New prostaglandin (PGF) derivatives from the soft coral Lobophyton depressum

Four PGF derivatives (15S)-PGF_2α-11-acetate methyl ester ($\text{1}$a), the 18-acetoxy derivative of compound $\text{1}$a ($\text{2}$a) as well as their two corresponding free carboxylic acids ($\text{1}$b) & $\text{2}$b) were isolated from a soft-coral and their structure elucidated, mainly on basis of their spectral data.     

Syntheses of (±)-pyrenophorin and (±)-colletallol

Pyrenophorin $\text{1}$ and colletallol $\text{3}$ were synthesized in their racemic forms from the corresponding hydroxycarboxylic acids $\text{9}$ and $\text{14}$ via stereoselective formation of the requisite trans double bonds after macrocyclization.     

Phospholipid studies of marine organisms 9. New brominateddemospongic acids from the phospholipids of two petrosia species

Two Novel long chain fatty acids, (5Z, 9Z)-6-bromo-25-methyl-5,9-hexacosadienoic and (5Z, 9Z)-6-bromo-24-methyl-5,9-hexacosadienoic acids were found in the phospholipids of $\text{Petrosia}$$\text{ficiformis}$ and $\text{P.}$$\text{hebes}$. Their structures were elucidated with the help of CI-EI7MS and a homogeneous hydrogenation catalyst.     

Regioselective intramolecular asymmetric cyclization of symmetrical open chain triketone

The title reactions performed with (S)-α-amino acids or their derivatives as chiral sources were found to regioselectively give enantiomeric pairs of optically active 4-acetyl-3, 4-dimethyl-2-cyclohexenone (R)(+)- and (S)(?)-$\text{4}$), 16–25% e.e., and those of optically active 6-acetyl-3,6-dimethyl-2-cyclohexenone((R)(+)- and (S)(?)-$\text{5}$, 54–59% e.e., from the open chain triketone($\text{3}$).     

A new class of macrocyclic diterpenes from Bertyadimerostigma (euphorbiaceae)

Three diterpene acids, representing a new class of bicyclic diterpenes, have been isolated from $\text{Bertya dimerostigma}$ F. Muell. (Euphorbiaceae). Spectroscopic and X-ray cryatallographic evidence for their structure is presented. A rationale for their origin $\text{via}$ modification of the casbane skeleton is given.     

Synthesis of enantiomerically enriched atrolactic acid and other α-hydroxy acids

The α-anions of 2-substituted 1,3-dioxolan-4-ones derived from chiral mandelic and lactic acid ($\text{2a}$, $\text{2b}$; $\text{3a}$; $\text{10a}$, $\text{10b}$) were alkylated with high stereoselectivity. The products formed were hydrolysed to α-hydroxy acids with 65–85% e.e. ((S)(+)-$\text{5}$,$\text{7}$,$\text{9}$, (R)(–)-$\text{13}$).     

Fluorinated isocyanates - reactions with fluorinated anhydrides,acids, and related substrates

$\text{F}$-Phenylisocyanate reacts with cyclic or linear anhydrides with the aid of catalysts to form $\text{F}$-(N-arylimides) in good yields. Similar reactions with fluorinated acids lead directly to amides. This isocyanate undergoes smooth reaction with various substrates (hexafluoroacetone, trioctylphospine oxide, and itself). Several reactions between $\text{F}$-aryl and $\text{F}$-alkyl isocyanates are compared. Reaction between the latter and $\text{F}$-anhydrides or acids gives products derived from fluoride ion transfer reactions.     

The anhydride structure of several previously reported stable areneselenenic acids1

The compounds previously reported² to be the stable areneselenenic acids, $\text{o}$-nitro-($\text{la}$ and $\text{+o}$-benzoylbenzeneselenenic acid ($\text{lb}$), are shown actually to be the corresponding selenenic anhydrides (ArSeOSeAr). Solutions of the selenenic acids (ArSeOH), however, can be easily generated from the anhydrides byacid-catalyzed hydrolysis.     

Regiospecific alkylation of tetronic acids : Formation of 4-alkoxy-5H-furan-2-ones and 2-alkoxy-5H-furan-4-ones

2-Alkoxy-5$\text{H}$-furan-4-ones (7,8) and 4-alkoxy-5$\text{H}$-furan-2-ones (4,5) were prepared regiospecifically and in high yields from tetronic acids (4-hydroxy-5$\text{H}$-furan-2-ones) (2) in the first case by acetylating the 4-OH group and then reacting with trialkyloxonium tetrafluoroborate, and in the second case by alkylating tetrabutylammonium tetronates with dialkyl sulfate, respectively. Direct alkylation of tetronic acids with trialkyloxonium tetrafluoroborate gave in four cases regiospecific 2-O-alkylation, in one case 4-O-alkylation and in two other cases mixtures of 2- and 4-alkoxy derivatives.     

A tandem michael reaction-cycloalkylation utilizing 2-nitropropane: a facile route to the acid component of insecticidal pyrethroids

Treatment of three representative β-substituted-α-cyanoacrylates ($\text{2}$) with 2-nitropropane and potassium carbonate in refluxing ethanol afforded stereoselectively cyclopropanoid precursors ($\text{4}$) to 3-substituted-2,2-dimethylcyclopropanecarboxylic acids ($\text{7}$).     

