Chemistry 161 



oi an enolonc system in colchiceine and of a corresponding enolone- 

 niethvl-ether system in colchicine. 



Although neither colchicine nor colchiceine reacts with the usual 

 carbonyl reagents, hydrogenation results provide evidence ot the 

 presence oi a carbonyl group in each. Bursian^* found that with a 

 platinum catalyst both compoinids absorbed three moles of hydrogen 

 and that thereby colchicine gave a mono-alcohol while colchiceine gave 

 a diol. In each case therefore a new hydroxylic function has been pro- 

 duced and may well arise from reduction of a carbonyl group by one 

 mole of hydrogen. The absorption of two further moles of hydrogen 

 shows the presence of two olefniic groups, while the presence of yet 

 a third olefinic group, which resists hydrogenation, was indicated by 

 the interaction of liexahydrorolchicine, C^jHyiOoN, with perbenzoic 

 acidic or with monoperphthalic acid (Tarbell et al.^^) to form an 

 oxide, CjoH:„07N. 



Summing up: The evidence suggests that colchicine is the methyl 

 ether of an enolone which contains three additional methoxyl groups, 

 an acetylated primary amino-group. and three non-benzenoid dotd:)le 

 bonds: 



Ci,H, (OMe) 4 (NH.COMe) (:0) (=) 3- 



6.3: The Structural Problem 



The saturated hydrocarbon, Ci.jHoo, which corresponds to this 

 assemblage of groups, fall short of the j)araftin, Ci,;H34, by six hydro- 

 gen molecules each of which in default indicates the presence of either 

 a carbon ring or a benzenoid type of double bond. Four of the miss- 

 ing hydrogen molecules are at cjijce accounted for by the demon- 

 strable presence of a benzenoid ring; the remaining two must there- 

 fore denote two further ring systems. Colchicine is accordingly tri- 

 cyclic and the respective rings, both in the alkaloid and in its 

 degradation products, are designated by the letters A, B, and C. 



6.5-/; Ring A. The presence of the benzenoid ring (A) is shown 

 by the formation of •5:4:5-trimethoxyphthalic acid (I), or its anhy- 

 dride, from colchicine and many of its derivati\'es on oxidation with 

 hot alkaline permanganate (Windaus^''- i") . 



6.5-2; Ri)ig B. The most penetrating insight into the molecular 

 structure of colchicine is obtained through a series of degradation 

 products (Windaus^^' ^^) derived from N-aceiyliodocolchinol. C20H22 

 O5NI. This compound is formed from colchiceine by the action of 

 iodine in the presence of alkali. It is definitely phenolic and is re- 

 duced by zinc and acetic acid to ^i-acetylcocJilnol, C^qH^^O.-.N, which 

 on methylation ailords N-acetylcolchinol methyl ether. The latter still 

 contains the acetylated primary amino-group and may be deaminated 



