THE CODEIMETHINES AND THEIR DERIVATIVES

The quaternary salts of codeine and its isomers can be degraded to unsaturated bases to which the general term methylmorphimethine has hitherto been applied, but here the less cumbersome and more systematic term codeimethine [1] will be used, the term methylmorphimethine being reserved for the derivatives obtained from nuclear methylated morphines. The term dihydromethine will be applied to bases in which the double bond introduced by degradation has been saturated. In this way a convenient and unambiguous system of nomenclature is available. 

The reaction between silver oxide and the quaternary salts of morphine and codeine was first investigated, inconclusively, by How [2]. Grimaux, by heating codeine [i] methiodide with silver oxide or potassium hydroxide, obtained a-codeimethine [n] dionin methine likewise could be prepared from dionin (ethyl morphine) methiodide [3-4]. The reaction presumably proceeds by elimination of water from the methohydroxide, and Hesse found that evaporation of codeine methohydroxide solutions over concentrated sulphuric acid affords a-codeimethine [5]. 

Morphine methiodide [m] cannot be induced to degrade in this way owing to formation of the phenol betaine [iv], from which water cannot be eliminated [6]. 

Isocodeine can be degraded to y-codeimethine, the C-6 epimer of a-oodeimethine [15], and like the latter this undergoes isomerization in hot alcoholic alkali, S-codeimethine, epimeric with the /3-isomer, being formed [16]. -Codeine [xm] can be degraded to e-codeimethine [xiv] 

117-18], the epimer of which, -codeimethine, is obtained by the degradation of allo-i/i-oodeine [19], The last two methines cannot be 

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