Codeine dihydromethine

Codeine dihydromethine [xn] has now been prepared by the sodium-ammonia reduction of codeine methiodide, together with dihydrodesoxy-codeine-C dihydromethine [xiii]. Both [xii] and [xni] result from the sodium and liquid ammonia reduction of a-codeimethine [xiv] [2] (cf. p. 106). The sodium and liquid ammonia reduction of dihydrocodeine methiodide affords a-tetrahydrocodeimethine, and the reduction of /3-codeimethine [xv] yields neopine dihydromethine [xvi]. When the methiodide of the latter is heated with sodium cyciohexyloxide in cyciohexanol a mixture of methyl-morphenol [xvn] and (-f-)-6-hydroxy-3-methoxy-5 6 7 8 9 10-hexahydro-phenanthrylene-4 5-oxide [xviii] is obtained. The latter structure is assigned to the product on account of the close resemblance of its ultra-violet absorption spectrum to that of a-codeimethine. This represents a new type of degradation with hydrolytic scission of the side-chain [2]. Metathebainone methine has also been degraded in this way [2]. 

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. 

---