Steroidal oxazoles

Shafiullah and Ansari " found the steroidal oximes 320 to be useful starting materials for preparing the steroidal oxazoles 322 (Scheme 1.87). The authors also isolated small amounts of the corresponding ketones 323. 

Miscellaneous Heterocyclic Steroids.—I3-Aza-15-thia-I8-norequilenin, 11-oxo-15,l6-diaza-equilenin, and 18-nor-equilenin analogues as well as ring-A-furan, oxazine, and oxazole analogues of equilenin have been synthesised. The preparation of the thiadiaza-steroids (481) has also been briefly reported. 

Derivatives of ketones—including oximes, imines, and hydrazones— have served as precursors to oxazoles, although many examples of such conversions are described for steroidal and other fused ring systems. A few examples of steroidal and fused heterocyclic oxazoles and monocyclic analogs are described in this section. 

Unhindered aliphatic carboxylic acids such as those found in steroidal side-chains can be degraded by three carbons by a four-step procedure (Scheme 11), via dihydro-oxazole formation, dehydrogenation, and ozonolysis,which should be applicable to a good range of (saturated) substrates. 

Cornforth, Sir John Warcup (1917- ) Australian organic chemist. Cornforth is best known for his work on the problem of how the steroid cholesterol is synthesized in a cell. To investigate this problem he used the three isotopes of hydrogen - normal hydrogen (H-one), deuterium (H-two) and tritium (H-three) - and observed the different speeds of reactions found with these isotopes to infer how cholesterol was formed. He shared the 1975 Nobel Prize for chemistry with Vladimir PRELOG for this work. Cornforth has synthesized a number of other compounds including alkenes and oxazoles. 

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