Synthesis of bioactive sesterterpenolides from ent-halimic acid. 15-epi-ent-Cladocoran A and B

The Kornblum DeLaMare rearrangement in natural product synthesis: 25 years of innovation

Covering: 1998 up to the end of 2023Since its initial disclosure in 1951, the Kornblum DeLaMare rearrangement has proved an important synthetic transformation and has been widely adopted as a biomimetic step in natural product synthesis. Utilising the base catalysed decomposition of alkyl peroxides to yield a ketone and alcohol has found use in many syntheses as well as a key strategic step, including the unmasking of furans, as a biomimetic synthetic tool, and the use of the rearrangement to install oxygen enantioselectively. Since ca. 1998, its impact as a synthetic transformation has grown significantly, especially given the frequency of use in natural product syntheses, therefore this 25 year time period will be the focus of the review.

Halimanes and cancer: ent-halimic acid as a starting material for the synthesis of antitumor drugs

The development of new anti-cancer agents is an urgent necessity nowadays, as it is one of the major causes of mortality worldwide. Many drugs currently used are derived from natural products. Halimanes are a class of bicyclic diterpenoids present in various plants and microorganisms. Many of them exhibit biological activities such as antitumor, antimicrobial, or anti-inflammatory. Among them, ent-halimic acid is an easily accessible compound, in large quantities, from the ethyl acetate extract of the plant Halimium viscosum, and it has been used as a starting material in a number of bioactive molecules. In this work, we review all the natural halimanes with antitumor and related activities until date as well as the synthesis of antitumor compounds using ent-halimic acid as a starting material.

Roncero A, E. Tobal I, García N, Silva L, Diez D, Mondolis E, Mero A, Morán-Pinzón J, Guerrero EI, Rodilla JM. Antioxidant Activity of New Carvone Derivatives

Carvone is one of the most versatile synthons in organic synthesis. It has been used as starting material for a huge number of organic syntheses of natural products with interesting biological activities. This manuscript communicates the antioxidant activity against superoxide of carvone and several derivatives.

The Methylene-Cycloalkylacetate (MCA) Scaffold in Terpenyl Compounds with Potential Pharmacological Activities

Recently, the methylene-cycloakylacetate (MCA) scaffold has been reported as a potential pharmacophore for neurite outgrowth activity. In this work, natural diterpenes that embed MCA fragments are reviewed, as they are major components of Halimium viscosum: ent-halimic acid, the prototype for these bioactive compounds. Herein, structures, sources, and activities for the natural diterpenes, as well as their synthetic derivatives of interest, are reviewed.

Methylene-Cycloalkylacetate (MCA) Scaffold-Based Compounds as Novel Neurotropic Agents

One of the main symptoms in degenerative diseases is death of neuronal cell followed by the loss of neuronal pathways. In neuronal cultures, neurite outgrowths are cell sprouts capable of transforming into either axons or dendrites, to further form functional neuronal synaptic connections. Such connections have an important role in brain cognition, neuronal plasticity, neuronal survival, and regeneration. Therefore, drugs that stimulate neurite outgrowth may be found beneficial in ameliorating neural degeneration. Here, we establish the existence of a unique family of methylene-cycloalkylacetate-based molecules (MCAs) that interface with neuronal cell properties and operate as acceptable pharmacophores for a novel neurotropic (neurite outgrowth inducing) lead compounds. Using an established PC12 cell bioassay, we investigated the neurotropic effect of methylene-cycloalkylacetate compounds by comparison to NGF, a known neurotropic factor. Micrographs of the cells were collected by using a light microscope camera, and digitized photographs were analyzed for compound-induced neurotropic activity using an NIH image protocol. The results indicate that the alkene element, integrated within the cycloalkylacetate core, is indispensable for neurotropic activity. The discovered lead compounds need further mechanistic investigation and may be improved toward development of a neurotropic drug.

Halimane diterpenoids: sources, structures, nomenclature and biological activities

Diterpenes with a halimane skeleton constitute a small group of natural products that can be biogenetically considered as being between labdane and clerodane diterpenoids.

Antioxidant Activity of Carvone and Derivatives against Superoxide Ion

Carvone has corroborated its versatility as starting material for building blocks synthesis in organic chemistry, being achieved a new chiral lactone. It has been done a study on the antioxidant activity against superoxide of carvone and a chloro derivative that show the potent activity of the natural product ( R)-carvone, 1.

