A shorter route to the synthesis of (+)-junenol isojunenol, and their coumarate esters from (−)-santonin

Stereoselective Synthesis of Xylodonin A and 22-Hydroxyxylodonin A and Discovery of Analogues with Cytotoxic Activity

The first and stereoselective synthesis of xylodonin A and 22-hydroxyxylodonin A, two drimane-type sesquiterpenoid natural products, was developed from the readily available (+)-sclareolide. This route features an allylic oxidation and acid-promoted dehydration for construction of the key intermediate 6-hydroxyisodrimenin. Representative analogues were synthesized, and their previously unknown bioactivities were revealed after biological evaluation. The analogue 19a exhibited cytotoxic activity against liver cancer HepG2 cells (IC50: 8.8 vs 5.9 μM) that was comparable to that of the clinical anticancer drug etoposide with lower toxicity to normal liver HL7702 cells (IC50 > 100 μM).

First synthesis of (±)-halichonadins A-D

Described herein is the first total synthesis of a marine isocyanide terpene, (±)-halichonadin C. Our synthetic strategy features nitrile-to-isocyanide interconversion utilizing hypervalent iodine-promoted Hofmann rearrangement. This approach led to successful construction of an isocyanide group at the stereochemically encumbered C-6 position in (±)-halichonadin C. Furthermore, in accord with a scenario we propose for the biosynthesis of halichonadins A-D, (±)-halichonadin C was transformed to halichonadins A and B via the missing link intermediate, halichonadin isocyanate.

A reliable validated high-performance liquid chromatography-photodiode array detection method for quantification of terpenes in Copaifera pubiflora, Copaifera trapezifolia, and Copaifera langsdorffii oleoresins

The Copaifera oleoresins are widely used in folk medicine to treat various diseases. The goal of this study was to develop a validated reverse-phase high-performance liquid chromatography method with photodiode array detection (RP-HPLC-PDA) to quantify eight terpenes: ent-hardwickiic acid, ent-copalic acid, ent-7α-acetoxy hardwickiic acid, ent-16-hydroxy-3,13-clerodadiene-15,18-dioic acid, ent-5,13-labdadiene-15-oic acid, junenol, ent-kaurenoic acid, and 13E-ent-labda-7,13-dien-15-oic acid in the oleoresins of Copaifera pubiflora L. (OCP), Copaifera trapezifolia L. (OCT) and Copaifera langsdorffii L. (OCL). The linearity of the method was confirmed in the range of 20.00-500 µg.mL-1 (r2 > 0.999). The limit of quantification was between 1,05 and 16.89 µg.mL-1. Precision and accuracy ranges were found to be %RSD <0.2 and 96% to 110%, respectively. Based on the obtained results, the developed analytical method is rapid, precise, accurate, and sensitive for quantifying these terpenes in Copaifera's oleoresins.

Total synthesis of racemic laurenditerpenol, an HIF-1 inhibitor

The convergent total synthesis of the HIF-1 inhibitor laurenditerpenol 1 and its diastereomer 1' is reported. The key step involves the Julia-Kocienski olefination-reduction process between the sulfone 55 and the aldehyde 54. The unusual trimethylated oxanorbornane sulfone 55 was successfully synthesized from the known exo Diels-Alder adduct 24 of 2,5-dimethylfuran 7 and maleic anhydride 23 in 8 steps. The aldehyde 54 was prepared by ring-opening and elaboration of lactone 41. In addition, four analogues of 1 were also successfully synthesized for biological testing.

Total synthesis of eudesmane terpenes by site-selective C-H oxidations

From menthol to cholesterol to Taxol, terpenes are a ubiquitous group of molecules (over 55,000 members isolated so far) that have long provided humans with flavours, fragrances, hormones, medicines and even commercial products such as rubber. Although they possess a seemingly endless variety of architectural complexities, the biosynthesis of terpenes often occurs in a unified fashion as a 'two-phase' process. In the first phase (the cyclase phase), simple linear hydrocarbon phosphate building blocks are stitched together by means of 'prenyl coupling', followed by enzymatically controlled molecular cyclizations and rearrangements. In the second phase (the oxidase phase), oxidation of alkenes and carbon-hydrogen bonds results in a large array of structural diversity. Although organic chemists have made great progress in developing the logic needed for the cyclase phase of terpene synthesis, particularly in the area of polyene cyclizations, much remains to be learned if the oxidase phase is to be mimicked in the laboratory. Here we show how the logic of terpene biosynthesis has inspired the highly efficient and stereocontrolled syntheses of five oxidized members of the eudesmane family of terpenes in a modicum of steps by a series of simple carbocycle-forming reactions followed by multiple site-selective inter- and intramolecular carbon-hydrogen oxidations. This work establishes an intellectual framework in which to conceive the laboratory synthesis of other complex terpenes using a 'two-phase' approach.

Eudesmane sesquiterpenoids from the Asteraceae family

This review covers the structures and biological activities of eudesmane-type sesquiterpenoids from the plants of the Asteraceae family. Biosynthetic studies or chemical syntheses leading to the revision of structures or stereochemistries have also been included, and 593 references are cited.

New eudesmane derivatives from Melampodium camphoratum from the Suriname rainforest

Bioassay-guided fractionation of an EtOAc extract of the leaves of Melampodium camphoratum using an assay for inhibitors of the degradation of hemin resulted in the isolation of six new eudesmane sesquiterpenes (1-6) and the known 6-epi-beta-verbesinol coumarate (7). The structures of compounds 1-6 were established as 6alpha-(4'-O-methyl-7'E-coumaryloxy)eudesm-4(14)-ene (1), 6alpha-({4'-O-stearyl}-7'E-coumaryloxy)eudesm-4(14)-ene (2), 6alpha-({4'-O-palmityl}-7'E-coumaryloxy)eudesm-4(14)-ene (3), 6alpha-({4'-O-[9' 'Z-hexadecenoyl]}-7'E-coumaryloxy)eudesm-4(14)-ene (4), 6alpha-(7'Z-coumaryloxy)eudesm-4(14)-ene (5), and 6alpha-({4'-acetoxy}-7'Z-coumaryloxy)eudesm-4(14)-ene (6). Compounds 1-4 showed weak activity in the hemin degradation assay, while compounds 5-7 were inactive.

Synthesis of sesquiterpene derivatives as potential antitumor agents; elemane derivatives

Derivatives of elema-1,3-diene were synthesized in several steps as polar analogs of beta-elemene, antitumor agent under clinical phase. The lactone ring of compound 1 was opened by LiAlH4 to give diol 2 which was selectively protected by TBDPSCl. After acetylation of the secondary alcohol, the acetylated product was ozonolyzed and reduced to give elemane derivative 4 which was converted to diolefin 8 via selenides subsequent deprotection by tetrabutylammonium fluoride gave two compounds 9, 10.