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  • 1
    Electronic Resource
    Electronic Resource
    Improved electrospray ionization of synthetic oligodeoxynucleotides (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 359-363 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A method is described for rapid purification of synthetic oligodeoxynucleotides to remove sodium counter ions prior to electrospray ionization mass spectrometry. The oligomers, following purification by gel electrophoresis, are precipitated from ammonium acetate to replace sodium ions by ammonium ions, and dissolved in water. Negative-ion electrospray spectra are presented for oligomers with up to 48 residues in which the most intense peaks correspond to the [M—nH]n- ion. The spectrum of 77-mer (Mr24039) shows the predominant peak as due to retention of only a single sodium ion. Changes in the spectra are reported for different instrument orifice voltages and different solution pH. The method should permit rapid, accurate analysis of most typical, synthetic oligodeoxynucleotides.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290050806
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  • 2
    Electronic Resource
    Electronic Resource
    N-Acetyl-D and L-esters of 5′-AMP hydrolyze at different rates (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 150-153 
    Details
    ISSN: 0899-0042
    Keywords: aminoacyl adenylate esters ; hydrolytic stabilization by intramolecular interaction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies of the properties of aminoacyl derivatives of 5′-AMP are aimed at understanding the origin of the process of protein synthesis. Aminoacyl (2′,3′) esters of 5′-AMP can serve as models of the 3′-terminus of aminoacyl tRNA. We report here on the relative rates of hydrolysis of AC-D- and L-Phe AMP esters as a function of pH. At all pHs above 3, the rate constant of hydrolysis of the AC-L-Phe ester is 1.7 to 2.1 times that of AC-D-Phe ester. The D-isomer seems partially protected from hydrolysis by a stronger association with the adenine ring of the 5′-AMP. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050308
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  • 3
    Electronic Resource
    Electronic Resource
    Disposition kinetics of ML-1035 sulfoxide enantiomers and the prochiral sulfide in rats (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 428-435 
    Details
    ISSN: 0899-0042
    Keywords: enantiomeric pharmacokinetics ; benzamides ; gastroprokinetic agents ; prochirality ; chiral sulfoxidation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ML-1035, 4-amino-5-chloro-2-[2-(methylsulfinyl)ethoxy]-N-[2-(diethylamino)ethyl]benzamide, is a sulfoxide compound and a racemic gastroprokinetic agent with a chiral center at the sulfur atom. We have investigated the disposition kinetics of (R)-ML-1035 sulfoxide (R) and (S)-ML-1035 sulfoxide (S) after the single enantiomers and the racemic mixture were administered to rats in separate experiments. There was no noticeable chiral inversion after either enantiomer dose. Both enantiomers were rapidly absorbed. After dosing with enantiomers or with the racemate, the resulting plasma concentration-time curve of R was closely parallel to that of S in both intravenous and oral experiments, suggesting that the two enantiomers have approximately the same disposition kinetics. After intravenous enantiomer doses, only S underwent conversion to sulfide, suggesting that sulfidation in the liver is enantioselective. However, the enantioselective sulfidation after intravenous dosing did not introduce a difference in the global plasma disposition profiles between R and S, since the reduction reaction is a minor metabolic process. Other metabolic reactions such as sulfonation and mono-N-desethylations were not enantioselective. After oral administration, conversion to sulfide was observed for both enantioners, implicating the existence of a nonhepatic pathway in sulfidation. Administration of a prochiral sulfide dose was associated with an enantioselective sulfoxidation, in which the R/S concentration ratios increased as a function of time. In addition, enantiomeric interaction causing changes in pharmacokinetic parameters was observed after the oral racemate dose, while the interaction is negligible after an intravenous racemate dose, indicating a route dependency in enantiomeric interaction. © 1993 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050607