Synthesis of Bioconjugate Sesterterpenoids with Phospholipids and Polyunsaturated Fatty Acids

A series of sesterterpenoid bioconjugates with phospholipids and polyunsaturated fatty acids (PUFAs) have been synthesized for biological activity testing as antiproliferative agents in several cancer cell lines. Different substitution analogues of the original lipidic ether edelfosine (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine) are obtained varying the sesterterpenoid in position 1 or 2 of the glycerol or a phosphocholine or PUFA unit in position 3. Simple bioconjugates of sesterterpenoids and eicosapentaenoic acid (EPA) have been obtained too. All synthetic derivatives were tested against the human tumour cell lines HeLa (cervix) and MCF-7 (breast). Some compounds showed good IC₅₀ (0.3 and 0.2 μM) values against these cell lines.

Unusual cyclic terpenoids with terminal pendant prenyl moieties: from occurrence to synthesis

The paper reviews the known examples of cyclic terpenoids produced from open chain polyenic precursors by an "unusual" biosynthetic pathway, involving selective electrophilic attack on an internal double bond followed by cyclization. The resulting compounds possess cyclic backbones with pendant terminal prenyl groups. Synthetic approaches applied for the synthesis of such specifically functionalized compounds are also discussed, as well as biological activity of reported representatives.

Sesquiterpenyl indoles

The natural product sesquiterpenyl indoles are structural hybrids from farnesyl pyrophosphate and tryptophan or its precursors, often with unusual and complex structural features, many of them with interesting biological activities. In this review the compounds of this class known until now are classified, a biosynthetic approach of each group is proposed and a review of the synthesis or synthetic approaches is communicated.

Synthesis of an ent-halimanolide from ent-halimic acid

An efficient synthesis of ent-halimanolide 2 (15,16-epoxy-12-oxo-ent-halima-5(10),13(16),14-trien-18,2β-olide), from ent-halimic acid has been achieved, corroborating the structure of the natural compound and establishing its absolute configuration.

Coupling of alkenes and alkynes: synthesis of the C1-C11 And C18-C28 fragments of miyakolide

A transition metal-mediated, atom-economical approach toward the crucial A and D rings of miyakolide is described. A Pd-catalyzed alkyne-alkyne coupling/6- endo- dig cyclization is employed to assemble the A ring fragment. The key D ring pyran is constructed utilizing an Ru-catalyzed alkene-alkyne coupling followed by a Pd-catalyzed allylic alkylation to establish the all-cis stereochemistry.

Base-Assisted Regio- and Diastereoselective Conversion of Functionalized Furans to Butenolides Using Singlet Oxygen

A facile synthesis of beta-functionalized gamma-hydroxybutenolides was achieved using a Baylis-Hillman reaction followed by singlet oxygen oxidation. The conversion from 3-furfural was regio- and diastereoselective. [reaction: see text].

Synthetic studies towards the ent-labdane diterpenoids: rearrangement of ent-halimanes

For the first time ent-labdanes have been synthetised starting from ent-halimic acid, following a route that is the reverse of the biosynthetic one leading to the former compounds.

Synthesis of Three Marine Natural Sesterterpenolides from Methyl Isoanticopalate. First Enantioselective Synthesis of Luffolide

[Reaction: see text]. The synthesis of three marine sponge metabolites, luffolide (4), 5, and 6, are described for the first time, establishing the absolute configuration of these compounds. The key intermediate, aldehyde 17, was obtained from methyl isoanticopalate, 11. The addition of 3-furyllithium to 17 and subsequent photochemical oxidation give the gamma-hydroxybutenolide 5 and its epimer at C-16. Sesterterpenolide 6 is obtained by dehydration of 5. From the key aldehyde 17, luffolide (4) was obtained in six steps.

Marine natural products

This review covers the literature published in 2003 for marine natural products, with 619 citations (413 for the period January to December 2003) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (656 for 2003), together with their relevant biological activities, source organisms and country or origin. Biosynthetic studies or syntheses that lead to the revision of structures or stereochemistries have been included (78), including any first total syntheses of a marine natural product.