- Synthesis and mass spectra of rearrangement bio-signature metabolites of anaerobic alkane degradation via fumarate addition
-
Metabolite profiling in anaerobic alkane biodegradation plays an important role in revealing activation mechanisms. Apart from alkylsuccinates, which are considered to be the usual biomarkers via fumarate addition, the downstream metabolites of C-skeleton rearrangement can also be regarded as biomarkers. However, it is difficult to detect intermediate metabolites in both environmental samples and enrichment cultures, resulting in lacking direct evidence to prove the occurrence of fumarate addition pathway. In this work, a synthetic method of rearrangement metabolites was established. Four compounds, namely, propylmalonic acid, 2-(2-methylbutyl)malonic acid, 2-(2-methylpentyl)malonic acid and 2-(2-methyloctyl)malonic acid, were synthesized and determined by four derivatization approaches. Besides, their mass spectra were obtained. Four characteristic ions were observed at m/z 133 + 14n, 160 + 28n, 173 + 28n and [M - (45 + 14n)]+ (n = 0 and 2 for ethyl and n-butyl esters, respectively). For methyl esterification, mass spectral features were m/z 132, 145 and [M - 31]+, while for silylation, fragments were m/z 73, 147, 217, 248, 261 and [M - 15]+. These data provide basis on identification of potential rearrangement metabolites in anaerobic alkane biodegradation via fumarate addition.
- Chen, Jing,Zhou, Lei,Liu, Yi-Fan,Hou, Zhao-Wei,Li, Wei,Mbadinga, Serge Maurice,Zhou, Jing,Yang, Tao,Liu, Jin-Feng,Yang, Shi-Zhong,Wu, Xiao-Lin,Gu, Ji-Dong,Mu, Bo-Zhong
-
-
- Effect of regioregularity and role of heteroatom on the chiral behavior of oligo(heteroalkyl thiophene)s
-
Novel optically active oligothiophenes bearing electron-donating chiral side chains have been prepared by synthetic methods suitable to achieve regioregular head-to-tail and head-to-head/tail-to-tail derivatives. In particular, the chiral (S)-(2-methyl)butyl moiety was linked at position 3 of the thiophene ring through heteroatoms, such as S or O, to evaluate its effect on the macro molecular aggregation and, consequently, on the chiroptical properties of the material in the solid state. The materials have been fully characterized and investigated by optical and chiroptical methods upon aggregation both from the solution and as cast films. Compared with the related head-to-tail and head-to-head/tail-to-tail poly(3-alkyl)thiophene derivatives, with the same optically active moiety directly linked to the ring and possessing a higher polymerization degree, the chiroptical properties of the newly synthesized oligomers were significant, or even better, and provided insight into the role of intrachain–interchain interactions between the heteroatom and the thienyl sulfur atom.
- Marinelli, Martina,Angiolini, Luigi,Lanzi, Massimiliano,Di Maria, Francesca,Salatelli, Elisabetta
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supporting information
p. 1361 - 1376
(2020/11/23)
-
- Yakushinamides, Polyoxygenated Fatty Acid Amides That Inhibit HDACs and SIRTs, from the Marine Sponge Theonella swinhoei
-
Yakushinamides A (1) and B (2), prolyl amides of polyoxygenated fatty acids, have been isolated from the marine sponge Theonella swinhoei as inhibitors of HDACs and SIRTs. Their planar structures were determined by interpretation of the NMR data of the intact molecules and tandem FABMS data of the methanolysis products. For the assignment of the relative configurations of the three contiguous oxymethine carbons in 1 and 2, Kishi's universal NMR database was applied to the methanolysis products. During the assignments of relative configurations of the isolated 1-hydroxy-3-methyl moiety in 1 and the isolated 1-hydroxy-2-methyl moiety in 2, we found diagnostic NMR features to distinguish each pair of diastereomers. The absolute configurations of 1 and 2 were determined by a combination of the modified Mosher's method and Marfey's method. Although the modified Mosher's method was successfully applied to the methanolysis product of 1, this method gave an ambiguous result at C-20 when applied to the methanolysis product of 2, even after oxidative cleavage of the C-14 and C-15 bond.
