C20-diterpenoid alkaloids

Two New C20-Diterpenoid Alkaloids from Delphinium anthriscifolium var. savatieri

Further phytochemical investigation of the whole herb of Delphinium anthriscifolium var. savatieri resulted in the isolation of two new C20-diterpenoid alkaloids, anthriscifolmines I (1) and J (2). The structures of the two new alkaloids were elucidated on the basis of spectral data, including 2D NMR and HRESIMS.

Chemical constituents from Delphinium chrysotrichum and their biological activity

A new diterpene alkaloid named delphatisine C (1) has been isolated from aerial parts of Delphinium chrysotrichum along with three known norditerpenoid alkaloids delpheline (2), delbrunine (3), and delectinine (4). Their structures were characterized on the basis of their spectral data. All of them were determined by SRB assay for their cytotoxicity, and compound (1) showed significant cytotoxic activities (IC(50)=2.36 μmol/L) against the A549 cell line.

Structure-analgesic activity relationship studies on the C(18)- and C(19)-diterpenoid alkaloids

For evaluation of C(18)- and C(19)-diterpenoid alkaloids as analgesics, three C(19)-diterpenoid alkaloids were isolated from the roots of Aconitum hemsleyanum var. circinatum and A. transsecutum; and twenty-five semisynthetic C(18)- or C(19)-diterpenoid alkaloids were prepared from lappaconitine, crassicauline A or yunaconitine. In a mice acetic acid-induced abdominal constriction assay, four crassicauline A analogs and three yunaconitine analogs exhibited good analgesic activities with 77.8-94.1% inhibition range in 0.1-10 mg/kg subcutaneous (s.c.) dose range at the point of 20 min after drug administration. Among them, 8-O-deacetyl-8-O-ethylcrassicauline A (ED(50)=0.0972 mg/kg) and 8-O-ethylyunaconitine (ED(50)=0.0591 mg/kg) were the most potent analgesics relative to the reference drugs lappaconitine (ED(50)=3.50 mg/kg) and crassicauline A (ED(50)=0.0480 mg/kg). Analgesic activity data of these C(18)- and C(19)-diterpenoid alkaloids indicate that a tertiary amine in ring A, an acetoxyl or an ethoxyl group at C-8, an aromatic ester at C-14, and the saturation state of the ring D are important structural features necessary to the analgesic activity of the C(19)-diterpenoid alkaloids.

A new hetisine-type diterpenoid alkaloid from Aconitum coreanum

A new hetisine-type alkaloid, named as guan-fu base A1 (1), and five known alkaloids including guan-fu base G (2), guan-fu base Y (3), guan-fu base Z (4), guan-fu base Q (5) and coldephnine (6) were isolated from the roots of Aconitum coreanum. The structure of 1 was established by spectral methods, especially 2D NMR techniques.

Diterpenoid Alkaloids from Delphinium majus

From the whole herbs of Delphinium majus, three new C(19)-diterpenoid alkaloids, majusines A-C (1-3), and six new C(20)-diterpenoid alkaloids, majusimines A-D (4-7) and majusidine A and B (8 and 9), have been isolated, together with 15 known compounds. The structures of compounds 1-9 were elucidated by spectroscopic data interpretation.

An effective O-demethylation of some C19-diterpenoid alkaloids with HBr-glacial acetic acid

The aconitine-type alkaloids talatisamine (1), 8,14-diacetyltalatisamine (11), and compound 3, the lycoctonine-type alkaloid deltaline (5), and the 7,17-seco C(19)-diterpenoid alkaloids 7 and 9 were treated with HBr-glacial acetic acid to give useful O-demethylated derivatives 2, 2, 4, 6, 8, and 10 respectively in good to high yields (49-90%).

Bisnorditerpene, norditerpene, and lipo-alkaloids from Aconitum toxicum

From the roots of Aconitum toxicum, acotoxicine (1), a new bisnorditerpene alkaloid, was isolated together with the structurally related delavaconitine, delavaconine, dolaconine, aconosine, and the norditerpene alkaloid neolinine. The structure of compound 1 was elucidated by spectroscopic data interpretation. Further, eight lipo-alkaloids (2-9) were detected in the plant material by LC-APCI-MSn analysis. This is the first report of a C18 bisnorditerpene alkaloid and lipo-alkaloids from A. toxicum.

