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  • 1
    Electronic Resource
    Electronic Resource
    The Molecular and Crystal Structure of the Glycopeptide A-40926 Aglycone (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 1916-1924 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a glycopeptide antibiotic A-40926 aglycone was investigated by X-ray analysis at -120°. A-40926 crystallises in the orthorhombic space group P212121 with two monomers in the asymmetric unit, a = 21.774(4), b = 28.603(7), c = 29.757(4) Å. ‘Conventional’ direct methods approach failed to solve the structure, but a novel iterative real/reciprocal space procedure was successful. Refinement against 11248 F2 data led to R1 = 13.3% for 6770 F 〉 4σ (F). The two monomers of A-40926 have similar conformations and are bound by antiparallel H-bonds to form a ‘chain’ structure of connecting dimers. The antibiotic molecule possesses a ‘binding pocket’ for the C-terminal carboxy group of the cell-wall protein, which is consisten with suggestions based on NMR data and the recently reported crystal structure of ureido-balhimycin. In A-40926 the monomers are polymerically linked by H-bonds, quite unlike the tight dimer formation observed in ureido-balhimycin.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790714
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  • 2
    Electronic Resource
    Electronic Resource
    Conformational Analysis of Didemnins. A multidisciplinary approach by means of X-Ray, NMR, molecular-dynamics, and molecular-mechanics techniques (1989)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 530-555 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present the application of several homo- and heteronuclear 1D- and 2D-NMR techniques to assign the 1H-NMR chemical shifts of the dominant conformation of didemnin B (2; three different conformations in (D6)DMSO solution in the ratio 8:1:1) and its conformational analysis, as well as the solution conformation of didemnin A (1). The conformations were refined by restrained molecular-dynamics calculations using the GROMOS program and by MOMO, a novel personal-computer-based interactive molecular-graphics and molecular-mechanics package, using experimental distances (via a H…H pseudo potential function) as restraints. The solution structures of 1 and 2 obtained by GROMOS and MOMO calculations were compared with each other and related to the recently solved crystal structure of 2. Focusing on the main conformer, the two kinds of the distance-restrained conformational calculations for 2 yielded a ‘solution structure’ close to the crystal structure. Almost all of the 40 restrained H…H distances coincided (within the estimated standard deviations) with those observed in the crystal structure. One more hydrogen bond was detected in solution involving the lactoyl OH group (disordered in the crystal structure) and the dimethyltyrosine (Me2Tyr5) carbonyl O-atom. The macrocyclic ring system in the modeled solution structure of 1 exhibited a topology close to those of the solution and crystal structures of 2. The main difference between 1 and 2 could be traced back to a significant change in the Ψ angle of the N-methyl-D-leucine (MeLeu7) residue. In 1, the N-methyl moiety of MeLeu7 points inward within the macrocyclic ring toward the 1st and Hip region. We also tested the suitability of structures obtained from NMR data as ‘search fragments’ in the ‘Patterson search approach’ of crystal-structure analysis. It proved possible to resolve the crystal structure of 2 a posteriori with the Patterson search program PATSEE, in this way.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19890720316
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal Structures of Two Modifications of [3,O-didehydro-mebmt1, val2]-cyclosporin and comparison of three different X-ray data sets (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 355-366 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of [3,O-didehydro-MeBmt1, Val2]cyclosporin (PSC-833; 1) was investigated by X-ray analysis. Data were collected from two different crystal modifications. Modification I crystallizes in P3121, a = b = 21.419 (2) Å, c = 32.101 (3) Å with one molecule in the asymmetric unit, modification II in P3221, a = b = 21.313 (2) Å, c = 62.053(3) Å with two molecules per asymmetric unit. This non-immunosuppressive analogue of cyclosporin A adopts a similar backbone conformation to that found in the crystal structure of cyclosporin A and other analogues. Three different data sets of modification I were collected using an Enraf-Nonius-CAD4 diffractometer with CuKα radiation at 20°, a Stoe-Siemens four-circle diffractometer with MoKα radiation at - 120°, and an EMBL image-plate scanner with synchrotron radiation at 12°. The quality of the data sets was evaluated by internal consistency, independent structure solution, and refinement. The structural parameters reported here for modification I are based on the synchrotron data.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780208
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  • 4
    Electronic Resource
    Electronic Resource