- Takada, Kentaro,Imae, Yasufumi,Ise, Yuji,Ohtsuka, Susumu,Ito, Akihiro,Okada, Shigeru,Yoshida, Minoru,Matsunaga, Shigeki
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p. 2384 - 2390
(2016/10/04)
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- Straightforward synthesis of all stenusine and norstenusine stereoisomers
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All the stereoisomers of stenusine (1) and norstenusine (21) have been efficiently synthesized by the asymmetric hydrogenation of pyridines. The (2R,3S)- and (2R,3R)-isomers of 1, that are difficult to prepare, have been synthesized for the first time using a chemoenzymatic approach in eight steps with an 8 % total yield. All the target compounds were obtained in good stereochemical purity by using very simple and inexpensive reagents and auxiliaries. All the stereoisomers of the defensive alkaloids stenusine and norstenusine produced by Stenus beetles have been synthesized in a straightforward manner. The chiral (S) side chain is derived from (S)-2-methyl-1-butanol. For the difficult preparation of (R)-3-(2-methylbutyl) pyridine, a highly efficient chemoenzymatic approach was developed.
- Mueller, Tobias,Dettner, Konrad,Seifert, Karlheinz
-
experimental part
p. 6032 - 6038
(2011/12/15)
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- New syntheses of 1,7-dimethylnonyl propanoate, the western corn rootworm pheromone, in four different ways via cross metathesis, alkylation and coupling reactionsss
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A mixture of the four stereoisomers of 1,7-dimethylnonyl propanoate, the female sex pheromone of the western corn rootworm (Diabrotica virgifera virgifera LeConte), was synthesized in four different ways by employing one of the following four reactions as the key step: (i) cross metathesis using the Grubbs I catalyst, (ii) cross metathesis using the Grubbs II catalyst, (iii) alkylation of an alkynide anion, and (iv) Grignard coupling in the presence of dilithium tetrachlorocuprate. Although the cross metathesis approaches enabled two short syntheses (4 or 6 steps) of the pheromone to be achieved, the cheapest and most efficient synthesis was possible via Grignard coupling to give the desired pheromone in a 40% overall yield based on 2-methyl-1-butanol (8 steps).
- Mori, Kenji
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p. 595 - 600
(2011/04/23)
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- Pheromone synthesis. Part 243: Synthesis and biological evaluation of (3R,13R,1′S)-1′-ethyl-2′-methylpropyl 3,13-dimethylpentadecanoate, the major component of the sex pheromone of Paulownia bagworm, Clania variegata, and its stereoisomers
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All of the four stereoisomers of (1′S)-1′-ethyl-2′-methylpropyl 3,13-dimethylpentadecanoate, the major component of the female sex pheromone of Clania variegata, were synthesized by employing olefin cross metathesis as the key reaction and starting from (R)- or (S)-2-methyl-1-butanol, (R)- or (S)-citronellal, and (S)-2-methyl-3-pentanol. Their bioassay revealed the (3R,13R,1′S)-isomer as the bioactive one, whose more efficient synthesis was achieved in two different ways by employing Wittig reaction as the key step.
- Mori, Kenji,Tashiro, Takuya,Zhao, Boguang,Suckling, David M.,El-Sayed, Ashraf M.
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experimental part
p. 2642 - 2653
(2010/05/18)
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- Synthesis of all the four stereoisomers of (1′S)-1-ethyl-2-methylpropyl 3,13-dimethylpentadecanoate, the major component of the sex pheromone of Paulownia bagworm, Clania variegata
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All the four stereoisomers of (1′S)-1-ethyl-2-methylpropyl 3,13-dimethylpentadecanoate, the major component of the sex pheromone of Clania variegata, were synthesized by starting from (R)- or (S)-2-methylbutan-1-ol, (R)- or (S)-citronellal, and (S)-2-methylpentan-3-ol. Olefin cross metathesis was employed as the key reaction.
- Mori, Kenji,Tashiro, Takuya
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scheme or table
p. 3266 - 3269
(2009/09/05)
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- Pheromone synthesis. Part 240: Cross-metathesis with Grubbs I (but not Grubbs II) catalyst for the synthesis of (R)-trogodermal (14-methyl-8-hexadecenal) to study the optical rotatory powers of compounds with a terminal sec-butyl group
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(R)-Trogodermal (14-methyl-8-hexadecenal), the sex pheromone of Trogoderma species of pest insects against stored products, and its (S)-isomer were synthesized by using olefin cross-metathesis between (R)- or (S)-7-methyl-1-nonene and 8-nonenyl acetate as the key step. This step was successful with Grubbs I but not with Grubbs II catalyst. The latter caused randomization of the carbon skeleton to give a mixture of abnormal products with both longer or shorter carbon chains than the desired product. The specific rotations of 18 newly and 6 previously synthesized compounds with a terminal sec-butyl group were measured to conclude them to be [α]D +3.5 to +6.5 or -3.6 to -6.4.
