Total synthesis of panaxytriol and panaxydiol

The enantioselective total synthesis of the diyne containing natural products panaxytriol and (3S,10R)-panaxydiol from L-tartaric acid is reported. Key steps in the synthesis include the elaboration of a gamma-hydroxy amide derived from tartaric acid to the required alkyne and the formation of the desired diyne unit by a Cadiot-Chodkiewicz coupling. (C) 2011 Elsevier Ltd. All rights reserved.

Transient electric field distribution within the working volume of an NEMP simulator

Nuclear electro-magnetic pulse (NEMP) simulators which are used in the simulation of transient electromagnetic fields due to a high altitude nuclear detonation are generally excited with a double exponential high voltage pulse. This results in a current distribution on the wires of the simulator and hence a transient electric field in the working volume of the simulator where the test object is kept. It is found that for the simulator under study, the current distribution is non-uniform and so is the field distribution along the width of the simulator in the working volume. To make the current distribution uniform, several methods have been suggested and the results of these methods are analyzed and suitable conclusions are arrived at from those results.

Total synthesis of (-)-ent-pachastrissamine (ent-Jaspine B)

The total synthesis of the enantiomer of the tetrahydrofuran containing natural product Jaspine B is reported. The key reactions in the synthesis include formation of the tetrahydrofuran unit by an acid mediated Williamson etherification and a subsequent elaboration with an olefin cross metathesis reaction. (C) 2011 Elsevier Ltd. All rights reserved.

An Enantiospecific Formal Total Synthesis of the 5-8-5 Tricyclic Diterpene ent-Fusicoauritone

An enantiospecific formal total synthesis of the 5-8-5 tricyclic diterpene fusicoauritone has been accomplished, starting from 5-isopropyl-2-methylcyclopent-1-enemethanol [available in three steps from (R)-dihydrolimonene] employing two ring-closing-metathesis reactions for the construction of the eight- and five-membered rings.

Enantiospecific first total synthesis of (6S,7R)-silphiperfolan-6-ol

Enantiospecific first total synthesis of the angular triquinane sesquiterpene (65,7R)-silphiperfolan-6-ol has been accomplished, starting from 2-(3-isopropenyl-2-methylene-1-methylcyclopent-1-yl)acetic acid (readily available from (R)-limonene) employing an efficient, regioselective intramolecular rhodium carbenoid insertion into the CH bond of a tertiary methyl group as the key step. (C) 2012 Elsevier Ltd. All rights reserved.

Enantiospecific total synthesis of 15-hydroxy-5-(methoxymethoxy)crinipellin-9-one

Enantiospecific total synthesis of the crinipellin mentioned in the title was accomplished. In the present synthesis cyclopentane ring in campholenaldehyde was identified as the B-ring, two intramolecular rhodium carbenoid CH insertion reactions were employed for the construction of the A and C rings, and an intramolecular Michael addition reaction was utilized for the construction of the D-ring of crinipellin. (C) 2012 Elsevier Ltd. All rights reserved.

Enantiospecific First Total Synthesis of ent-Allothapsenol

The enantiospecific first total synthesis of the enantiomer of the irregular sesquiterpene from Ligusticumgrayi allothapsenol, starting from the readily available monoterpene (R)-carvone, is described, which confirmed the assumed absolute configuration of the natural product.

The substrate dependent competitive formation of cyclobutanones and cyclopentanones in an intramolecular rhodium carbenoid CH insertion reaction: enantiospecific total synthesis of silphiperfol-6-ene

The enantiospecific total synthesis of silphiperfol-6-ene has been accomplished starting from the readily available monoterpene (R)-limonene, employing a rhodium carbenoid insertion into the CH bond of a tertiary methyl group. A substrate dependent competitive insertion of the rhodium carbenoid in the gamma- and beta-CH bonds to form cyclopentanone and cyclobutanones, respectively, has been described. (C) 2012 Elsevier Ltd. All rights reserved.

Total Synthesis of (+)-Eburnamonine

The enantiospecific total synthesis of vinca alkaloid (+)-eburnamonine is accomplished from L-ethyl lactate. Key feature of the synthesis is the construction of the chiral quaternary center involving a Johnson-Claisen rearrangement and assembly of the pentacyclic core by the Pictet-Spengler reaction and ring-closing metathesis.

Total Synthesis of (+)-Cladospolide A

A stereoselective total synthesis of (+)-cladospolide A from D-ribose is described. Key features of the synthesis include olefin cross metathesis and Yamaguchi lactonization.

Total synthesis of (+)-phomopsolide B

An enantiospecific total synthesis of polyhydroxy delta-pyrone natural product phomopsolide B is accomplished. The main feature of the synthesis is the installation of the required E-olefin by Horner-Emmons-Wordsworth reaction and the formation of the lactone involving Still-Gennari olefination followed by lactonization. (C) 2012 Elsevier Ltd. All rights reserved.

An Approach to seco-Prezizaane Sesquiterpenoids: Enantioselective Total Synthesis of (+)-1S-Minwanenone

A strategy of general applicability toward seco-prezizaane sesquiterpenes, from a chiral, tricyclic synthon, readily available via an enzymatic resolution step from the Diels-Alder adduct of cyclopentadiene and p-benzoquinone, has been devised. Our approach enables harnessing of the stereochemical proclivities of the norbornyl system to install the desired stereochemistry at the key stereogenic centers. Recourse to an interesting stratagem to realign a stereochemical divergence into stereoreconvergence forms the cornerstone of our successful approach. The first total synthesis of (+)-1S-minwanenone, a prototypical member of seco-prezizaane subclass, has been accomplished.

Enantiospecific Total Synthesis of (-)-Bengamide E

Total synthesis of the polyhydroxy caprolactam amide natural product, bengamide E, is accomplished starting from tartaric acid. Key reactions in the synthesis include desymmetrization of the bis(dimethylamide) unit of tartaric acid, Zn(BH4)2-mediated anti-selective reduction, and a HornerWadsworthEmmons olefination.

An Expeditious Enantiospecific Total Synthesis of (-)-Crassalactone C

A concise and expeditious approach for the total synthesis of bioactive styryllactone (-)-crassalactone C is presented from tartaric acid. The main features of the synthesis include the desymmetrization of dimethylamide of tartaric acid and the effective use of cinnamoyl ester as a protecting group as well as a reactant in the ring-closing metathesis reaction.

Enantiospecific total synthesis of indole alkaloids (+)-eburnamonine, (-)-aspidospermidine and (-)-quebrachamine

An enantiospecific total synthesis of indole alkaloids eburnamonine, aspidospermidine and quebrachamine is described from lactic acid. Synthesis of all three alkaloids is accomplished from a single chiral building block. Johnson-Claisen rearrangement of a chiral allyl alcohol is the main feature for the installation of the required quaternary centre.