    Crystal Structure and Packing of Isocyclosporin A (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 1635-1642 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of isocyclosporin A (1), a rearrangement product of the immunosuppressant drug cyclosporin A, has been determined at 193 (2) K. Crystals are orthorhombic with cell dimensions a = 26.684 (7), b = 26.936 (3) Å, c = 28.549 (7) Å, space group C2221. The structure was solved by direct methods and refined by full-matrix least-squares methods to a conventional R value of 0.110. In contrast to the structure of cyclosprin A in solution and in the crystal, isocyclosporin A (1) has no regular secondary structural elements. The backbone adopts an open, irregular conformation with cis amide bonds between residue 2 and 3, and 3 and 4, respectively. All the other amide bonds and the ester linkage are trans. Contrary to crystal structures of cyclosporin derivatives, this crystal structure is stabilized by two transannular and four intermolecular H-bonds.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790614
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Die Struktur des γ-Naphthocyclinons (1983)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1983 (1983), S. 503-509 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The structure of the γ-NaphthocyclinoneThe crystal structure of γ-naphthocyclinone (1) confirms the chemical and spectroscopic results and shows the configuration of the central bicyclo[3.2.1]octadienone ring to be 6′R, 8′S. The overall shape of 1 resembles a roof with a fold angle of 110° between the two halves of the molecule. The 6′-acetoxy group is situated above the chromophore next to the methylene bridge
    Notes: Die Kristallstruktur des γ-Naphthocyclinons (1) bestätigt die chemischen und spektroskopischen Befunde und weist die Konfiguration im zentralen Bicyclo[3.2.1]octadienon-System als 6′R, 8′S aus. 1 hat eine dachförmige Gestalt; der Winkel zwischen den Molekülhälften beträgt 110°. Die 6′-Acetoxygruppe steht über dem Chromophor in Nachbarschaft zur Methylenbrücke.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198319830314
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of the α-methyl ketoside of 5-amino neuraminic acid methyl ester and its corresponding 5-myristoyl and 5-cyclopropanoyl derivative (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 1111-1114 
    Details
    ISSN: 0170-2041
    Keywords: Sialic acid, 5-azido- ; Neuraminic acid, N-acyl derivatives ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This communication describes the first synthesis of the α-methyl ketoside of an N-unprotected neuraminic acid in the form of its methyl ester (Neu5NH21Me-α-2Me) (5a). This compound is a valuable intermediate for the synthesis of unnatural N-substituted sialic acids. Syntheses of Neusmyristoyl1me-α-2Me (5b) and Neuscyclopropanoyl1me-α-2Me (5c) are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1990199001201
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  • 8
    Electronic Resource
    Electronic Resource
    Preparation and Some Reactions of 1H-1,4-Benzothiazine Ylides (= 1H-1,4-Benzothioniaazin-4-ide) (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 2216-2225 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of fifteen 1H-1,4-benzothiazine ylides were obtained by alkylation of the corresponding 4H-1,4-benzothiazines 1. Ylides of type 2g-r showed slight [1,2] rearrangements upon thermolysis besides main dealkylation to 1 and olefin production. The ylides of this type underwent redox reactions when treated with hydrazine hydrate alone, giving 3,4-dihydro-2H-1,4-benzothiazines mainly, while ylides of type 2a-f failed to react.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680816
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  • 9
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of a new withanolideThe name withanolide has been given to this type of steroidal lactone characterized by a 9-C atom side chain with a 6-membered ring lactone.. Isomeric with withaferin a isolated from withania obtusifolia dun (1986)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 328 (1986), S. 291-294 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19863280220
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  • 10
    Electronic Resource
    Electronic Resource
    Crystal and Molecular Structure of Ambrosin and Damsin, sesquiterpene lactone isolates of Ambrosia maritima L (1988)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 330 (1988), S. 182-190 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ambrosia maritima L. growing wild in central Sudan contained substantial amounts of two principal sesquiterpene lactones, ambrosin and damsin. 1H, 13C-n.m.r.'s and X ray crystal analyses of these are discussed.Much interest and published results on the sesquiterpene plant isolates [1 - 9], the pseudoguiano-lides, ensued from their pharmacological (eg. mollusicidal) activity of the compositae family and in particular the Ambrosinae. From the genus Ambrosia (Compositae, Heliantheae, subtribe Ambro-sinae) several pseudoguianolides (eg. ambrosonolides) were isolated [7 - 12]. Recently, two pseudo-guianolides, damsin and ambrosin were isolated from A. Maritima L. sp. and other six more of these lactones were reported to occur in this species [4].The structures of these compounds were exclusively established through 1H- and 13C-n.m.r. studies which in certain cases were by no means conclusive [4].
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19883300204
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