- Mori, Kenji
-
experimental part
p. 3900 - 3909
(2009/09/08)
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- Photochromic glassy liquid crystals comprising mesogenic pendants to dithienylethene cores
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Photochromic glassy liquid crystals were synthesized using dithienylethenes as the volume-excluding cores to which liquid crystalline mesogens were chemically bonded through alkyl spacers. Nematic, smectic, and cholesteric glassy liquid crystals were demonstrated with glass transition temperatures above 90 °C and clearing points up to 220 °C without traces of crystallization on cooling or crystalline melting on heating. A monodomain cholesteric glassy liquid crystalline film containing an enantiomeric 2-methylpropylene chiral spacer was characterized as a left-handed helical stack, exhibiting a selective reflection band centered at 686 nm, an orientational order parameter of 0.65 for the quasi-nematic layers, and a combination of reflective coloration with photoswitchable absorptive coloration.
- Kim, Chunki,Marshall, Kenneth L.,Wallace, Jason U.,Chen, Shaw H.
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supporting information; experimental part
p. 5592 - 5598
(2010/03/03)
-
- First total synthesis and assignment of the absolute configuration of the neuronal cell protecting alkaloid carbazomadurin B
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Using a palladium-catalyzed approach, the first enantio-selective synthesis of the neuronal cell protecting agent carbazomadurin B is described and its absolute configuration is assigned. Georg Thieme Verlag Stuttgart.
- Kn?ll, Jan,Kn?lker, Hans-Joachim
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p. 651 - 653
(2007/10/03)
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- Identification and assignment of the absolute configuration of biologically active methyl-branched ketones from limnephilid caddis flies
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Glands of the 4th and 5th abdominal stemite of the caddis flies Potamophylax latipennis, Potamophylax cingulatus, and Glyphotaelius pellucidus contain (S)-4-methyl-3-heptanone (4a), (4S,6S)-4,6-dimethyl-3-octanone (4b), and (4S,6S)-4,6-dimethyl-3-nonanone (4c). As shown by gas chromatography coupled with electrophysiological recordings, these ketones elicit a strong response in the insects' antennae. The structural assignment of the compounds was achieved on the basis of mass spectra, enantioselective synthesis, and gas chromatography on a chiral stationary phase.
- Bergmann, Jan,Loefstedt, Christer,Ivanov, Vladimir D.,Francke, Wittko
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p. 3175 - 3179
(2007/10/03)
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- Synthesis and spectroscopic and electrochemical characterisation of a conducting polythiophene bearing a chiral β-substituent: Polymerisation of (+)-4,4′-bis[(S)-2-methylbutylsulfanyl]-2,2′-bithiophene
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A regioregular head-lo-head/ tail-to-tail poly(β,β′-disubstituted bithiophene) P1 was synthesised by chemical and electrochemical polymerisation of 2,2′-bithiophene that bears (S)-2-methylbutylsulfanyl chains in the β and β′-positions. The polymer was characterised by GPC, NMR and UV/Vis spectroscopy, CD, AFM and by electrochemical and conductivity measurements. The CD spectra of P1 in solutions in which poor solvents are present show interesting features and allow the presence of different optically active species to be distinguished. Upon varying the casting conditions of P1, different relative amounts of grainy and homogeneous aggregated phases were observed in AFM micrographies of films and corresponding negative or positive first Cotton effects were found in the CD spectra. AFM, CD and UV/Vis characterisations were also performed on an electrogenerated optically active polymer PE1, in order to make a comparison with the chemically synthesised one. The interesting, small band gap of P1 allows for easy p- and n-electrochemical doping. WILEY-VCH Verlag GmbH, 2001.
- Iarossi, Dario,Mucci, Adele,Parenti, Francesca,Schenetti, Luisa,Seeber, Renato,Zanardi, Chiara,Forni, Arrigo,Tonelli, Massimo
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p. 676 - 685
(2007/10/03)
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- Syntheses of the sixteen stereoisomers of 3,7,11-trimethyl-2-tridecanol, including the (2S,3S,7S,11R) and (2S,3S,7S,11S) stereoisomers identified as pheromone precursors in females of the pine sawfly Microdiprion pallipes (Hymenoptera: Diprionidae)
-
All sixteen stereoisomers of 3,7,11-trimethyl-2-tridecanol were synthesised in high stereoisomerical purities (> 95%), for use in the identification of the stereoisomers present in females of the pine sawfly Microdiprion pallipes (Fallén) (Hymenoptera: Diprionidae) as the precursor of the actual sex pheromone (which is the propionate), and also for investigation of the biological activities of the esters. The key step in the syntheses was the coupling of each of the enantiomers of cis-3,4-dimethyl-γ-butyrolactone with each of the four pure stereoisomers of 1-lithio-2,6-dimethyloctanes. The four corresponding alcohols were obtained by lipase-catalysed (Amano PS) kinetic separation, based on selective acylation of either (2R/S,6S)- or (2R/S,6R)-2,6-dimethyl-1-octanol (obtained from the optically pure enantiomers of citronellal). Additionally, a mixture of the 16 possible stereoisomers of 3,7,11-trimethyl-2-tridecanol was also prepared. Wiley-VCH Verlag GmbH, 2001.
