Structure of the Triterpenes

THE tetracyclic triterpene alcohol basseol, which readily cyclizes to give β-amyrenol1, which in its turn is related to erythrodiol, gypsogenin and hederagenin2, on dehydrogenation with selenium gives as major product a phenanthrene homologue, m.p. 125° (Found: C, 92.7 ; H, 7.2. C17H16 requires C, 92.7 ; H, 7.3; C18H18 requires C, 92.25 ; H, 7.75 per cent), characterized as its picrate, m.p. 165° (Found: C, 61.7 ; 61.8 ; H, 4.2, 4.3 ; N, 9.3. C23H19O7N3 requires C, 61.45 ; H, 4.3 ; N, 9.35 ; C24H21O7N3 requires C, 62.2 ; H, 4.6 ; N, 9.1 per cent). It is apparently identical with the hydrocarbon "C18H18" obtained by Ruzicka, Hosli and Ehmann3from hederagenin. Our analyses favour a trimethyl-rather than a tetramethyl-phenanthrene formulation, but the latter cannot be excluded. The hydrocarbon gives a marked depression in melting point on admixture with 1: 6: 7-trimethylphenanthrene, and it is not identical with 1: 2: 8- or any other known trimethylphenanthrene. The formation of a tri- or (tetra-) methylphenanthrene shows that basseol has one of the partial struct vires I and II. The structure (III) suggested for basseol by Ruzicka and Sehellenberg2 cannot be correct, as this would require the formation of 1: 6-dimethylphenanthrene on dehydrogenation.