Indole alkaloids from Kopsia jasminiflora

Seven new indole alkaloids (aspidofractinine type 1–3, kopsine type 5, strychnos type 6, and vincamine type 7, 8) were isolated from Kopsia jasminiflora (Apocynaceae) collected in Thailand. 5-Oxokopsinic acid (4) was isolated from nature for the first time. The structures of the new alkaloids were determined by spectroscopic analyses and chemical transformation of a known alkaloid. 5,6-Secokopsinine (1) possesses a dialdehyde function that is formed by oxidative cleavage of the C-5–C-6 bond of kopsinine (9). New vincamine-type alkaloid 8 showed potent inhibitory activity toward human cancer cell lines (A549, HT29, HCT116).     

Seven New Monoterpenoid Indole Alkaloids from Gelsemium elegans

Seven new indole alkaloids were isolated from the roots of Gelsemium elegans Benth. and their structures were determined by spectroscopic analysis and chemical transformation from known alkaloids. Kounaminal ( 1 ) is a new koumine‐type alkaloid that contains an unusual aminal moiety. Humantenoxenine ( 2 ) and 15‐hydroxyhumantenoxenine ( 3 ) are humantenine‐type alkaloids that contain a novel β‐amino‐α,β‐unsaturated ketone residue. The other four novel alkaloids are two gelsedilam‐related and two gelsenicine‐related alkaloids.     

New procedure to mask the 2,3-pi bond of the indole nucleus and its application to the preparation of potent opioid receptor agonists with a Corynanthe skeleton

Treatment of indole alkaloids with hypervalent iodine in the presence of ethylene glycol provides 2,3-ethylene glycol bridged adducts that could be converted into the original indoles under mild reductive conditions. This procedure, which involves masking of the reactivity of the indole nucleus at the beta-position, was utilized for the modification of the benzene ring of the indoline derivative and was applied to the preparation of potent opioid receptor agonists with the Corynanthe skeleton. [reaction: see text]     

A new pimarane from Mitrephora tomentosa

A new diterpenoid named (-)-8beta-hydroxypimar-15-en-18-oic acid was isolated, along with (-)-kaur-16-en-19-oic acid, 13,14-dihydrooropheic acid and beta-sitosterol, from the bark of Mitrephora tomentosa.     

Ten new fawcettimine-related alkaloids from three species of Lycopodium

Ten new fawcettimine-related alkaloids, i.e., lycopoclavamines, lycoposquarrosamine-A, and other hydroxylated fawcettimine derivatives, were isolated from three species of Lycopodium (Lycopodium clavatum, Lycopodium serratum, and Lycopodium squarrosum). The structures of the new alkaloids were elucidated by spectroscopic methods and chemical correlation.     

Four novel gelsenicine-related oxindole alkaloids from the leaves of Gelsemium elegans benth

[reaction: see text] New types of four gelsenicine-related oxindole alkaloids were isolated from the leaves of Gelsemium elegans Benth. Gelsedilam (1) and 14-acetoxygelsedilam (2) are the first examples of 18,19-nor-type monoterpenoid indole alkaloids. Gelsefuranidine (3) and gelseiridone (4) have, respectively, an additional furan residue or an iridoid unit on the gelsenicine-related monoterpenoid indole alkaloid.     

New iridoids from Gelsemium species

Four new iridoids structurally related to gelsemide (5) were isolated from two Loganiaceous plants, Gelsemium elegans and G. rankinii. Among them, GEIR-1 (1) has a novel tetracyclic caged structure.     

New humantenine-type indole alkaloids with iridoid unit from Gelsemium species

Two new oxindole alkaloids, rankiniridine (1) and humanteniridine (2), having a nitrogen-carbon linkage between a humantenine-type monoterpenoid indole alkaloid and a monoterpene unit with an iridoid skeleton, were isolated from Gelsemium rankinii and Gelsemium elegans, respectively.