- Larsson, Michael,Nguyen, Ba-Vu,H?gberg, Hans-Erik,Hedenstr?m, Erik
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p. 353 - 363
(2007/10/03)
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- Synthesis and biological activity of methyl 2,6,10-trimethyldodecanoate and methyl 2,6,10-trimethyltridecanoate: Male-produced sexual pheromones of stink bugs Euschistus heros and Piezodorus guildinii
-
Methyl 2,6,10-trimethyltridecanoate (1) and methyl 2,6,10-trimethyldodecanoate (2) have been identified as male-produced sex pheromones of the Brazilian soybean stink bugs Euschistus heros (F.) and Piezodorus guildinii (Westwood). In order to establish a defined attractive blend for both species, compounds 1 and 2 were synthesized as mixtures of stereoisomers to be employed in behavior bioassays. (±)-Citronellol (3) was utilized as starting material, and the syntheses was carried out in six steps with good overall yield. When tested alone, synthetic compounds 1 and 2 proved to be active in a two-choice olfactometer; however, a 20: 1 mixture of 1 and 2 was much more attractive to E. heros females. A similar blend had been found among the headspace volatiles of males.
- Zarbin, Paulo H. G.,Reckziegel, Aurelia,Plass, Ernst,Borges, Miguel,Francke, Wittko
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p. 2737 - 2746
(2007/10/03)
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- Esterification of carboxylic acid salts
-
Mono- or polycarboxylic acid esters are prepared by reacting a salt of such carboxylic acid with an organic halocompound, e.g., a (cyclo)alkyl, (cyclo)alkenyl, aryl or aralkyl halide, in an aqueous reaction medium, in the presence of a catalytically effective amount of a phase transfer catalyst, for example an onium salt.
- -
-
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- Hair cosmetic composition
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A hair cosmetic composition comprising a branched fatty acids of the following formula (1), STR1 wherein R1 is a methyl or ethyl group, n is an integer of 4-16, and R2 is an amino, alkoxy, or glycerol group. The composition imparts excellent sensation to hair and prevents hairs from being damaged.
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- 5. Novel alkaloids from the poison glands of ants Leptothoracini
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Novel pyrrolidine alkaloids were isolated from the poison glands of ants Leptothoracini (Myrmicinae) and identified as a mixture of N-alkylated 3-methylpyrrolidines. The females of these species produce male-attracting pheromones in their poison glands. The basic compounds in the secretions were found to be active. The major alkaloid, 3-methyl-1-(3-methylbutyl)pyrrolidine (5), is present in only ng quantities per gland.
- Reder,Veith,Buschinger
-
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- Variation of the Alkyl Side Chain in Δ8-THC
-
The synthesis of (2'RS)-2'-methyl-, (3'RS)-, (3'S)-3'-methyl-, and 4'-methyl-Δ8-THC has been carried out, and the pharmacology of all four compounds has been investigated. All four compounds showed typical cannabinoid activity both in vitro and in vivo. The 2'-methyl compound is somewhat more active than Δ8-THC, while the 4'-methyl isomer is less active. The 3'-methyl-Δ8-THC has approximately the same activity as the parent cannabinoid.
- Huffman, John W.,Lainton, Julia A. H.,Dai, Dong,Jordan, Robert D.,Duncan, Sammy G.
