Eugenol and safrole as starting materials for the synthesis of 3-alkyl muconic acid mono and dimethyl esters and 4,4-dialkyl butenolides

Compounds $\text{1b-e}$ and $\text{2b-d}$ prepared from eugenol ($\text{1a}$) and safrole ($\text{2a}$) respectively were submitted to ozonation in methanol at 0°C. The 3-alkyl muconic acid dimethyl esters $\text{4b-e}$ were produced from $\text{1b-e}$ (～ 45%), while starting from $\text{2b-d}$ the 3-alkyl muconic acid monomethyl esters $\text{6b-d}$ were obtained regiospecifically (～ 75%). These latter compounds were transformed (～ 85%) into the 4,4-dialkyl butenolides $\text{7b-d}$.     

Plaunol A and B,new anti-ulcer diterpenelactones from Crotonsublyratus

Two new diterpenelactones named plaunol A ($\text{2}$) and B ($\text{3}$) exhibiting anti-Shay ulcer activity were isolated from Thai medicinal plant, $\text{Croton}$$\text{sublyratus}$. Structure of $\text{2}$ was determined by X-ray analysis of its $\text{p}$-bromobenzoate and structure of $\text{3}$ was deduced from the results of chemical correlation and the spectral data.     

Formal total synthesis of β-pipitzol

(±)-$\text{O}$-methylperezone ($\text{1b}$) was obtained by selective oxidative demethylation of (±)-leucoperezone trimethyl ether ($\text{4a}$). Compound ($\text{4a}$) was prepared by condensation of 2,3,5-trimethoxytoluene ($\text{5e}$) with 6-methyl-5-hepten-2-one, followed by reductive removal of the tertiary alcohol. The aromatic precursor $\text{5e}$ was prepared in four steps from 2,3-dimethoxytoluene ($\text{5a}$) and, alternatively, in three steps from 5-bromoveratraldehyde ($\text{6a}$). Racemic $\text{1b}$ and $\text{4a}$ were directly compared with the optically active molecules prepared from natural R(-)-perezone ($\text{1a}$).     

Five new steroidal glycosides,pregnedioside-A, -B,and their three monoacetates,from an Okinawan soft coral of Alcyonium sp.

Five new pregnene-type steroidal glycosides, named pregnedioside -a ($\text{1}$), 4′-O-acetyl-pregnedioside-a ($\text{2}$), 3′-O-acetyl-pregnedioside-a ($\text{3}$), pregnedioside-b ($\text{5}$), and 4′-O-acetyl-pregnedioside-b ($\text{6}$), were isolated from an Okinawan soft coral of Alcyonium sp. and their structures were elucidated. These are rare examples of steroidal gylcosides from soft coral.     

Botrydienal,a new prytotoxin,and its related metabolites,dehydrobotrydienal and deacetyldihydrobotrydial produced by botryotiniasquamosa

A new phytotoxin, botrydienal, and its two related metabolites, dehydrobotrydienal and deacetyldihydrobotrydial, were isolated from $\text{Botryotinia}$$\text{squamosa}$, and their structures were elucidated as $\text{1}$, $\text{2}$ and $\text{3}$, respectively, on the basis of spectral analysis.     

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)(–)-$\text{13}$).     

Stereochemical studies—76 saturated heterocycles—63 : synthesis of cis- and trans-n-methyl- and n-benzyl-4.5- and 5,6-tetramethylenetetrahydro-1,3-oxazines; an x-ray study of n-benzyl-cis-4,5-tetramethylenetetrahydro-1,-3-oxazinium- picrate

- The corresponding $\text{cis}$- and $\text{trans-N}$-methyl- and $\text{N}$-benzyl-5,6- and 4,5-tetramethylenetetrahydro-l,3-oxazines $\text{(5a,b-8a,b)}$were synthesized from $\text{cis}$- and $\text{trans-N}$-methyl and$\text{N}$-benzyl-2- aminomethyl-1-cyclohexanols $\text{1a,b,2a,b}$, from $\text{cis}$- and $\text{trans-N}$-methyl- and $\text{N}$benzyl -2-hydroxymethyl-1-cyclohexylamines$\text{(3a,b,4a,b)}$ by reaction with formaldehyde. The aminoalcohols $\text{1a,2a,3a,b}$and $\text{4a,b}$ were prepared in considerably higher yields than in earlier procedures. NMR spectroscopy showed that the $\text{cis}$ isomers of the synthesized oxazines were conformationally homogeneous in solution, and their preferred conformation (inside or outside) depended on the steric requirement of the groups attached to the anellation points, whereas a bulky C-2 substituent had no influence on the predominant conformation. The structure of $\text{N}$-benzyl-$\text{cis}$-4,5-tetramethylenetetrahydro-1,3-oxaziniumpicrate $\text{(7b)}$. determined by X-ray diffraction analysis, was in agreement with the predominant N-outside conformation of the corresponding base, established by means of NMR spectroscopy.     

Synthesis of optically active leukotriene (SRS-A) intermediates

In an approach to SRS-A and analogues thereof, the key (5$\text{S}$, 6$\text{S}$)-epoxy alcohol $\text{9}$ and its 6-epimer $\text{18}$ were prepared starting from $\text{D}$-araboascorbic acid and $\text{L}$-diethyl tartrate, respectively.     

