Benzoxazole analogues

Name an important member of benzoxazole analogue employed as muscle relaxant. Give its one-step synthesis. 

Previous observations on the high reactivity of (benzoxazol-2-yl) thioesters toward various aminest prompted the development of uronium salts HSBTU (ll)t l as well as HATTU (13) and HAPyTU (29).t 9 However, HATTU and HAPyTU were less reactive and provoked more epimerization in both cyclization studies and fragment condensations than the corresponding oxygen analogues HATU (12) and HAPyU (28).f 9... 

As in CHEC-I <84CHEC-I(6)177>, the naming and numbering of oxazole and its derivatives follow the convention of Chemical Abstracts. The fully conjugated compounds are called oxazoles (1), benzoxazoles (2), oxazolium salts (3), and oxazole A -oxides (4). Hydroxy-substituted oxazoles exist in the oxo form, and there are five representatives the 2QH)-, 2(SH)-, 4(5//)-, 5(2//)-, and 5(4//)-oxazolones, (5)-(9) respectively. There are two mesoionic structures, the anhydro-4-hydroxy-oxazolium hydroxides (10) and the 5-hydroxy analogues (11), the latter of which are also referred to as the munchnones. Compound (12) is named 4,5-dihydrooxazole instead of A -oxazoline or 2-oxazoline, which is commonly used in the general literature. The other dihydrooxazoles include the less common 2,3- and 2,5-dihydrooxazoles, (13) and (14), respectively. The fully saturated compound... 

Treatment of 2-(phenacylthio)benzoxazole (333 R = Ph) with hydrazine hydrate results in cleavage of the oxazole ring and rearrangement via the spiro-intermediate (334) to the 677-1,3,4-thiadiazine (335) (Scheme 43). In contrast, the methyl analogue (333 R = Me) yields only the A-aminothiazole (336 86%) <82H(19)2119>. 

Hoffman, J.M., Smith, A.M., Rooney, C.S., et al. (1993) Synthesis and evaluation of 2-pyridone derivatives as HIV-1-specific reverse transcriptase inhibitors. 4. 3-[(Benzoxazol-2-yl) ethyl]-5-ethyI-6-methylpyridin-2(lH)-one and analogues. J. Med. Chem. 36 953-966. 

Two structural analogues of benzoxazole have gained prominence as potent muscle relaxants. Examples Chlorzoxazone Zoxazolamine. 

Semi-synthesis. From a selective cleavage of the oxazole ring we have worked out a semi synthetic approach in several steps which provided suitably designed analogues,closely related with respect to their overall stereochemistry,with only the benzoxazole ring substituents modified (8). 

The first example of a four-membered boron-nitrogen-sulphur heterocycle (32) has been prepared and characterized [reaction (12)], whereas the reaction of diborane with benzoxazole and its sulphur and selenium analogues produced benzoxazaboroles, benzothiazaboroles, and benzoselenazaboroles. ... 

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