Asymmetric synthetic access to the hetisine alkaloids: total synthesis of (+)-nominine

A dual cycloaddition strategy for the synthesis of the hetisine alkaloids has been developed, illustrated by a concise asymmetric total synthesis of (+)-nominine (7). The approach relies on an early-stage intramolecular 1,3-dipolar cycloaddition of a 4-oxido-isoquinolinium betaine dipole with an ene-nitrile dipolarophile. Subsequent late-stage pyrrolidine-induced dienamine isomerization/Diels-Alder cascade allows for rapid construction of the carbon--nitrogen polycyclic skeleton within this class of C(20)-diterpenoid alkaloids.

Hetisine-type diterpenoid alkaloids from the Bhutanese medicinal plant Aconitum orochryseum

Investigation of Aconitum orochryseum, a Bhutanese traditional medicine ("gSo-ba Rig-pa") plant locally known as "Bong-kar", resulted in the isolation of three new hetisine-type diterpenoid alkaloids, named orochrine (1), 2-O-acetylorochrine (2), and 2-O-acetyl-7alpha-hydroxyorochrine (3), together with the previously reported alkaloids atisinium chloride (4) and virescenine (5). The structures of the new alkaloids were elucidated by spectroscopic data analysis.

Tricalysiamides A-D, diterpenoid alkaloids from Tricalysia dubia

Four rearranged ent-kaurane diterpenoid alkaloids, tricalysiamides A-D (1-4), having a cafestol-type carbon framework were isolated from the wood of Tricalysia dubia. Their absolute structures were determined on the basis of 2D NMR spectroscopy, X-ray crystallographic analysis, and chemical methods.

New diterpenoid alkaloids from the roots of Delphinium tiantaishanense

Four new diterpenoid alkaloids: tiantaishansine (1), tiantaishannine (2), tiantaishanmine (3), and tiantaishandine (4) have been isolated from the roots of Delphinium tiantaishan. Their structures were elucidated by chemical evidence and spectral analyses, including ESI-MS, HR-EI-MS, 1D- and 2D-NMR.

Three New Diterpenoid Alkaloids from Roots of Aconitum ouvrardianum HAND.-MAZZ

A new C(19)-diterpenoid alkaloid, ouvrardiantine (1) and two new C(20)-diterpenoid alkaloids, ouvrardiandines A (2) and B (3) were isolated from the root of Aconitum ouvrardianum HAND.-MAZZ. The structure of the new alkaloids was established on the basis of spectral data (1D- and 2D-NMR, HR-MS).

Efficient synthetic access to the hetisine C20-diterpenoid alkaloids. A concise synthesis of nominine via oxidoisoquinolinium-1,3-dipolar and dienamine-Diels-Alder cycloadditions

A concise synthetic approach to the hetisine C20-diterpenoid alkaloids is reported. The total synthesis of (+/-)-nominine was accomplished in a 15-step sequence employing a dual cycloaddition strategy. Key features of the synthesis include a reversible intramolecular 4-oxidoisoquinolinium betaine dipolar cycloaddition in conjunction with a pyrrolidine-induced dienamine isomerization/Diels-Alder cascade.

Enantioselective approach to the hetisine alkaloids. Synthesis of the 3-methyl-1-aza-tricyclo[5.2.1.0(3,8)]decane core via intramolecular dipolar cycloaddition

[structure: see text]. An efficient, enantioselective approach to the hetisine class of the C(20)-diterpenoid alkaloids is described. The strategy involves an intramolecular oxidopyridinium dipolar cycloaddition as the key transformation, in which simultaneous formation of the C5-C6 and C10-C20 bonds in the 3-methyl-1-aza-tricyclo[5.2.1.0(3,8)]decane core of the hetisine alkaloids is effected.

C20-diterpenoid alkaloids from Delphinium trifoliolatum

Three new C20-diterpenoid alkaloids, trifoliolasines D-F (1-3), were isolated from the aerial parts of Delphinium trifoliolatum, and their structures were determined by the interpretation of spectroscopic data and by the single-crystal X-ray crystallographic analysis of 1.

mCPBA Oxidation of Acetyllycoctonine and Its New Products

Treatment of a lycoctonine-type alkaloid acetyllycoctonine (4) with mCPBA at room temperature led to acetyllycoctonine N-oxide (5) as the major product together with other interesting compounds 6-12 as the minor products, which were derived from oxidation involving the nitrogen atom and Cope elimination as well as Polonovski-like fragmentation. All of those new compounds (5-12) were fully characterized.