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p. 2021 - 2024
(2007/10/03)
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- Synthesis, Absolute Configuration, Spectroscopic and Chiroptical Properties of Chiral Dinuclear Tri- and Pentamethinium as well as Trinuclear Heptamethinediium Cyanine Dyes with 3-sec-Butyl-1,3-dimethylindolyl End Groups
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Starting with natural monochiral (-)-(S)-2-methyl-1-butanol (1a) generated by alcoholic fermentations, we have synthesized the new monochiral heterocyclic iminium salt (+)-(3R,15S)-3-sec-butyl-1,2,3-trimethylindoleninium tetrafluoroborate (11) in an eight-step reaction sequence.Important steps of this sequence are the zeolite-catalyzed Fischer synthesis of the monochiral indole 6a from the phenylhydrazone of ketone 5a and the separation of the diastereomeric salts 9 and 10 by fourfold fractional recrystallization from ethanol.With the new quaternary iminium salt 11, new monochiral dinuclear tri- (13) and pentamethinium cyanine dyes (14) as well as the trinuclear heptamethinediium 17 and tetramethinium cyanine dyes 18 have been synthesized.The absolute configuration of the four stereogenic centers in the cyanine dye 14 has been confirmed by means of an X-ray structural analysis.Spectroscopical and chiroptical properties of all new cyanine dyes have been determined. - Key Words: Cyanine dyes, chiral/ Dyes/ Heptamethinediium cyanine dyes, chiral/ Pentamethinium cyanine dyes, chiral/ Polymethine cyanine dyes, chiral/ Trimethinium cyanine dyes, chiral
- Reichardt, Christian,Budnik, Ulrich,Harms, Klaus,Schaefer, Gerhard,Stein, Joerg
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p. 329 - 340
(2007/10/02)
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- Pheromones, 89.- Wittig Syntheses of Alkyl-Branched and Cyclic Analogs of (Z)-5-Decenyl Acetate, the Sex Pheromone of Agrotis segetum (Lepitoptera: Noctuidae)
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By means of (Z)-selective Wittig olefination alkyl-branched and cyclic analogs of (Z)-5-decenyl acetate, the sex pheromone of the turnip moth, Agrotis segetum (Lepidoptera: Noctuidae), have been synthesized. Key Words: Pheromones / (Z)-5-decenyl acetate / Wittig reactions / Agrotis segetum
- Albores, Martha,Bestmann, Hans Juergen,Doehla, Bodo,Hirsch, Hans-Ludwig,Roesel, Peter,Vostrowsky, Otto
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p. 231 - 236
(2007/10/02)
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- OZONOLYSIS OF ALKENES AND REACTIONS OF POLYFUNCTIONAL COMPOUNDS. XLVI. SYNTHESIS OF (4S,8S)-4,8-DIMETHYLDECANAL AND ITS DIMETHYL ACETAL
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From accessible chiral structural blocks, namely, (R)-methyl-citronellate and (S)-2-methyl-1-butanol, (6S,10S)-2,6,10-trimethyl-2-dodecene was synthesized.The ozonolysis of this gave (4S,8S)-4,8-dimethyldecanal, one of the stereoisomers of the aggregation pheromone of the meal worms Tribolium confusium and T. castaneum, and its dimethyl acetal.
- Odinokov, V. N.,Akhmetova, V. R.,Khasanov, Kh. D.,Abduvakhabov, A. A.,Sul'tanmuratova, V. R.,Tolsikov, G. A.
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p. 915 - 918
(2007/10/02)
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- Ethyl phenylsulfinyl fluoroacetate, a new and versatile reagent for the preparation of α-fluoro-α,β-unsaturated carboxylic acid esters
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The title compound 2 can be alkylated with a wide range of alkyl halides and Michael acceptors. Subsequent thermal elimination of phenyl sulfinic acid 3 leads to α-fluoro-α,β-unsaturated ethyl carboxylates 5 and 10, an important class of intermediates for fluorine containing biologically active compounds.
- Allmendinger, Thomas
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p. 4905 - 4914
(2007/10/02)
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- Pheromone Synthesis, CXXX. Synthesis of (4S,8S)- and (4S,8R)-4,8-Dimethyldecanal, the Stereoisomers of the Aggregation Pheromone of Tribolium castaneum
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(4S,8S)- and (4S,8R)-4,8-Dimethyldecanal (1) were synthesized by starting from (R)-citronellic acid (2a), methyl (S)-3-hydroxyy-2-methylpropanoate (3a), and (S)-2-methyl-1-butanol (4a).
- Mori, Kenji,Takikawa, Hirosato
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p. 497 - 500
(2007/10/02)
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- Synthesis and Properties of Optically Active (+)-p'-2-methyl-butoxyphenyl p-(p"-alkoxybenzoyloxy)-benzoates
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Ten compounds of the title series represented by (d)AmPABOB were synthesized and their mesomorphic properties evaluated by DSC and optical microscopy.All the compounds have liquid crystal phases and three out of ten have a smectic C* phase.Measurements of the molecular tilt angle and the pitch were presented.Investigation on textures of mesophases revealed some anomalous phenomena.
- Dong, C. C.,Sun, Z. M.,Li, G. Z.
-
-
- Pyridinium N-Phenoxide Betaines and Their Application for the Characterization of Solvent Polarities, XIV. - Attempted Synthesis of a Chiro-Solvatochromic Pyridinium N-Phenoxide Betaine Dye
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Synthesis and UV/VIS spectroscopic properties of the negatively solvatochromic, chiral, (S,S)-configurated betaine dye 8 are described.There is a linear correlation between the E'T values of 8 and the ET(30) values of the standard betaine dye 1 (Figure 1).Unfortunately, (S,S)-8, dissolved in enantiomeric pure (R)- and (S)-configurated alcohols and amines, does not show a measurable chiro-sovatochromism (Table 2).
