Abstract
As in the case of 3-methoxy-17α-methylestra-1, 3, 5 (10)-trien-17β-ol (IV), the maximum absorption at 372 nm was immediately shown when 3-methoxyestra-1, 3, 5 (10)-trien-17α-ol (V), 3-methoxyestra-1, 3, 5 (10), 16-tetraene (VI), or 3-methoxy-17β-methyl-18-norestra-1, 3, 5 (10), 13-tetraene (VII) was dissolved in 97.2% H2SO4. Colorless leaflets, mp 122-124°, were obtained in 90% yield when IV came into contact with the same acid at room temperature for 20 min. Ultraviolet, mass and nuclear magnetic resonance spectral data indicated this product to be 3-methoxy-17, 17-dimethyl-13ξ, 14ξ-18-norestra-1, 3, 5 (10), 8-tetraene (VIIIb). Similarly, the same reaction of V, VI, or VII gave 3-methoxy-17β-methyl-13ξ, 14ξ-18-norestra-1, 3, 5 (10), 8-tetraene (VIIIa) in 80-90% yields, which also immediately shows maximum absorption at 372 nm in conc. H2SO4 (Chart 2). Formation of the stable carbocation III seemed to be slow in the case of estradiol-3-methyl ether (II). No χ-372 but χ-465 was formed in conc. H2SO4 with estrone methyl ether (I) which is in higher oxidation state than those of II, IV, V, VI, and VII (Fig. 1).
