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  • 1
    Electronic Resource
    Electronic Resource
    Preparative scale enantioseparation of a chiral epoxide: Comparison of liquid chromatography and simulated moving bed adsorption technology (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 267-271 
    Details
    ISSN: 0899-0042
    Keywords: simulated moving bed technology ; chiral separation ; cellulose triacetate ; preparative scale liquid chromatography ; racemic epoxide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The feasibility of using simulated moving bed technology (SMB) for chiral separation on cellulose triacetate is demonstrated on the preparative scale: 1 kg of a chiral epoxide has been separated. On comparing SMB technology with conventional liquid chromatography it turns out that the main advantage of SMB lies in the significant reduction of mobile phase consumption. The process design for SMB is made theoretically and the predictions are confirmed by our pilot study. © 1993 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050415
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of Enantiomerically Pure D- and L-(Heteroaryl)alanines by asymmetric hydrogenation of (Z)-α-amino-αβ-didehydro esters (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1395-1411 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homogeneous asymmetric hydrogenation of a wide range of methyl and tert-butyl (Z)-2-(acylamino)-3-(heteroaryl)acrylates (see 1a-f and 2a-d, f, g, resp.) catalyzed by diphosphinerhodium catalysts was studied for the synthesis of enantiomerically pure 3-furyl-, 3-thienyl-, and 3-pyrrolylalanines (see 3a-f, and 4a-d, g; Scheme 1). The precursors, the (Z)-α-amino-α,β-didehydro esters 1a-f and 2a-d, f, g were prepared in high yields using the phosphorylglycine-ester method (Scheme 1). Isomerically pure (Z)-α-amino-α,β-didehydro esters were required to obtain the highest enantiomeric excesses (ee's) in the asymmetric hydrogenation, and the tert-butyl-ester strategy was beneficial in terms of both getting pure (Z)-α-amino-α,β-didehydro esters and obtaining high ee's in the hydrogenation. Finally, in contrast to the methyl-ester series, deprotection of the tert-butyl esters 4a-d, g was easily performed using CF3CO2H without any racemization.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770518
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  • 3
    Electronic Resource
    Electronic Resource
    (2R,4R,6R,8R)-2,4,6,8-Tetramethyldecan- und -undecansäure aus dem Bürzeldrüsenwachs der Hausgans, Anser a. f. domesticus: Isolierung, Synthese einiger Derivate sowie der rac-2,4,6,8-Tetramethyldecansäure (1992)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 433-439 
    Details
    ISSN: 0170-2041
    Keywords: Fatty acids ; Anser a.f. domesticus ; Waxes ; Preen-gland ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (2R,4R,6R,8R)-2,4,6,8-Tetramethyldecanoic- and -undecanoic Acid of the Preen-gland Wax from the Domestic Goose, Anser a.f. domesticus: Isolation, Synthesis of Derivatives and of the rac-2,4,6,8-Tetramethyldecanoic AcidLarge quantities of (2R,4R,6R,8R)-2,4,6,8-tetramethyldecanoic- and -undecanoic acid methyl ester (3 and 4) were obtained after transesterification and Spaltrohr® distillation of the preen-gland wax of the domestic goose. Hydrolysis with NaOH/dioxan afforded the acids 5 and 6. Reduction of 3 with LiAlH4 gave (2R,4R,6R,8R)-2,4,6,8-tetramethyldecanol (7). Esterification of 5 and 6 with octadecanol yielded the pure wax esters 1 and 2, while 5 with glycerol gave the triglyceride 9 and 5 with 7 afforded 8. Alcohol 7 and octadecyl bromide, in the presence of NaH/DMF, afforded the ether 10. The racemic acid 22, corresponding to 5, was obtained synthetically by starting with a modified Wittig reaction of 2-(diethoxyphosphoryl)propionic acid ethyl ester on 2-methylbutyraldehyde. Transesterification of the ethyl ester 21 with octadecanol gave the racemic wax ester 23, corresponding to 1. The optical activity and 13C data of the compounds are reported.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199219920179