- Reichardt, Christian,Wilk, Martina
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p. 189 - 194
(2007/10/02)
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- Syntheses with Aliphatic Dialdehydes, XLIV. Chiral Pentamethine Cyanine Dyes and Heterocycles from Derivatives of (S)-(+)-2-sec-Butylmalonaldehyde
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Syntheses and UV/Vis-spectroscopic properties of the chain-substituted, homochiral pentamethine cyanine dyes 16 and 17 are described. 16 and 17 as well as the homochiral five-, six-, and seven-membered heterocycles 11 - 15 are prepared from derivatives (5 and 6) of homochiral (S)-(+)-2-sec-Butylmalonaldehyde (8), the first known chiral malonaldehyde, which in turn is synthesized in a seven-step procedure from homochiral (S)-(-)-2-methyl-1-butanol (1).
- Reichardt, Christian,Budnik, Ulrich
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p. 2023 - 2030
(2007/10/02)
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- A Comprehensive Approach to (S)-(-)-2-Methyl-1-Butanol as a Convenient Precursor for Synthesis of Chiral Liquid Crystals
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The chemistry of S-(-)-2-methyl-1-butanol leading to chiral liquid crystals (CLC) and their intermediates is summarized and new facile synthetic methods are described.Efficiency of the presented methods is discussed and illustrated with syntheses of several known and new CLC as well as the corresponding chiral intermediates.The newly synthesized chiral compounds display cholestic and smectic phases.Keywords: (S)-(-)-2-methyl-1-butanol, (S)-(+)-methyl-1-butyl benzenesulfonate, chiral liquid crystals, smectic C
- Kaszynski, P.,Jawdosiuk, M.
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- Pheromones, 67. - Synthesis of the Enantiomers of (Z)-14-Methyl-8-hexadecenal , the Pheromone of Some Trogoderma Species (Coleoptera: Dermestidae)
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The separation of diastereomeric phenylglycinolamides of 2-methylbutyric acid by means of MPLC yields the pure enantiomers of the acid, from which (R,Z)- and (S,Z)-14-methyl-8-hexadecenal (1) (trogodermal) can be obtained.
- Bestmann, Hans Juergen,Frighetto, Rosa T. S.,Frighetto, Nelson,Vostrowsky, Otto
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p. 877 - 880
(2007/10/02)
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- Synthesis of the chiral components of the sex pheromone of Adoxophyes leaf roller moths
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The optically pure (R) and (S) enantiomers of 10-methyldodecyl acetate were synthesized from (R)-5-acetoxy-4-methylpentanoic acid and (S)-2-methylbutanol, respectively, using the condensation of (R)- and (S)-2-methylbutylmagnesium bromides with 8-tosyloxyoctyl acetate in the presence of Li2CuCl4 in the key step.
- Cheskis, B. A.,Moiseenkov, A. M.
-
-
- 48. Ferroelectric Liquid Crystals Part 2 Chiral Phenyl Benzoates Incorporating a trans-1,4-Disubstituted Cyclohexane Ring
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About forty novel phenyl benzoates also incorporating a trans-1,4-disubstituted cyclohexane ring and a chiral centre have been prepared.The dependence of the liquid-crystal transition temperatures of this new class of compounds on lateral substituents, diverse central linkages, chain lengths, and position of the chiral centre has been studied systematically.The synthesis and liquid-crystal transition temperatures of these new compounds are described in detail.
- Kelly, Stephen M.,Buchecker, Richard
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p. 451 - 460
(2007/10/02)
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- Towards Chiral Metals. Synthesis of Chiral Conducting Polymers from Optically Active Thiophene and Pyrrole Derivatives
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The synthesis of free standing and clay-supported chiral conducting polymer films is described.
- Kotkar, Dilip,Joshi, Vishwas,Ghosh, Pushpito K.
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p. 917 - 918
(2007/10/02)
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- PREPARATION OF (S)-2-METHYLBUTYLAMINE AND SYNTHESIS OF CHIRAL ISOLEUCINE AND alloISOLEUCINE.
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A four-step synthesis (45 percent total yield) of a mixture of chiral pure L-isoleucine and D-alloisoleucine is reported, via a route comprising an anodic oxidation of suitable acylamide precursors.Efficient preparations for (S)-2-methylbutylamine from the cheap parent (S)-alcohol are described.
- Anteunis, M. J. O.,Callens, R.,Witte, M. De,Reyniers, M. F.,Spiessens, L.
