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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]

Three new C19-diterpenoid alkaloids, umbrosumines A-C (1-3), and 11 known compounds (4-14) were isolated from the roots of Delphinium umbrosum. Their structures were elucidated on the basis of the spectroscopic data interpretation. [ABSTRACT FROM AUTHOR]

In the title study, the synthesis of the vital intermediate C-nor-aconanone (3) from 4 was completed through 11 steps, mainly including semipinacol rearrangement, formation of the imines by the treatment of 10 or 20 with NBS, the cleavage of N-C(19) bonds in 11 or 21 by treatment with m-CPBA and subsequently with LTA, as well as the rupture of the N-C(17) bonds in 22 by a modified Nef reaction (NaH/t-BuOH → KMnO4/H2O). One-pot procedure was successfully developed starting from 11 or 21 to afford the N,19-seco-C-nor product 15 or 22, respectively, in reasonably good yields. [ABSTRACT FROM AUTHOR]

Two new C 19 -diterpenoid alkaloids, kongboentine A ( 1 ) and kongboentine B ( 3 ), were isolated from the roots of Aconitum kongboense Lauener and their structures were elucidated by spectral data. [ABSTRACT FROM AUTHOR]

Following the report on the synthesis of the 7,17-seco compounds [Wang, F.P., Yang, J.S., Chen, Q.H., Yu, L. and Li, B.G. (2000), Chem. Pharm. Bull. 48, 1912-1916], further studies on the reaction optimization for cleavage of the C(7),C(17) bond led to the 7,17-seco norditerpenoid alkaloids (e.g. 4, 9) in nearly 90% yield. [ABSTRACT FROM AUTHOR]

The O-acyl group at C-1 of two C19-diterpenoid alkaloids 2 and 5 was transferred to the secondary amine nitrogen to form amides 3 and 6 in the basic condition. This kind of O-to-N intramolecular acyl migration could be caused by the near distance between the nucleophilic nitrogen atom and the carbonyl group of the ester at C-1 in the C19-diterpenoid alkaloids, which is consistent with the conformation of rings A and E in the C19-diterpenoid alkaloids. [ABSTRACT FROM AUTHOR]

The first biomimetic conversion from the aconitine-type C19-diterpenoid alkaloids to the corresponding alkaloids of lactone-type C19-diterpenoid alkaloid has been achieved. Chasmanine was used as starting material with Baeyer–Villiger oxidation as a key reaction. It was also observed that the oxygenated group at C-16 did not change the relative migration tendencies of C-13 and C-9 during the oxidation. Meantime, a novel D-ring fragmented compound was obtained during the course of the present investigation. The plausible mechanism of the formation of this compound was also proposed. [ABSTRACT FROM AUTHOR]

Treatment of some C19-diterpenoid alkaloids (3, 6, 10 and 12) with anhydrous DMSO at 100-170°C for 3-7 h led to the formation of the corresponding imines (4, 7/8, 11, 13/14) in 65-83% yield, respectively. This is a new simpler formation of the imines of the C19-diterpenoid alkaloids. [ABSTRACT FROM AUTHOR]

A new franchetine-type (leueandine 1 ) and two new lycoctonine-type [potanisines F ( 3 ) and G ( 5 )] C 19 -diterpenoid alkaloids have been isolated from the roots of Aconitum hemsleyanum var. leueanthus and Delphinium potaninii , respectively, and their structures were established on the basis of spectral data. [ABSTRACT FROM AUTHOR]

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]

A series of new bisbenzylisoquinoline alkaloids was partially synthesized from tetrandrine and fangchinoline and evaluated for their ability to reverse P-glycoprotein-mediated multidrug resistance (MDR) in cancer cells. All the test compounds increased the intracellular accumulation rate of rhodamine 123 in MDR cells (Bel7402 and HCT8), and most exhibited more potent MDR-reversing activity relative to the reference compound verapamil. Compounds 8, 10, 13, and 14 enhanced intracellular accumulation of doxorubicin in Bel7402 and HCT8 cells. [ABSTRACT FROM AUTHOR]