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  • 4
    Electronic Resource
    Electronic Resource
    Chemo-enzymatische Synthese von Kohlenhydraten: Die Herstellung von L-Xylose und 2-Desoxy-L-xylo-hexose (1992)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 95-97 
    Details
    ISSN: 0170-2041
    Keywords: L-Xylose ; 2-Deoxy-L-xylo-hexose ; Enzymatic syntheses ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemo-Enzymatic Synthesis of Carbohydrates: The Preparation of L-Xylose and 2-Deoxy-L-xylo-hexoseA synthetic approach to L-xylose (6) and 2-deoxy-L-xylo-hexose (8) has been developed. The strategy utilizes achiral starting materials and employs two enzymatic reactions to introduce the desired chiral centers. Rabbit muscle aldolase (RAMA)-catalyzed condensation of (3-phenylthio)propanal (1) with dihydroxyacetone phosphate (DHAP) affords the C-6 skeleton 2 with D-threo configuration between C-3 and C-4. Diastereoselective reduction of 2 with sorbitol dehydrogenase (SDH) introduces the final stereocenter of the tetrahydroxy derivative 3. After oxidation of sulfide 3 to the corresponding diastereotopic sulfoxides 4, L-xylose (6) is obtained by thermal elimination of phenylsulfenic acid followed by ozonolysis. 2-Deoxy-L-xylo-hexose (8) is yielded from 4 by a Pummerer rearrangement and subsequent reductive deprotection (DI-BAL-H) of the rearrangement product 7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199219920119
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  • 5
    Electronic Resource
    Electronic Resource
    Structural variations of N-acetylneuraminic acid, 18. Synthesis of the side chain stereo and deoxy analogs of 5-acetamido-2,6-anhydro-3,5-dideoxy-D-erythro-L-manno-nononic acid (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 1185-1195 
    Details
    ISSN: 0170-2041
    Keywords: Sialic acids ; Hemagglutinin inhibitors ; N-Acetylneuraminic acid, deoxygenation and epimerization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 5-acetamido-2,6-anhydro-3,5-dideoxy-D- erythro-L-manno-nonic acid (3b, 7,8-epi2-2-d-2-HeqNeu5Ac) and sodium 5-acetamido-2,6-anhydro-3,5-dideoxy-L-threo-L-manno-nonate (6b, 8-epi-2-d-2-Heq-Neu5Ac) could be realized by transformation of 5-acetamido-3,5-dideoxy-L-glycero-L-altro-2-nonulopyranosonic acid (2a, 7,8-bis-epi-Neu5Ac) and 5-acetamido-3,5-dideoxy-3-L-glycero-D-galacto-2-nonulosonic acid (5a, 8-epi-Neu5Ac) into the corresponding peracetylated 2-chloro derivatives and subsequent catalytic hydrogenation. As this procedure could not be applied to the synthesis of the 7-epi, 7-deoxy and 8-deoxy derivatives a new strategy, which started with the methyl 5-acetamido-2,6-anhydro-3,5-dideoxy-D-erythro-L-manno-nonoate (1e), was designed. For this purpose, a gram-scale preparation of 1e was developed. Transformation of protecting groups and radical reduction of selectively introduced tolylthiocarbonate groups led to the corresponding 5-acetamido-2,6-anhydro-3,5,7-trideoxy-D-glycero-L-manno-nonoic acid (12b, 2,7-d2-2Heq-Neu5Ac) and sodium 5-acetamido-2,6-anhydro-3,5,8-trideoxy-D-glycero-L-manno-nonate (11b, 2,8-d2-2Heq-Neu5Ac). An oxidation  -  reduction sequence yielded 5-acetamido-2,6-anhydro-3,5-dideoxy-D-threo-L-manno-nonoic acid (9c, 2d-2Heq-7-epi-Neu5Ac). Also the sialic acid analog 6b could be prepared according to this newly designed strategy.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1990199001216
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  • 6
    Electronic Resource
    Electronic Resource
    Indium-assisted allylation in carbohydrate chemistry: A convenient route to D-glycero-D-galacto- and D-glycero-L-galacto-heptose (1994)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 73-78 
    Details
    ISSN: 0170-2041
