Functionalization of the angular methyl

SELECTIVE FUNCTIONALIZATION OF THE ANGULAR METHYL GROUP AND FURTHER TRANSFORMATION TO 19-NORSTEROIDS... 

N-chloroamine functionalization of the angular methyl group preparation of 3/3-hydroxy-18-chloro-20a-methylamino-5a-pregnan-l l-one trifluoroacetate, 259... 

Lead tetraacetate functionalization of the angular methyl group... 

II. Functionalization of the Angular Methyl Groups / 237 General principles of substitution / 237 Lead tetraacetate oxidations / 240 Hypohalite reactions / 246 Photolysis of nitrites (Barton reaction) / 253 A-Chloroamine reactions (Hoffmann-Lofller reaction) / 257 Ketone irradiations / 260 Summary / 264... 

The synthesis of (+)-pisiferic acid (1) presents many important aspects (i) functionalization of the angular methyl group to lactone, (ii) cleavage of lactone ring to carboxylic acid, and (iii) conversion of (78) to allylic alcohol (81) via iron carbonyl complex... 

Remote functionalization of the angular methyl group in santonin derivatives has also been accomplished using the Barton reaction. For example a key step in the previously reported synthesis of the norsesquiterpenoid rishitin (450) from tetrahydro-a-santonin (443) involves photochemical transformation of the nitrite ester (447) to the oxime (448) (c/. Scheme 46). Rishitin (450) is a well known antifungal phytoalexin produced by diseased potato tubers and recent studies... 

Ethers have been prepared by the thermal lead tetraaeetate method in 60-71% ° yield. Introduction of an axial 3a-acetoxy function into 5a-H steroids, however, seems to change the conformation of ring A in such a way that the distance of the 2/ -oxygen from the angular methyl group is considerably increased. Consequently the 2/5,19-ether is formed in only 0.7% to 24% yield. " 02... 

Synthetic Applications of the Diels-Alder Reaction. Diels-Alder reactions have long played an important role in synthetic organic chemistry.74 The reaction of a substituted benzoquinone and 1,3-butadiene, for example, was the first step in one of the early syntheses of steroids. The angular methyl group was introduced by the methyl group on the quinone and the other functional groups were used for further elaboration. 

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