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of Aristotelia-Type Alkaloids. Part XVPart XIV: See [1].. Total synthesis of (+)-hobartinol (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 292-300 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic (+)-makomakine (6) was transformed in six steps into (+)-17R,18R)-17,18-dihydrohobartine-17,18-diol ((+)-5) with an overall yield of 38% (Scheme 2). This compound was shown to be identical with natural hobartinol, a monoterpene indole alkaloid from Aristotelia australasica, originally believed to be the (17S)-epimer 1. At the same time, the synthesis of (+)-5 delineates the hitherto unknown absolute configuration of this metabolite.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19950780204
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  • 5
    Electronic Resource
    Electronic Resource
    Borane Reduction of the Steroid 20-Ketone Group in the Presence of Various Chiral β-Amino Alcohols (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 581-582 
    Details
    ISSN: 0170-2041
    Keywords: 5β-Pregnane, 3α-hydroxy-20-one ; Chiral borane reduction ; Borane reduction ; Steroids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The direction of reduction of 20-carbonyl group of 3α-hydroxy-5β-pregnan-20-one (1) with a complex of borane-methyl sulfide and chiral β-amino alcohols, depends on the chirality of the amino alcohol. Where there is a 2-phenyl or 2-benzyl substituent, then the S enantiomer gives exclusively the steroid 20R alcohol 3. The R enantiomer of 2-amino-2-phenyl-1-ethanol gives the highest steroid 20S (2):20R (3) alcohol ratio.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199319930194
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and oxidation of pregna-3,5-dien-20-ols and -20-one and selective reduction of pregna-3,5-dien-20-one (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 213-215 
    Details
    ISSN: 0170-2041
    Keywords: Steroids ; Pregna-3,5-dien-20-one, oxidation, reduction ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pregna-3,5-dien-20-one (4) and (20S)- and (20R)-pregna-3,5-dien-20-ol (2 and 3) were synthesized from progesterone. Oxidation of a mixture of 2 and 3 with Jones reagent gave 4, while a large excess of Jones reagent afforded besides 4, 6-oxoprogesterone (5), 6β-hydroxyprogesterone (6) and 5α-pregnane-3,6,20-trione (7). With L-selectride as reducing agent, reduction of 4 led to 2 and 3 in a ratio of about 1:1. However, some reducing agents gave a higher ratio of isomer 3.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199019900139
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  • 7
    Electronic Resource
    Electronic Resource
    The mass spectra of diethylstilbestrol and related compoundsThis is Publication No. 1553 of the Cancer Commission of Harvard University. Supported by Grants CHD08457 from The National Institute of Child Health and Human Development and CA013193 from The National Cancer Institute. High resolution mass spectra were obtained at the Masschusetts Institute of Technology Mass Spectrometry Facility which is operated under grant RR 00317 from the Biotechnology Resources Branch, Division of Research Resources, National Institutes of Health.Abbreviations: Diethylstilbestrol (DES) = E3,4-bis (p-hydroxyphenyl)-hex-3-ene; dimethylstilbestrol (DMs) = E, 2,2-bis-(p-hydroxylphenyl)-but-2-ene; dienestrol = E, 2,2-bis-(p-hydroxyphenyl)-but-2-ene; dienestrol = E, E-3,4-bis-(p-hydroxyphenyl)-hexa-2,4-dien and hexestrol for 2,4-bis-(p-hydroxyphenyl) - hexane. (1978)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1978), S. 582-586 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The low resolution mass spectra of E-3,4-bis-(p-hydroxyphenyl)-hex-3-ene (diethylstilbestrol), E-[1,1,1-3H3]3,4-bis-(p-hydroxyphenyl)-hex-3-ene, E-2,3-bis-(p-hydroxyphenyl)-but-2-ene (dimethylstilbestrol), E,E-3,4-bis-(p-hydroxyphenyl)hexa-2,4-diene (dienestrol) and 3,4-bis-(p-hydroxyphenyl)-hexane (hexestrol) were examined as the parent compounds, their diacetates, dimethyl ethers, and bis-trimethylsilyl ethers. In addition, the mass spectra of the diethyl ether and the hexadeuteriodimethyl ether of E-3,4-bis-(p-hydroxyphenyl)-hex-3-ene were studied. Each compound gives rise to several sets of characteristic fragment ions associated with loss of alkyl groups, loss of aryl groups and rearrangements. An ion of m/e 16 (C13H9) was found in the spectra of all the compounds studied. With the aid of high resolution mass spectrometry empirical formulae were assigned to major ions of the free diphenols.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200051007