    Keywords: Allylation, indium-assisted ; Aldoheptoses ; Catalytic osmylation ; Indium-assisted allylation ; Carbohydrates ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting with unprotected D-pentoses 1-4 we achieved a chain elongation reaction by utilizing indium-assisted allylation. After acetylation, the polyol derivatives 1a-4a were transformed into the corresponding α,β-unsaturated aldehydes 1b-4b. Protection of the carbonyl group yielded the diethyl acetals 1c-4c. Subsequent dihydroxylation of the double bond by catalytic osmylation followed by acetylation of the newly introduced hydroxyl functions gave a mixture of diastereomeric products. However, only those diastereomers could be easily separated by column chromatography which were derived from 1c and 2c, giving access to D-glycero-D-galacto and D-glycero-L-galacto precursor 5 and 7, respectively. Final deprotection yielded the title aldoheptoses 6 and 8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199419940113
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  • 7
    Electronic Resource
    Electronic Resource
    Chromatographische Trennung und quantitative Bestimmung aller acht Stereoisomeren von α-TocopherolHerrn Dr. Otto Isler zum 80. Geburtstag gewidmet (1990)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 73 (1990), S. 782-789 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Separation and Quantitation of All Eight Stereoisomers of α-Tocopherol by ChromatographyThe results of the analysis of several derivatives of (all-rac)-α-tocopherol by HPLC on a chiral stationary phase and by capillary GC on a achiral stationary phase are reported. Consecutive application of both methods to the ethyl-ether derivative allows the separation and quantification of all eight possible stereoisomers of (all-rac)-α-tocopherol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19900730403
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis of Optically Active Bifunctional Isoprenoid Building Blocks by Rhodium(I)-Catalyzed Asymmetric Allylamine to Enamine IsomerizationPresented in part at the ‘6th International Symposium on Homogeneous Catalysis’, Vancouver, Canada, August 21-26, 1998.Dedicated to Dr. Otto Isler on the occasion of his 80th birthday (1990)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 73 (1990), S. 1258-1275 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of the known asymmetric allylamine to enamine isomerization methodology to bifunctional C5-isoprenoid allylic amines of types IId and IIe (Scheme 1) is described. It is shown that a number of such substrates can be isomerized with enantioselectivities of 〉 90% ee. using cationie Rh1 complexes containing (6. 6′-dimethylbiphenyl′2, 2′-diyl)bis(dipheny phosphine) (BIPHEMP; 9) as asymmetry-inducing ligand (Scheme 2, Tables 1 and 2). Synthetically most useful is the isomerization of the benzyloxy derivative 10a into the (E)-enamine 11a. This isomerization proceeds with very high enantioselectivity (98-99% ee) and affords, after enamine hydrolysis, the optically active 4-(benzyloxy)-3-methylbutanals ((R)- or (S)-12) in chemical yields of ca. 90%. In conjunction, a short synthetic route to the starting material 10a has been developed which has a Pd-catalyzed amination of isoprene epoxide (30) as the key step. Thus, convenient and practical access to the optically active aldehydes (R)-and (S)-12 is now at hand. These aldehydes are useful optically active bifunctional building blocks for isoprenoid homologation.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19900730516
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  • 9
    Electronic Resource
    Electronic Resource
