<Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR spectra of some drimanic sesquiterpenoids

One- and two-dimensional homo- and heteronuclear correlation proton, carbon, proton—proton, and proton—carbon NMR spectra of fifteen drimanic sesquiterpenoids: 11,12-dibromodrima-5,8-dien-7-one, drim-8-en-7-one, 11-hydroxydrim-8-en-7-one, 11,12-dihydroxydrim-8-en-7-one, 11-hydroxy-11,12-epoxydrim-8-en-7-one, 11-hydroxy-11,12-epoxydrim-8-en-7-one, 8,9-epoxydriman-7-one, 8,9-epoxydriman-7-ol, 11,12-diacetoxydrim-8-en-7-ol, drimane-7,8,11-triol, 7,8-isopropylidenedioxydriman-11-al, 9, 11-dihydroxydrim-7-en-6-one, drimane-7,8,9-triol, drimane-7,8,11-triol, and drim-8-ene-7,11,12-triol were studied. The proton and carbon chemical shifts were assigned.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2589–2594, December, 2004.     

Total Synthesis of (±)‐Integrifolin

The total synthesis of (±)‐integrifolin has been achieved for the first time through the stereoselective preparation of the bicyclo[5.3.0]decane skeleton based on the tungsten‐catalyzed cyclization of acyclic trienynes under photoirradiation conditions. Further key transformations of the cyclized product are the Tamao oxidation through cyclic silyl ether, the introduction of two oxygen functionalities by the oxidation of the diene and the construction of three exo‐methylene moieties.     

The synthetic potential of α,α-diallylcyrene

The reaction of cyrene with allyl bromide in THF in the presence of Bu^tOK gave the α,α-diallyl derivative of cyrene in 50% yield. This derivative smoothly undergoes iodo- cyclization on the keto group that is converted into a ketal center to give annulated bis-tetrahydrofuran; intramolecular cationic cyclization in the presence of SnCl₄ or TiCl₄ results in 2-oxabicyclo[3.3.1]nonan-9-ones. The prospects of using these reactions towards the synthesis of trichothecene sesquiterpenoids modified in the central moiety were assessed.     

Four New Eudesmane Sesquiterpenoid Lactones from Chloranthus serratus

Four new eudesmane sesquiterpenoids endowed with an α,β‐unsaturated γ‐lactone five‐membered ring, serralactones A–D ( 1 – 4 , resp.), along with seven known sesquiterpenoids, were isolated from the whole plant Chloranthus serratus. Their structures and relative configurations were established on the basis of extensive spectroscopic analyses.     

Guaiane Sesquiterpenoids Isolated from the Fruits of Torilis japonica and Their Cytotoxic Activity

Two new guaiane sesquiterpenoids, 11‐(acetyloxy)‐1,8‐dihydroxyguai‐4‐en‐3‐one ( 5 ) and (1α,6β)‐1,6‐dihydroxytorilin ( 6 ), were isolated from the fruits of Torilis japonica (Umbelliferae), along with four known sesquiterpenes, torilin ( 1 ), torilolone ( 2 ), (1β)‐1‐hydroxytorilin ( 3 ), and (1α)‐1‐hydroxytorilin ( 4 ). During the phytochemical investigation, daucosterol, friedelin, and epifriedelanol were also isolated from the plant for the first time. The structures of the new sesquiterpenoids 5 and 6 were determined by comprehensive analyses of MS and NMR spectroscopic data. These isolates were evaluated against human breast cancer cells (MCF‐7) and Lewis lung carcinoma (LLC) cells. Compounds 1, 3 , and 4 exhibited cytotoxic activity against the LLC cells with IC₅₀ values of 31.3, 32.5, and 34.0 μg/ml, respectively. However, no significant cytotoxicity was found against the MCF‐7 cells for any of the compounds tested.     

Cytotoxic triquinane-type sesquiterpenoids from the endophytic fungus Cerrena sp. A593

Abstract

The culture broth of Cerrena sp. A593, which was isolated from Pogostemon cablin, showed potent cytotoxicity against several human tumor cell lines. The following chemical study resulted in the isolation of two new triquinane-type sesquiterpenoids, named cerrenins D (1) and E (2), along with two known compounds plerocybellone A (3) and chloriolin B (4). Their structures were fully assigned with the aid of extensive spectroscopic analysis (¹H and ¹³C NMR, HSQC, HMBC, ¹H-¹H COSY, HRESIMS, and IR) and data from the literature. Moreover, cytotoxic activity in vitro of compounds 1–4 were evaluated against SF-268, MCF-7, NCI-H460, and HepG-2 tumor cell lines. The new compound 1 exhibited weak growth inhibitory activity against all the four tumor cell lines with IC₅₀ values of 41.01, 14.43, 29.67, 44.32?μM.     

Enantioselective synthesis of the bicyclo[4.3.0]nonane ring system of the pinguisane-type sesquiterpenoids via a Brønsted acid promoted transannular enol alkylation

The bicyclo[4.3.0]nonane ring system of the pinguisane-type sesquiterpenoid natural products, including the vicinal quaternary stereocentres, has been synthesised as a single enantiomer via a novel Brønsted acid promoted transannular alkylation of an enol with an unactivated alkene.     

A novel synthesis of guaiane sesquiterpenoids based ontrans-3-isoprenyl-2-(2-methoxycarbonylethyl)cyclopentanone

Synthesis of six guaiane sesquiterpenoids was performed starting from the title cyclopentanone. The structures of the sesquiterpenoids were confirmed by spectral methods. X-ray analysis of the key hydroazulene precursor was carried out.Deceased Nov. 1, 1992.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 126–131, January, 1993.     

倍半萜EnglerinA及其类似物的合成

2008年从东非大戟科属植物Phyllanthus engleri 中分离的吉玛烷型倍半萜(-)-englerin A对6种肾脏癌细胞展示了非常好的抑制活性(GI₅₀:1-87nm),甚至比紫杉醇的抗癌活性高1-2个数量级。这类倍半萜因其结构特点和显著的抗癌活性引起了有机化学界的广泛关注, 短短几年之内,就有多条全合成路线先后被报道。本文主要综述了(-)-englerin A及其类似物的合成进展,按照各个研究小组运用的关键策略加以分类,来阐述他们各自的合成特点。     

The new synthesis of sesquiterpenoids 10-bromo-α-chamigrene

The new synthesis of 10-bromo-α-chamigrene was achieved as follows;6-methyl-5-heptene-2-one was transformed into corresponding thioacetals,and then successively treated with Cp_2Ti(P(OEt)_3)_2.The intermediate reacted with mono-ketal of cyclohexane-1,4-dione,and gave the carbonyl coupling product.It was then transformed into the key intermediateγ-bisabolene via deketalization,Grignard reaction,dehydration and then furnished the target molecule by polyene cyclization,with total yield 2%. All structures we...