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Alkaloids from Buxus sempervirens. I. Isolation and characteristics

J. Tomko, Z. Votický, V. Paulík, A. Vassová, and O. Bauerová

Institute of Chemistry, Department of Alkaloids, Slovak Academy of Sciences, Bratislava

Abstract: From the exts. of dried ground leaves of B. sempervirens, by thin-layer chromatography on Al₂O₃ and ir spectrometry, 8 alkaloids, 7 unknown, bebuxine, buxpiine, buxtauine, buxomegine, buxalphine, buxdeltine, and buxetine, and 1 known as alkaloid A or cyclobuxine, C₂₅H₂₄N₂O, (described by Schlitter and Fridrich, CA 44, 9455d), were isolated. The mixt. of all alkaloids was sepd. into 3 fractions, O, C, and L. From the mother liquor of fraction O, after the sepn. of alkaloid A, bebuxine, C26H46N2O, (402.64), m.p. 212-14° (C₆H₆-EtOH), [α]27D +47 ± 3° (c 0.5520, CHCl₃), [α]27D +35 ± 2° (c 0.504, EtOH) was crystd. Bebuxine shows ir spectra max. at 1458 cm^-1 (cyclopropane ring), at 1200 and 1378 cm^-1 (geminal dimethyl), at 3310 cm^-1 (NH), at 3632 cm^-1 and 1038 cm^-1 (OH). By methylation, dimethylbebuxine, C₂₈H₅₀N₂O, m.p. 220-2°, [α]21D + 45 ± 3° (c 0.4120 CHCl₃) and by the acetylation, N,N', O-triacetylbebuxine, C₃₂H₅₂N₂O₄, m.p. 230-5° (ether), [α]27D -57 ± 3° (c 0.8818, CHCl₃) were prepd. From fraction C, buxtauine, buxpiine, and buxomegine were crystd. Buxtauine, C₂₄H₃₇NO2, m. 172-8° (Me₂CO), [α]23.5D +154 ± 3° (c 0.768, CHCl₃), [α]23D +157 ± 2° (c 0.237, EtOH). By hydrogenation, dihydrobuxtauine, m. p. 169-72° (Me₂CO), [α]23.5D +91 ± 3° (c 0.71, CHCl₃) was prepd. Buxtauine shows a max. in the uv region at 203 mμ, indicating a double bond in the positions Δ4 and Δ5 and another exocyclic double bond. The ir spectra show absortions at 1456 cm^-1 (cyclopropane ring), at 1699 cm^-1 (CO), at 837 and 1630 cm^-1 (double bond), and at 1037 and 3595 cm^-1 (OH). Buxpiine, C₂₅H₃₉NO₂, m.p. 173° (ether), [α]21D + 158 ± 3 (c 0.173, CHCl₃) shows ir spectrum max. at 1710 cm^-1 (CO). Buxomegine, C₂₃H₃₉NO, m.p. 172-3° (EtOH-Me₂CO 1:1), [α]26D -40 ± 3° (c 0.726, CHCl₃) has 1 double bond, a tertiary-bonded N atom, and a secondary OH group. It is pptd. by digitonin, which indicates that the OH group is in position 3. The ir spectrum max. at 1065 cm.^-1 gives evidence for Δ5-3β-hydroxy grouping. From the fraction L, buxalphine, buxdeltine, and buxetine were crystd. Buxalphine, C₃₃H₄₈N₂O₂ (mol. wt., 504.73), m.p. 202-5° (ether), [α]24D +56 ± 3° (c 0.872, CHCl₃), [α]26D +61 ± 2° (c 0.90, EtOH) shows a max. of the uv spectra at 235 mμ, indicating a conjugated exocyclic double bond and an ir spectrum with a max. at 1710 cm^-1, indicating CO, and at 1658 cm^-1, indicating NCO groups. By the redn. of buxalphine with LiAlH₄ or NaBH₄, dihydrobuxalphine (buxalphol), C₃₃H₅₀N₂O₂ is formed. It has m.p. 244-9°, [α]21D +81 ± 3° (c 0.26, CHCl₃), [α]23D + 86 ± 2° (c 0.25°, EtOH) and a characteristic ir spectrum max. at 3632 cm^-1 and 1027 cm^-1, indicating OH and at 1658 cm^-1, indicating NCO groups. By catalytic hydrogenation of buxalphine, octahydrobuxalphine (hexahydrobuxalphol), C₃₃H₅₆N₂O₂, m. p. 152-5° (ether), [α]21D +49 ± 3° (c 0.78, CHCl₃), [α]22D +57 ± 2° (c 0.704, EtOH) was prepd. Buxdeltine, C₃₂H₄₄N₂O₃, has a m.p. 275° (ether-MeCO₂), [α]23D +79 ± 3% (c 0.4861, EtOH). Buxetine, C₃₂H₅₀N₂O₃, has a m.p. 263-5°, [α]27D -30 ± 3° (c 0.816, CHCl₃).

Full paper in Portable Document Format: 1810a721.pdf (in Slovak)

Chemical Papers 18 (10) 721–731 (1964)