Stereospecific total synthesis of 12-(r)- and 12- (s)-forms of 6-trans leukotriene B

Non enzymatic hydration of leukotriene A ($\text{1}$), the biogenetic precursor of leukotriene B ($\text{2}$) affords among other products two diastereomeric 6-$\text{trans}$-isomers of 2, the first stereospecific and efficient syntheses of which are recorded herein.     

Stereocontrolled (E,Z and erythro, threo) synthesis of ⊙-hydroxyallylic sulphides

All four isomers of substituted 3-alkylthio-4-hydroxybutenes have been synthesised: both the geometry of the double bond and the relative stereochemistry of the two chiral centres are controlled.     

A short synthesis of (s)-5-hydroxymethyl-(5h)-furan-2-one and derivatives from d-ribonolactone

We describe a short synthesis of ($\text{S}$)-5-hydroxymethyl-(5$\text{H}$-furan-2-one and some 5-O-derivatives, which are being used as key starting products for the synthesis of several antileukaemic lignan lactones, from $\text{D}$-ribonolactone.     

Synthesis of the enantiomeric forms of cis and trans 1-benzyloxy-2,3-epoxy butane and of (3S,4S) 4-methyl-3-heptanol

The C₄erythro and threo diols (7) and (8) are converted either into the chiral epoxides (13) and (15) or into the enantiomers (14) and (16); the epoxide (13) is used as chiral synthon for the preparation of (3$\text{S}$,4$\text{S}$) 4-methyl-3-heptanol (21).     

Autorecycling oxidation of alcohol catalyzed by 1,3,7,9,11,12,14-heptazapentacene-2,4,8,10 (14H,3H,9H,12H)-tetraones (mixed flavins)

1,3,7,9,11,12,14-Heptazapentacene-2,4,8,10 (14$\text{H}$,3$\text{H}$,9$\text{H}$,12$\text{H}$)-tetraones (mixed flavins) were prepared by the cyclization of 1,5-dihydro-8-[N-alkyl-N-(5-nitrouracil-6-yl)-amino-5-deazaflavins with Vilsmeier reagent. The mixed flavins oxidized alcohol under neutral condition in sunlight and a remarkable autorecycling was observed.     

Die Schwingungsspektren der isomeren Komplexe N,N′-Bis(dimethylgallium)-cis- und trans-N,N′-dimethyloxamideine kritische Analyse

Reaction of Ga(CH₃)₃ with N,N′-dimethyloxamide affords two isomeric N,N′-bis(dimethylgallium)-N,N′-dimethyloxamide complexes, characterized by crystal structure analysis as having cis-and trans-configuration with respect to the central oxamide CC bond and belonging to the point groups C_2v (cis) and C_2h (trans), respectively. Both isomers which are formed in varying ratio, depending upon the reaction conditions, have been isolated in pure form; their vibration spectra (IR/RE) are analyzed in detail in points of alternative behaviour, and are assigned in all bands, especially in the G-C and Ga-X frequency region. The assignment receives further confirmation from a comparison with the vibrational data of the homologous N,N′-bis(dimethylgallium)oxamide (cis/trans isomer mixture).     

N-Acylated α-aminonitriles and their conversion into 5-aminooxazole, 5(4h)-oxazolone and 4(5h)-imidazolone derivatives

In contrast with the reaction of α-aminonitriles $\text{1}$a, the corresponding $\text{N}$-acylated α-aminonitriles $\text{1}$b-f and oxalyl chloride do not yield pyrazinone derivatives, but 5-aminooxazoles $\text{9}$-$\text{11}$ or 4(5$\text{H}$)-imidazolones $\text{12}$, the latter being converted in some cases into imidazo [2,1-$\text{a}$]isoquinoline-2,5,6(3$\text{H}$)-triones. Reactions of compounds $\text{1}$b-f and ethyl chlorooxoacetate provide evidence for a 5(4$\text{H}$)-iminooxazole intermediate $\text{7}$, which aromatizes to yield 5-aminooxazoles $\text{9}$-$\text{11}$; however, unaromatizable īntermediates of type $\text{7}$ - isolable as 5(4$\text{H}$)y-oxazolones $\text{13}$ after hydrolysis - undergo a catalyzed Dimroth-type rearrangement to give imidazolone derivatives $\text{12}$.     

Stereoselective synthesis of (1R,3R,5S-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane

(1$\text{R}$,3$\text{R}$,5$\text{S}$)-1,3-Dimethyl]-2,9-dioxabicyclo[3.3.1]nonane $\text{1}$ has been stereoselectively synthesized based on a highly stereoselective method for the synthesis of 1,3-$\text{syn}$-polyol.     

Synthesis of Lobesia botrana and Spodoptera littoralis natural sex-attractants

Starting from the coupling reaction of alkyl cuprates with 1-alkynyl-2-propenyl acetates, the title compounds were prepared by short convenient syntheses.     

Enantiocontrolled synthesis of (S)-3-substituted cycloalkanones from (s)-2-(p-tolylsulfinyl)-2-cycloalkenones and diorganomagnesium reagents.

By appropriate choice of reaction conditions, the $\text{same}$ enantiomerically pure ($\text{S}$)-(+)-2-($\text{p}$-tolylsulfinyl)cycloalkenone can be converted into $\text{either}$ an ($\text{R}$)-or an ($\text{S}$)-3-substituted cycloalkanone in good to excellent enantiomeric purity.     

Diastereoselective synthesis of N-acetyl-D,L-acosamine and N-benzoyl-D,L-ristosamine

N-Acyl derivatives of $\text{D}$,$\text{L}$-acosamine and $\text{D}$,$\text{L}$-ristosamine were synthesized with high stereo selectivity utilizing intramolecular Michael addition of γ- and δ-carbomoyloxy-α,β-unsaturated esters.     

Rotational isomerism between the E and Z forms of o-substituted benzo-N-methyl hydroxamic acids in strong acid

The $\text{E}$∠$\text{Z}$ equilibrium of the cations of benzo hydroxamic acids, in mineral acid, was studied utilizing ¹H NMR spectroscopy, NOEDS and MNDO claculations     

[2+2] Cycloaddition of benzyne to cis,trans- and cis,cis-1,5-cyclooctadiene

The relative rates of formation of $\text{cis}$ and $\text{trans}$ [2+2]cycloadducts of benzyne to $\text{cis}$, $\text{trans}$- and $\text{cis}$, $\text{cis}$-1,5-cyclooctadiene, $\text{trans}$- and $\text{cis}$-cyclooctene are discussed and properties of the adducts (e.g., their unusual hydrogenation) are described.