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  • 8
    Electronic Resource
    Electronic Resource
    Low-temperature isospecific polymerization of propylene catalyzed by alkylzirconocene-type ‘cations’ (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 7 (1993), S. 71-74 
    Details
    ISSN: 0268-2605
    Keywords: Polypropylene ; polymerization ; isospecificity ; alkylzirconocene-type cations ; stereoselectivity ; MAO ; cationic catalysts ; trityl tetrakis(pentafluorophenyl)borate ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rac-ethylenebis(indenyl)methylzirconium ‘cation’ (1), generated from rac-Et(Ind)2ZrMe2 and Ph3CB(C6F5)4, has recently been shown to be exceedingly active and stereoselective in propylene polymerization. The ethyl analog (2) can be produced by an alternate, efficient route involving a reaction between rac-Et(Ind)2ZrCl2 and AlEt3 (TEA), followed by addition of Ph3CB(C6F5)4. The use of excess AlEt3 serves both to alkylate the zirconium complex as well as to scavenge the system. The propylene polymerization activity of the ‘cation’ 2 is about 7000 times greater than the activity of rac-Et(Ind)2ZrCl2/methylaluminoxane (MAO) at Tp=-20°C. The related catalyst system rac-Me2Si(Ind)2ZrCl2/TEA/Ph3CB(C6F5)4 (3) was found to produce 98.3% i-PP with Tm 156.3°C and an activity of 1.8 × 109 g PP {(mol Zr) [C3H6]h}-1.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590070109
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  • 9
    Electronic Resource
    Electronic Resource
    (η5-Pentamethylcyclopentadienyl)trimethyltitanium as a precursor for the syndiospecific polymerization of styrene (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 8 (1994), S. 393-396 
    Details
    ISSN: 0268-2605
    Keywords: Polystyrene ; syndiotactic ; syndioselective ; MAO ; cationic catalysts ; trityl tetrakis(pentafluorophenyl)borate ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An equimolar mixture of Cp*Ti(CH3)3 (2) and Ph3C+[B(C6F5)4]- (1) forms a highly active and syndioselective catalyst for the polymerization of styrene, producing 96% syndiotactic polystyrene (PS) at an activity of 0.91 × 107 g PS (mol Ti)-1 (mol styrene)-1 h-1. Both activity and syndioselectivity can be increased using tri-isobutylaluminum (TIBA) to scavenge the system. ESR measurements indicate that the polymerization proceeds via titanium(IV) intermediates. Catalysts derived from 2/methylaluminoxane (MAO) as well as Cp*TiCl3/MAO also function as syndioselective styrene polymerization catalysts, but are less active than the ‘cationic’; system derived from 1 and 2.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590080413
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  • 10
    Electronic Resource
    Electronic Resource
    Substituent effects on titanocenium catalysts (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 8 (1994), S. 437-443 
    Details
    ISSN: 0268-2605
    Keywords: Titanocenium ; olefin polymerizations ; Ziegler-Natta catalysis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Titanocene dichloride (1) and its bis(trifluoromethyl) (2) and bis(N,N-dimethylamino) (3) derivatives have been compared as catalysts for ethylene and propylene polymerizations using both methylaluminoxane (MAO) and triphenylcarbenium tetrakis(pentafluorophenyl)borate (4)/triisobutylaluminum (TIBA) as cocatalysts. The differences between the activities of the three ‘free’ titanocenium ions and the Mw of the polyolefins produced by them may be attributable to the relative stabilities of the intermediate olefin-titanocenium π-complexes. Interaction of either the neutral MAO or its anion with the titanocenium species may be responsible for the significantly lower catalytic efficiencies when the precursors were activated by MAO than by the 4/TIBA system.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590080503
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