Epoxide formation by the photolysis of cyclic oxalate esters

The cyclic oxalate esters from $\text{meso}$- and $\text{d}$, $\text{1}$-hydrobenzoin were prepared and photolyzed. $\text{Meso}$-hydrobenzoin oxalate gave only $\text{cis}$-stilbene oxide upon photolysis while the $\text{d}$, $\text{1}$ isomer gave $\text{trans}$-stilbene oxide.     

Sesquiterpenes from termite soldiers. Structure of amiteol,a new 5β, 7β, 10β-eudesmane from amitermesexcellens

The defense secretions of termite soldiers in the genera $\text{Amitermes}$, $\text{Noditermes}$, and $\text{Prorhinotermes}$ contain sesqueterpene hydrocarbons, alcohols and ethers. Three new eudesmanes possessing the hitherto unknown 5β, 7β, 10β configuration were identified from $\text{Amitermes}$$\text{excellens}$.     

A new method of carbon extension at C-4 of azetidinones

Azetidinone carboxylates $\text{7}$, $\text{9}$ and $\text{11}$ were prepared starting from 4-thia azetidinones and carbenes derived from diazoesters.     

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.     

Four new prostanoids: Claviridenone-A, -B, -C,and -D from the okinawan soft coral Clavularia viridis

The structures of four new prostanoids named claviridenone-a, -b, -c, and -d, which were isolated from the Okinawan soft coral Clavularia viridis, were elucidated as $\text{1}$, $\text{2}$, $\text{3}$, and $\text{4}$, respectively.     

Synthesis and NMR study of norbornane/norbornene-fused tetracyclic azetidinones

Tetracyclic azetidinones$\text{8}$,$\text{9}$ and $\text{12}$–$\text{17}$ were synthesized. In the cases of$\text{8}$ and$\text{9}$, the main component was isolated from the two-component product of the cycloaddition. The minor component was concentrated to give a mixture, from which a computer technique utilizing the known spectrum of the main component gave the proton resonance spectrum also of the minor component. Only one diastereomer could be isolated for the each of the analogues$\text{12}$–$\text{17}$. Reaction of the 1,3-oxazine $\text{3}$ with chloroacetyl chloride gave, besides the azetidinone $\text{12}$, the 1,3-oxazine [2,3-$\text{b}$]-1,3-oxazin-4-one derivative$\text{18}$. Configurations and conformations were determined by IR, ¹H and ¹³C NMR spectroscopy.     

Clavulones,new type of prostanoids from the stolonifer clavulariaviridis quoy and gaimard

Three new prostanoids, clavulone I($\text{1}$), II($\text{2}$) and III($\text{3}$), were isolated from the Japanese Stolonifer $\text{Claularia}$$\text{viridis}$ Quoy and Gaimard. The structures of these prostanoids were determined on the basis of spectral data and chemical reactions.     

Marine natural products: fistularin-1, -2 and -3 from the sponge Aplysina fistularis forma fulva

Three new high molecular weight bromotyrosine-related metabolites, $\text{3a}$, $\text{4a}$ and $\text{5a}$, were isolated from the sponge Aplysina ( Verongia) fistularis forma fulva, and their structures were determined from high resolution ¹H NMR and other spectroscopic data. The new metabolites are formally derived by combination of major segments of two known Aplysina metabolites $\text{1a}$ and $\text{2}$.     

Minor and trace sterols in marine invertebrates 30. Isolation,structure elucidation and partial synthesis of 26-methylstrongylosterol and 28-methylxestosterol - two marine sterols arising by a novel quadruple biomethylation sequence

Two new sterols, 26-methylstrongylosterol ($\text{4}$) and 28-methylxestosterol ($\text{5}$), arising from a hitherto unknown quadruple biomethylation sequence, together with the biogenetically important “missing link”, durissimasterol ($\text{6}$), were isolated from the Indo-Pacific sponge $\text{Strongylophora}$$\text{durissima}$.     

Isolation and structures of trans-laurencenyne,a possible precursor of the C15 halogenated cyclic ethers,and trans-neolaurencenyne from laurencia okamurai

Isolation and structural elucidation of two new acetylenic polyenes, $\text{trans}$-laurencenyne $\text{1}$ and $\text{trans}$-neolaurencenyne $\text{2}$ from the marine red alga $\text{Laurencia okamurai}$ were carried out, the former compound $\text{1}$ very recently being proposed to be a biosynthetic precursor of the C₁₅ halogenated cyclic ethers, $\text{7}$ and $\text{8}$.     

Synthetic studies on β-lactam antibiotics. 18. Convenient,stereocontrolled synthesis of 3-methyl 7α-methoxy-1-oxacephems

Alcohols $\text{4}$ and $\text{8}$, prepared from $\text{3}$, underwent completely stereospecific etherification to give 1-oxacephams $\text{5}$ and $\text{10}$, which were converted into the 1-oxacephem nucleus $\text{1b}$ via $\text{6}$ and $\text{1c}$. Functionalization at C-3′ in $\text{6}$ and $\text{1c}$ was unsuccessful.     

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.