pointing towards the A-ring (e.g., 54) and those with N1 positioned closest to the B-ring (e.g., 55), Scheme 10. Tosmic reagents 12 and 13 were used for this synthesis as described in Sect. 2.1.1, Scheme 1. The chemistry described... 

The formation of methyl-oxazole compounds was also described by Wang et al. [34] utilizing an analog of the keto-enol intermediate (22) described in Sect. 2.1.1, Scheme 2. Scheme 11 shows the synthesis of compound 57 which exhibits anti-tubulin activity of 7.7. iM [34], In addition, a range of oxazole COX-2 inhibitors has been reported by Hashimoto et al. [55] employing similar chemistry. 

Oxazole compounds can also be produced by use of the Stille reaction. Clapham and Sutherland describe the use of tri-2-furylphosphine/Pd2(dba)3-catalyzed Stille coupling reactions (Scheme 12) to produce a range of oxazole-containing derivatives, including 58, with an 85% yield [56]. 

The synthesis of the oxazole compound 45 starts with the coupling of the N-protected (/ )-methylcysteine compound 18 with threonine terf-butyl ester using bis(2-oxo-3-oxazolidi-nyl)phosphinyl chloride (BOP-Cl) [15] as a coupling reagent. Jones oxidation of the threonine hydroxy group leads to the ketoamide 44. The desired oxazole ring is closed by treatment with thionylchloride/pyridine. After deprotection, the oxazole, compound 45 is obtained. In the next step the oxazole compound 45 is coupled with the tris(thiazoline) compound 43 to yield the thioester 46. Now Fukuyama closes the fourth and last thiazoline ring (46 47). After conversion of the carboxylic acid function into a methyl-... 

The synthetic strategy of the thiangazole synthesis of Pattenden [7] is similar to the strategy of the tantazole B synthesis of Fukuyama. The oligo(thiazoline) compound and the oxazole compound are synthesized separately. At the end, the two compounds are coupled to give the last... 

Cyclocondensation of the nitrile 62 with the (/ )-2-methylcysteine building block 5b provides the thiazoline ester 63. After conversion of the ester to the nitrile 64, cyclocondensation with 5b leads to the bis(thiazoline) 65. The subsequent conversion of the ester to the nitrile function (65 66) nearly failed, with 10 % yield. In the last synthetic sequence the bis(thiazo-line) compound 66 is coupled with the oxazole compound 61 to provide the third and last thiazoline ring. Formation of the methylamide is the final step of the thiangazole synthesis of Patten-den. 

The mass spectrometry of oxazole compounds has been reviewed by Traldi ef al. <1980H(14)847>. The main fragmentation pathway for most oxazole rings is shown in Scheme 1. Radical cation formation is followed by cleavage of the 0-C(2) bond, and then sequential loss of CO and HCN or nitrile <19920MS317>. 

Fluorescent brightening agents Anionic, cationic, or nonionic stilbene, triazine, cou-marin, and oxazole compounds. 

Depending on the formed intermediates, the photoreactions of five-membered heteroaromatic compounds may be classified into two types, these involving formation of cyclopropenyl ketones and Dewar intermediates. However, there are some reactions where both types of intermediates participate. Kojima and his coworker showed that both isomers should be taken into account in the photoreaction of an 1,3-oxazole compound (116)ll6). 

In the rat model of hypercalcemia all oxazole compounds were substantially less active than calcitriol, offering the chance to establish a therapeutic window in vivo. 

Of the 1,2-oxazole compounds, the arylhydrazone-l,2-oxazole derivatives exhibit high antifungal activity (Summers et al., 1968 Matolcsy et al., 1969 Eckhard et al., 1973). 

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