    Axially Dissymmetric Diphosphines in the Biphenyl Series: Synthesis of (6,6′-Dimethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine)(‘MeO-BIPHEP’) and Analogues via an ortho-Lithiation/Iodination Ullmann-Reaction Approach (1991)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 370-389 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new axially dissymmetric diphosphines (R)- and (S)-(6,6′-dimethoxybiphenyl-2,2′-diyl)bis(diphenyl phosphine) ((R)- and (S)-5a; ‘MeO-BIPHEP’) and the analogues (R)- and (S)-5b and 5c have been synthesized in enantiomerically pure form. These ligands have become readily available by a synthetic scheme which employs, as key steps, an ortho-lithiation/iodination reaction of the (m-methoxyphenyl)diprienylphosphine oxides 8 and a subsequent Ullmann reaction of the resulting iodides 9 to provide the racemic bis(phosphine oxides) 10. The bis(phosphine oxides) 10 subsequently are resolved with (-)-(2R,3R)- and (+)-(2S,3S)-O-2,3-dibenzoyltartaric acid and reduced to diphosphines 5. The Ullmann reaction constitutes a new and efficient route to 2,2′-bis(phosphinoyl)-substituted biphenyl systems. Absolute configurations were established for (R)-5a by X-ray analysis of the derived Pd complex (R,R)-17a, and for 5b and 5c by means of 1H-NMR comparisons of the derived Pd complexes 16 or 17, respectively, and by means of CD comparisons. The MeO-BIPHEP diphosphine 5a proved to be as efficient as the previously described BIPHEMP diphosphine ((6,6′-dimethylbiphenyl-2,2′-diyl)bis(diphenylphosphine)) in enantioselective isomerizations and hydrogenations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19910740215
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of All Four Stereoisomers of (E)-Vitamin KT (Phylloquinone), Analysis of Their Diastereoisomeric and Enantiomeric Purities and Determination of Their BiopotenciesPresented in part at the ‘6th International Symposium on Homogeneous Catalysis’, Vancouver, Canada, August 21-26, 1988.Dedicated to Dr. Otto Isler on the occasion of his 80th birthday (1990)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 73 (1990), S. 1276-1299 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: All four stereoisomers of (E)-vitamin Kb i. e. (21E, 7R, 111R)-l (= 1a), (21E, 71 R, l11S)-1 (= 1b), (21E, 71 S, 111S) 1 ( = 1c), and (21E, 71S, 111R)-l ( = Id), have been synthesized in a state of high chemical and stereoisomeric purity. The synthesis of stereoisomers lb-d relied on the use of the optically active Cf1* and C*10-building blocks (R)- or (S)-4-(benzyloxy)-3-methylbutanal ((R)- or (S)-2) and (R)- or (S)-citronellal ((R)- or (S)-3) which had been secured by the Rh1-catalyzed allylamine-to-enamine isomerization technology. For the synthesis of the natural (E)-vitamin-K1 stereoisomer 1a, a new route starting from natural phylol was developed, based on an O-alkylation/rearrangement procedure. A HPLC method was developed which separates with remarkable efficiency all four stereoisomers of (E)- as well as three out of the four stereoisomers of (Z)-vitamin K1 on optically active poly(trityl methacrylate) as the chiral stationary phase supported on Nucleosil. By this method, the stereoisomeric content of the stereoisomers 1b-d synthesized was shown to be in the range of 96-98 %, while the natural isomer 1a was configurationally uniform. The biological activity of the four (E)-vitamin-K1 stereoisomers was determined by means of the curative prothrombin time test with vitamin-K-depleted chicks. A high precision of the results was obtained with the recently introduced up-and-down organization of the test and the statistical evaluation according to an estimation procedure. With the natural (E)-vitamin-K1 stereoisomer 1a as standard (set at 1. 0), activities of 0. 93, 1. 19, and 0. 99 were found for stereoisomers 1b, 1c, and 1d, respectively. Within the confidence limits, these activity ratios can be regarded as identical, A very similar efficacy was obtained by comparison of (E, all-rac )-vitamin K1 ((21E, RS, 11′ RS)-1; equimolar mixture of the four stereoisomers 1a-d) with the natural (E)-vitamin-K1 stereoisomer 1a). A synergistic effect was not detectable, as was the case with the eight α-tocopheryl-acetate stereoisomers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19900730517
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