Alkaloids: Chemistry and Pharmacology, Volume 14 by R.H.F Manske, H.L. Holmes

By R.H.F Manske, H.L. Holmes

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23 STEROID ALKALOIDS 3. 2" in ethanol) was isolated from the green part of Veratrum Zobelianum (69). The mass spectrum of veralozidine exhibited a fragmentation pattern indicative of a 22,26-epiminocholestane skeleton. The UV spectrum of this alkaloid showed a maximum attributable to the C-N double bond. Veralozidine displayed I R absorption due to a hydroxy, a 3phydroxy-5-ene, and a C-N group. The PMR spectrum of veralozidine showed protons associated with the C-18, C-19, C-21, and C-27 methyl groups and a C-6 vinyl proton.

Lobelianum (77) which is above the ground. By catalytic hydrogenation the alkaloid afforded, in ethanol, a dihydro derivative (135);in acetic acid, tetrahydroveracintine (136). The amorphous N,O-diacetyl derivative (137)was isolated in the reaction of veracintine with acetic anhydride in pyridine. The bands in the IR spectrum of 137 showed the amido group and the presence of a double bond. The absorption in the UV I l l spectrum also confirmed the CH3CON-C=Cgrouping in the structure of 137. Biogenetic considerations led to the proposed attachment of the pyrroline ring to C-17.

Cyclovirobuxine-C and Cyclovirobuxeine-C. Cyclovirobuxine-C (165) and cyclovirobuxeine-C (166) were obtained by a countercurrent distribution of the alkaloid mixture prepared by extracting the leaves of Buxus malayana (87). Cyclovirobuxine-C was not obtajn\:d pure because it crystallized with cyclovirobuxeine-C as shown in its PMR spectrum. To get a single product the mixture of 165 and 166 was hydrogenated over platinum catalyst and identified by spectral methods. The proposed structural formula of N-acetylated cyclovirobuxineC (167) was verified by comparison with the synthetically prepared product.

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