Gernot A. Eller

Composition and Antioxidant Activities of the Essential Oil of Cinnamon (Cinnamomum zeylanicum Blume) Leaves from Sri Lanka

Abstract The composition of the volatiles from leaves of Cinnamomum zeylanicum Blume from Sri Lanka was studied by GC-FID and GC-MS. The basic component of the oil was found to be eugenol (74.9%), followed by β-caryophyllene (4.1%), benzyl benzoate (3.0%), linalool (2.5%), eugenyl acetate (2.1%) and cinnamyl acetate (1.8%). The essential leaf oil from cinnamon demonstrated scavenger activity against the DPPH radical at concentrations which are lower than the concentrations of eugenol, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA). This essential cinnamon oil showed also a significant inhibitory effect on hydroxyl radicals and acted as an iron chelator. Cinnamon leaf oil efficiently inhibited the formation of conjugated dienes and the generation of secondary products from lipid peroxidation at a concentration equivalent to that of the standard BHT.

Heterocyclic analogs of thioflavones: synthesis and NMR spectroscopic investigations.

The synthesis of several hitherto unknown heterocyclic ring systems derived from thioflavone is described. Coupling of various o-haloheteroarenecarbonyl chlorides with phenylacetylene gives 1-(o-haloheteroaryl)-3-phenylprop-2-yn-1-ones, which were treated with NaSH in refluxing ethanol to yield the corresponding bi- and tricyclic annelated 2-phenylthiopyran-4-ones. Detailed NMR spectroscopic investigations of the ring systems and their precursors are presented.

First Synthesis of 3-Acetyl-2-aminothiophenes Using the Gewald Reaction

Novel 3-acetyl-2-aminothiophenes were prepared from cyanoacetone and 1,4-dithianyl-2,5-diols using a modified Gewald reaction. The syntheses of the corresponding acetamides, as well as that of 3-acetyl-2-amino-5-nitrothiophene - an interesting building-block for thiophene azo dyes - are reported. Detailed spectroscopic investigations ((1)H-NMR, (13)C-NMR, MS, IR) of the obtained compounds are presented.

THE 4-METHOXYBENZYL (PMB) FUNCTION AS A VERSATILE PROTECTING GROUP IN THE SYNTHESIS OF N-UNSUBSTITUTED PYRAZOLONES

Starting from diethyl ethoxyrnethylenemalonate and 4-methoxy-benzylhydrazine (PMB-NHNH 2 ) 2-(4-methoxybenzyl)-2,4-dihydro-3H-pyrazol-3-one was prepared. Reaction of the latter with carboxylic acid chlorides / calcium hydroxide in 1,4-dioxane afforded 4-acyl-5-hydroxy-1-PMB-1H-pyrazoles, whereas with dimethylformamide diethyl acetal or benzaldehyde the corresponding (E)-4-dimethylaminomethylene or (E)-4-benzylidene products, respectively, were obtained. The PMB protecting group could be conveniently removed from the pyrazole nucleus by treatment with trifluoroacetic acid to give the N-unsubstituted pyrazolones. Detailed NMR spectroscopic investigations ( 1 H, 1 3 C, 1 5 N) with the obtained compounds are presented.

Composition and Antimicrobial Activity of Cymbopogon giganteus (Hochst.) Chiov. Essential Flower, Leaf and Stem Oils from Cameroon

Abstract The essential oils of fresh flowers (2 samples), leaves and stems of Cymbopogon giganteus (Hochst.) Chiovenda from Cameroon were investigated by GC and GC/MS. More than 55 components have been identified in the samples 1 (flowers 1), 2 (leaves), 3 (stems) and 4 (flowers 2) with main compounds possessing the p-menthadiene skeleton as follows: cis-p-mentha-1(7),8-dien-2-ol (1: 22.8%, 2: 27.7%, 3: 29.1%, 4: 20.5%), trans-p-mentha-1(7),8-dien-2-ol (1: 24.9%, 2: 21.6%, 3: 28.1%, 4: 26.5%), trans-p-mentha-2,8-dien-1-ol (1: 17.3%, 2: 22.1%, 3: 21.4%, 4: 16.3%) and cis-p-mentha-2,8-dien-1-ol (1: 8.3%, 2: 5.4%, 3: 4.6%, 4: 9.7%). Additional components in higher concentrations, responsible for the characteristic aroma impressions of these samples are especially limonene, trans-verbenol and carvone as well as some other mono- and sesquiterpenes. Antimicrobial activities of the four oils were found against Gram-(+)- and Gram-(-)-bacteria as well as the yeast Candida albicans, and these results were discussed with the compositions of each sample.

Synthesis of novel polycyclic ring systems containing two pyrano[2,3-c]pyrazol-4-(1H)one moieties

Novel penta-or heptacyclic ring systems containing two pyrano[2,3-c]pyrazol-4(1H)-one units are prepared in one or two steps from the reaction of 3-methyl-1-phenyl-2-pyrazolin-5-one and bis(o-chlorocarbonyl chlorides) derived from benzene-or 1,10-phenanthroline.

Sonogashira Coupling Offers a New Synthetic Route to Thieno[2,3-c]pyrazoles

Abstract 1,3-Disubstituted-5-chloro-4-iodopyrazoles are selectively coupled with phenylacetylene under typical Sonogashira reaction conditions [PdCl2(PPh3)2, CuI, Et3N, dimethylformamide (DMF)] to obtain the corresponding 5-chloro-4-(phenylethynyl)pyrazoles in good yield. The latter are smoothly cyclized with Na2S in DMF into the corresponding thieno[2,3-c]pyrazoles. Detailed spectroscopic investigations (1H, 13C, and 15N NMR, mass, and infrared) of all compounds are reported.

Derivatives of pyrazinecarboxylic acid: 1H, 13C and 15N NMR spectroscopic investigations.

NMR spectroscopic studies are undertaken with derivatives of 2‐pyrazinecarboxylic acid. Complete and unambiguous assignment of chemical shifts (1H, 13C, 15N) and coupling constants (1H,1H; 13C,1H; 15N,1H) is achieved by combined application of various 1D and 2D NMR spectroscopic techniques. Unequivocal mapping of 13C,1H spin coupling constants is accomplished by 2D (δ,J) long‐range INEPT spectra with selective excitation. Phenomena such as the tautomerism of 3‐hydroxy‐2‐pyrazinecarboxylic acid are discussed. Copyright

Heterocyclic analogs of xanthiones: 5,6‐fused 3‐methyl‐1‐phenylpyrano[2,3‐c]pyrazol‐4(1H) thiones—synthesis and NMR (1H, 13C, 15N) data

Various [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐thiones were synthesized in high yields by treatment of the corresponding [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐ones with Lawessons reagent. Detailed NMR spectroscopic studies were undertaken of the title compounds. Complete and unambiguous assignment of chemical shifts (1H, 13C, 15N) and coupling constants (1H,1H; 13C,1H) was achieved by the combined application of various one‐ and two‐dimensional (1D and 2D) NMR spectroscopic techniques. Unequivocal mapping of most 13C,1H spin coupling constants is accomplished by 2D (δ, J) long‐range INEPT spectra with selective excitation. Copyright

A one-step synthesis of pyrazolone

Substituted 2-pyrazolin-5-ones play an important role as substructures of numerous pharmaceuticals, agrochemicals, dyes, pigments, as well as chelating agents and thus attract remarkable attention [1,2].[...]