抄録
In the previous paper, the isolation of 24-methylene-cycloarthanol from wheat-germ oil had been reported.
In this paper, a new methylsterol named “gramisterol” having mp 169°C, [α]590+0.5° and mp 152°C, [α]590+28.1° of its acetate and formula C29H48O was isolated by repeating chromatographic separation of the more soluble fraction of the sterols.
Gramisterol was precipitated with digitonin, reacted with the Liebermann-Burchard reagent very rapidly and developed blue color more deeply than Δ7-stenol (Fig. 1), and the spectrum of its color was characteristic (Fig. 2).
The difference between the molecular rotation of gramisteryl-acetate and that of free gramisterol was +126°, and was obiously greater than the molecular rotation difference of any sterol series (in a narrow sense) excluding Δ5, 7-sterols.
Gramisterol showed no absorption maximum of UV spectrum (above 220 mμ), and the IR spectrum (Fig. 3) showed the presences of trisubstituted olefine (6.00μ, 11.87μ, 12.05μ, 12.22μ, 12.45μ), vinylidene (3.253μ, 6.09μ, 11.29μ) and gem-dimethyl (7.33μ) groups.
NMR spectrum of this sterol (Fig. 4) had two signals at τ 9.46 and τ 9.17, which were corresponded to two methyl groups connected with C-13 and C-10 respectively, and any other methyl group connected with tertiary carbon atom was not present. The doublet signals at τ 8.97 and τ 9.08 (J=6.6 cps) (at 40 Mc, τ 8.95 and τ 9.12, J=6.8 cps) seemed to indicate one methyl group connected with C-4. The orientation of the methyl group was presumed as α- or equatorial configuration, because the signal of the methyl group connected with C-10 (no 1, 3 diaxial) was appeared at normal position of τ 9.17. The doublet signals at τ 8.93 and τ 9.04 (J=6.6 cps) (at 40 Mc, τ 8.91 and τ 9.08, J=6.8 cps) would be derived from gem-dimethyl group connected with C-25, owing to vinylidene bond connected to the carbon atom.
From the above results, the structure of gramisterol was presumed as 4α-methyl-Δ7, 24(28)-ergostadien-3β-ol.