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p. 545 - 554
(2007/10/02)
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- ENANTIOSELECTIVE CATALYSIS, 34 PHOSPHINES WITH (S)-2-METHYLBUTYL SUBSTITUENTS AND THEIR Rh COMPLEXES - USE IN ENANTIOSELECTIVE CATALYSIS
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(S)-2-methylbutyl Grignard, prepared from (S)-(-)-2-methylbutan-1-ol via (S)-(+)-2-methylbutyl-1-bromide, was used for the synthesis of phosphines 1-4, containing (S)-2-methylbutyl substituents.In the reaction with 2, phosphines 1 and 2 give the neutral complexes 5 and 6 of the type Rh(cod)(L)Cl, whereas phosphines 3 and 4 give the salts 7 and 8 of the type PF6.The isolated complexes 5-8 and the in situ systems 2/1-4 lead to optical inductions of up to 15 percent ee in the enantioselective hydrosilylation of acetophenone with diphenylsilane.
- Brunner, H.,Leyerer, H.
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p. 353 - 360
(2007/10/02)
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- Conformational Analysis and Stereodynamics of Primary Acyclic Alkyl Radicals by EPR Spectroscopy
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The EPR spectra of n-alkyl, 2-methylalkyl, 2,2-dimethylalkyl, 2,2,3-trimethylbutyl, and 2,2,3,3-tetramethylbutyl radicals indicate that at 90 K they exist in "rigid" conformations with respect to rotation about the Cβ-Cγ bonds.The preferred conformations about the Cα-Cβ and Cβ-Cγ bonds were deduced by analysis of the β- and γ-H hyperfine splittings (hfs). 2,2,3,3-Tetramethylbutyl radicals, the only radicals with a CH3 group approximately all-trans with respect to the semioccupied p-orbital, were also the only radicals to show resolved δ-hfs.The barriers to internal rotation of the methyl groups in n-propyl, isobutyl, neopentyl, 2,2-bis(trideuteriomethyl)butyl, and 2,2,3,3-tetramethylbutyl radicals were obtained by line shape analysis; the ethyl rotation barrier in 2,2-bis(trideuteriomethyl)butyl and the tert-butyl rotation barrier in 2,2,3,3-tetramethylbutyl radicals were estimated in a similar way.The experimental hfs of trans γ-hydrogens were shown to fit a relationship of the form aHγ = 0.1 +7.9 cos2 Φ, where Φ is the dihedral angle between the SOMO and the plane through Cα, Cβ, and Cγ.Trends in the internal rotation barriers of the alkyl groups were adequately accounted for in terms of steric effects.
- Ingold, K. U.,Nonhebel, D. C.,Walton, J. C.
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p. 2859 - 2869
(2007/10/02)
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- Silylaminyl Radicals. Part 2. Free Radical Chain Halogenation of Hydrocarbons using N-Halogenobis(trialkylsilyl)amines
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The liquid-phase halogenation of a number of hydrocarbons and of 1-chlorobutane by N-halogenobis(trialkylsilyl)amines has been studied using product analysis techniques.The reactions take place by free radical chain mechanisms which involve the propagation steps generalised in equations (A) and (B) (X=Br or Cl).At 353 K, the molar reactivities of toluene (benzylic C-H) and cyclohexane towards (R3Si)2N+RH(R3Si)2NH+R (A) R+(R3Si)2NXRX+(R3Si)2N (B) (Me3Si)2N are approximately equal and toluene is 5.2 times more reactive than perdeuteriotoluene.The relative rates of hydrogen abstraction by (Me3Si)2N and (ButMe2Si)2N from the primary, secondary, and tertiary C-H groups in 2-methylbutane show that the silylaminyl radicals are not only highly reactive but also sterically demanding.Thus, at 333 K the average primary C-H reactivity is 0.6 times that of the tertiary C-H towards attack by (Me3Si)2N, but 4.2 times that of the tertiary C-H towards attack by the more bulky (ButMe2Si)2N.Silylaminyl radicals are much more reactive in hydrogen abstraction than are analogous dialkylaminyl radicals and this difference is interpreted in terms of thermodynamic and polar effects which arise because of the ?-donor-?-acceptor nature of the trialkylsilyl substituent.
- Cook, Malcolm D.,Roberts, Brian P.,Singh, Karamjit
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p. 635 - 644
(2007/10/02)
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- Reaction of Grignard Reagents with Benzaldehyde, 2,2-Dimethylpropanal and Cinnamates of Chiral Alcohols in Chiral Solvents
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The asymmetric induction in a Grignard reaction carried out in (-)-1-isopropyl-2-methoxy-4-methylcyclohexane was higher than in the reaction carried out in (+)-1-methoxy-2-methylbutane.The chirality of the solvent contributed more than that of the reagent stereodifferentiation in the reaction of (+)-2-methylbutylmagnesium bromide with benzaldehyde in (+)-1-methoxy-2-methylbutane.