Short,stereocontrolled syntheses of irreversible eicosanoid biosynthesis inhibitors. 5,6- , 8,9- , and 11,12-dehydroarachidonic acid

5,6- and 11,12-dehydroarachidonic acids ($\text{1}$ and $\text{3}$), which $\text{irreversibly}$ inhibit leukotriene and prostaglandin biosynthesis, respectively, have been synthesized, along with the 8,9-isomer ($\text{2}$), by novel and direct routes.     

A highly effective asymmetric synthesis of α-hydroxy acids by alkylation of chiral n-(benzyloxyacetyl)-trans-2,5-bis(methoxymethoxymethyl)pyrrolidine

Alkylation of lithiated $\text{N}$-(benzyloxyacetyl)-$\text{trans}$-2,5-bis(mehtoxyymethoxymethyl)- pyrrolidine proceeded with high stereoselectivity (≥96% de) and subsequent transformations of the alkylated products gave synthetically useful α-benzyloxy acids or α-hydroxy acids of high enantiomeric purity.     

Trimethylsilyl trichloroacetate: a new reagent for salt-free silylations

Trimethylsilyl trichloroacetate ($\text{1}$) is a convenient reagent for the silylation of phenols, carboxylic acids, mercaptans, amides, acetylenes, and β-keto esters, while the reaction of $\text{1}$ with aldehydes and ketones affords silylated trichloromethyl carbinols ($\text{5}$).     

A simple process for the purification of arachidonic acid

Pure arachidonic acid ($\text{1}$) and docosahexanoic acid ($\text{3}$) are available by a two-step purification method from commercial 50% acids with high efficiency.     

An efficient and stereoselective synthesis of platelet-activating factors and the enantiomers from D- and L- tartaric acids

Acetyl glyceryl ether phosphorylcholines, platelet-activating factors ($\text{1}$ and $\text{2}$), were efficiently synthesized in a stereochemically unambiguous manner starting from D- and L- tartaric acids as the chiral synthons.     

Synthesis of erythro- and threo-α-bromo-α′-fluorosuccinic acids

$\text{erythro}$- and $\text{threo}$-α-Bromo-α′-fluorosuccinic acids have been prepared from their corresponding dimethyl esters. Because of the extreme readiness of elimination of hydrogen fluoride in basic medium, a special method of acid hydrolysis had to be applied. Hydrogen and fluorine NMR spectra are reported.     

Synthèse et thermolyse de dérivés disilyles des acides hydroxamiques : Sur une nouvelle voie d'accès aux esters isocyaniques et aux amines

Thermolysis of disilylated hydroxamic acids $\text{7}$, readily prepared from hydroxamic acids $\text{5}$ and hexamethyl disilazane, leads to the corresponding isocyanates $\text{4}$ ; an application to the synthesis of amines is reported.     

Oxidative decarboxylation of [n.2.2]propellane carboxylic acids with lead tetraacetate. rearrangement approach to bicyclo [n.2.2.]bridgehead alkenes.

Oxidative decarboxylation of [n.2.2]propellane carboxylic acids ($\text{1a}$-$\text{c}$) with lead tetraacetate gave the bicyclic acetates ($\text{2b}$, $\text{c}$) having a bridgehead double bond and/or the tricyclic acetates ($\text{3a}$, $\text{b}$) in good yields. Vapor phase thermolysis of $\text{3a}$ or $\text{3b}$ afforded the bridgehead olefin $\text{2a}$ or $\text{2b}$ quantatively.     

Stereochemical studies 83 saturated heterocycles 76 : Preparation and conformational study of partially saturated 3,1-benzoxazines, 3,1-benzoxazin-2-ones and 3,1-benzoxazine-2-thiones

The $\text{cis}$- and $\text{trans}$-2-amino-4-cyclohexene-1-carboxylic acids $\text{1}$ and $\text{3}$ react with imidates to give the condensed-skeleton, bicyclic $\text{cis}$- and $\text{trans}$-pyrimidin-4-ones $\text{8}$ and $\text{9}$. The amino acids $\text{1}$ and $\text{3}$ were reduced to the $\text{cis}$-and $\text{trans}$-1, 3-aminoalcohoIs $\text{6}$ and $\text{7}$, which were cyclized by means of imidates to the bicyclic tetrahydro-4$\text{H}$-3,1-benzoxazines $\text{10}$ and $\text{11}$, or were converted, $\text{via}$ the corresponding carbamates $\text{14}$ and $\text{15}$ into the tetrahydro-4$\text{H}$-3,1-benzoxazin-2(1$\text{H}$)-ones $\text{16}$ and $\text{17}$. The 2-thioxo analogues $\text{18}$ and $\text{19}$ were prepared by cyclization of the dithiocarbamates obtained from the aminoalcohols $\text{6}$ and $\text{7}$ by treatment with carbon disulphide. The $\text{trans}$-aminoalcohol $\text{7}$ and its saturated analogue reacted with $\text{p}$-chlorobenzaldehyde to furnish the hexahydro $\text{13}$ and octahydro-4$\text{H}$-3,1-benzoxazine $\text{13a}$, respectively. ¹H and ¹³C NMR studies showed that, similarly to the earlier-investigated analogues containing oxygen or unsubstituted nitrogen at position 1, the synthesized $\text{cis}$ isomrs $\text{8}$, $\text{10}$, $\text{16}$ and $\text{18}$ occurred as the preferred conformer in the heterocyclic twist inverse form of $\text{N}$-inside type ($\text{quasiaxial}$ C₆-N bond) (B). In the $\text{trans}$ isomers containing a saturated C-2 atom ($\text{13}$ and $\text{13a}$), H-2 and H-6 are in $\text{cis}$ relative positions.