Degradation with loss side chains

More direct methods for the degradation of the side-chain of cyclolaudenol have been published/ It has been shown, using the squalene 2,3-oxide (38) with a chiral methyl group, that the 1,3-proton loss in the formation of the cyclopropane ring of cycloartenol occurs with retention of configuration at the C-10 methyl group/ ... 

Side chain degradation is also a common problem, and those substrates with long diains at C-17 (e.g. cholesterol) are difficult to hydroxylate without loss or truncation of the hydrocarbon chain. 

Alkaline degradation of codeine methiodide affords a-codeimethine [xxi] [185, 285], which can be isomerized by alcoholic alkali to /3-codeimethine [xxn] [187, 286-7], also obtainable by the degradation of neopine [xm] methiodide [271]. The degradation of codeine ethiodide follows a similar course [288]. These bases suffer dehydration and loss of the basic side-chain when heated with acetic anhydride and sodium acetate (when acetylmethylmorphol [xxm] is formed [187, 289-90]), and when subjected to further Hofmann degradation (which leads to methylmorphenol [xxiv] [290-2]). The resulting aromatic phenan-threne derivatives are of considerable importance in the elucidation of the basic structure of the morphine alkaloids and are discussed in detail in Chapter XXVII. 

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