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The relative reactivity of three hydroxyl groups in aconitine toward acetylation, chlorination, sulfonylation, and oxidation has been studied in this paper. The reduction of C-3 ketone and C-15 ketone derivatives of aconitine was also investigated. It was found that (1) the relative reactivity of three hydroxyl groups toward acetylation, chlorination, and sulfonylation is 3-OH>13-OH>>15-OH; (2) 3-OH is much more reactive than 15-OH toward oxidation; and (3) reduction of the carbonyl group at C-3 with NaBH4 generated a pair of C-3 epimers, while the reduction products of the carbonyl group at C-15 depend largely on the specific reducing agent and the absolute configuration of 16-OCH3. When the substrate has 16β-OCH3, its carbonyl group at C-15 can be reduced with NaBH4 to yield exclusively the 15α-OH-containing product. Upon replacement of reducing agent NaBH4 with LiAlH4, the C-15 carbonyl group can be reduced to yield a pair of C-15 epimers. On the other hand, when the substrate has 16α-OCH3, C-15 carbonyl group can only be reduced to generate 15α-OH-containing product. [ABSTRACT FROM AUTHOR]

Four novel taxoid analogs were conversionally synthesized from the C19-diterpenoid alkaloid deltaline, and their cytotoxic activities were evaluated against a small panel of cancer cell lines. [ABSTRACT FROM AUTHOR]

The regioselective demethylations of two C19-diterpenoid alkaloids, 2 and 3, have been achieved with HBr-HOAc, trimethylsilyl iodide, or BBr3. It was observed that HBr-HOAc is an optimal demethylating agent for these two C19-diterpenoid alkaloids because it could provide different O-demethylation products by using different reaction temperature and reaction time. Especially, 1-O-methyl group in 2 and 3, one of the most difficult ones to be demethylated, could be removed by the treatment with HBr-HOAc at an elevated temperature and a prolonged reaction time. [ABSTRACT FROM AUTHOR]

The conversional synthesis of taxoids by the BAC sequence from the C19-diterpenoid alkaloids, 14-acetyltalatisamine (1), yunaconitine (12), and 14-acetylchasmanine (19), was designed and explored. Two aconane-type diterpenes 17 and 28, the advanced intermediates for our conversional synthesis, were synthesized. The key steps include the rupture of the C(7)-C(17) bond, the formation of imine, and the denitrogenation. [ABSTRACT FROM AUTHOR]