- Jalander, Lars,Strandberg, Rolf
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- Synthesis of Optically Active Aggregation Pheromone Analogues of the Red Flour Beetle, Tribolium castaneum
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Seven optically active analogues which were (4S)-, (8S)- and (4R)-analogues of the aggregation pheromone of the red flour beetle, Tribolium castaneum, were stereoselectively synthesized from optically pure (R)-(+)-citronellic acid (100percent e.e.) and/or (S)-(-)-2-methyl-1-butanol (93percent e.e.) to elucidate the structure-activity relationship of the pheromone.The (8S)-configuration was derived from (S)-(-)-2-methyl-1-butanol, and the (4S)- or (4R)-configuration was from (R)-(+)-citronellic acid.
- Suzuki, Takahisa,Ozaki, Jotaro,Sugawara, Ryozo
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p. 869 - 876
(2007/10/02)
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- Isomerization of Alkane Molecular Ions
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The appearance energies of daughter ions for the major low-energy fragmentations, namely, losses of C2H6, CH4, and CH3*, of pentane and methylbutane radical cations have been measured.These reactions for ions of low internal energy content (rate constants in the range 1E5 - 1E7 s-1) have been studied by observations of metastable peak shapes.The behaviors of a variety of 13C- and 2H-labeled compounds were also examined.Hydrogen atoms do not extensively lose their positional identity in any of these fragmentations.For methylbutane, loss of C2H6 and CH3* yielded ionized propene and 2-butyl cations, respectively, at their calculated thermochemical thresholds.Loss of CH4 proceeded at an energy greater than that calculated for the production of ionized but-2-ene, methylpropene, but-1-ene, or methylcyclopropane.The labeling experiments permitted the separation of the complex Gaussian-type metastable peak for CH4 loss into high and low kinetic energy release components, each appropriately relating to the generation of different daughter ions via competing mechanistic pathways.Large isotope effects were observed, similar in magnitude to those observed for the loss of methane from the methylpropane radical cation.Ethane elimination is preceded partially (ca. 20-25percent) by a 1-2 methyl shift and a concominant 2-1 H shift; isotope effects associated with this reaction are discussed. for pentane, losses of CH3* and CH4 take place at the same energy, corresponding to the calculated threshold for production of the secondary cations; 13C labeling experiments showed that the penultimate C atoms are not lost but that C-3 is lost (46percent) in these reactions, with an ease similar to terminal C atom losses (54percent).As with methylbutane, 2H labeling permitted the separation of the metastable peak for methane loss into components having different kinetic energy releases and attributable to the production of different (+*) daughter ions.Although C2H6 loss was observed to take place at energies down to the calculated thermochemical threshold for generation of ionized propene, the appearance energy of the metastable peak was the same as that for CH3* and CH4 losses.Labeling experiments showed that the central C atom is not lost in this reaction.Detailed analysis of the observations leads to the conclusion that the CH3*, CH4, and C2H6 eliminations from pentane radical cations are preceded by an isomerization to energy-rich ionized methylbutane.
- Holmes, John L.,Burgers, Peter C.,Mollah, M. Yousuf A.,Wolkoff, Peder
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p. 2879 - 2884
(2007/10/02)
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- Liquid crystal compounds
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Novel liquid crystal compounds are disclosed, which are chiral esters based upon the phenol STR1 Typical examples are: STR2 and mixtures of these compounds have a helical pitch such that the mixtures reflect light of a specific wavelength when illuminated with ordinary light and the pitch is temperature sensitive so that the mixtures can be used in temperature indicating devices. Specific examples are given as are samples of mixtures that can be used in phase change electro-optic display devices.
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- Optically Active Thiolesters from S-(+)-3-Methylcarproic Acid by Arndt-Eistert Synthesis
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For the first time Arndt-Eistert synthesis the thiolesters are prepared using mercaptans.The various alkyl mercaptans react with diazoketone prepared from S-(+)-3-methylcaproyl chloride yield a series of higher homologous optically active thiolesters of the type, CH3CH2CH*(CH3)CH2CH2CH2COSR, where R=n-propyl, isopropyl, n-butyl, n-amyl, n-hexyl, n-heptyl and n-octyl.The optical rotation and infrared spectra of these thiolesters have been studied.
- Vasi, I. G.,Nanavati, N. T.
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p. 744 - 745
(2007/10/02)
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