- VIBRATIONAL SPECTRA AND CONFORMATIONAL ANALYSIS OF CHLOROMETHYCHLOROFORMATE
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Infrared spectra of vapour and low temperature amorphous solid phases and Raman spectra of vapour, liquid and low temperature amorphous solid phases of ClCOOCH2Cl, ClCOOCD2Cl and ClCOOCDHCl are reported.The spectra indicate the presence of the same single conformer in each of these phases.Asymmetric top contour simulation of some vapour phase IR bands shows the conformer has s-cis orientation of the ester function and gauche orientation of the chloromethyl grouping.This conclusion is substantiated by the study of C-H and C-D stretches in mid-IR and near-IR spectra of ClCOOCHDCl in different phases.The assignments are augmented by a normal coordinate analysis using a transferable simplified valence force field.The latter is used to assign the splittings observed in the d1-derivative.
- Daeyaert, F.,Veken, B. J. van der
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- Water-mediated proton transfer: A mechanistic investigation on the example of the hydration of sulfur oxides
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We outline general mechanistic features of "water-mediated proton transfer" in the example of the isomerization reaction in hydrogen-bonded sulfur oxide-water supermolecules containing up to three water molecules. The nucleophilic attack of a water oxygen on the sulfur atom occurs concertedly with the (multiple) protontransfer event(s). The protons are transferred according to the well-known hydrogen-bond compression mechanism. However, contrary to "pure" multiple proton-transfer reactions, the protons are transferred asynchronously. These mechanistic features force the reaction to be classical rather than quantum-tunneling-dominated down to rather low temperatures. In the quantum-dominated temperature region, tunneling takes place only if all protons tunnel through the barrier. Straight line corner cutting (large curvature tunneling) does not dominate at any temperature, as the reduced mass corresponding to reaction coordinate motion does not drop to values low enough in the reaction barrier region. The asymmetric nature of the potential energy surface even allows different mechanisms involving transient H3O+ rotation termed "molecular swing" and a H2SO3 isomerization to be favorable compared to water-mediated triple proton transfer in the case of three participating water molecules.
- Loerting, Thomas,Liedl, Klaus R.
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- Some new acyclic nucleotide analogues as antiviral prodrugs: Synthesis and bioactivities in vitro
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A series of ester analogues of acyclic nucleotide PMPA and PMEA were synthesized as potent antiviral agents. The antiviral evaluation results indicated that bis benzyl ester prodrug of PMPA 5f and bis allyl ester prodrug of PMEA 5g exhibited potent antiviral activities. The IC50 of 5f for HBV was 2.15 μM, and the IC50 of 5g for HIV-1 was 1.61 μM.
- Tang, Yan-bo,Peng, Zong-gen,Liu, Zong-ying,Li, Yan-ping,Jiang, Jian-dong,Li, Zhuo-rong
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p. 6350 - 6353
(2008/09/17)
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- Method for purifying chloromethyl chloroformate
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Describes a method for obtaining substantially pure chloromethyl chloroformate from a chloroformate mixture comprising chloromethyl chloroformate and methyl chloroformate by heating the chloroformate mixture in a reaction zone at temperatures ranging from at least 50° C. to the reflux temperature of the chloroformate mixture in the reaction zone while simultaneously removing volatile gaseous decomposition products from the reaction zone. Dichloromethyl chloroformate may also be present in the chloroformate mixture.
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- Acyloxymethyl carbonochloridates. New intermediates in prodrug synthesis
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The synthesis of a number of stable acyloxymethyl carbonochloridates 7 has been accomplished in four steps from chloromethyl carbonochloridate 3. Each step has been optimized with propanoyl-oxymethyl carbonochloridate 7c as a model compound (64% overall yield). Diethyl ether-boron trifluoride catalyzes the conversion of carbonothioate 6cc to the carbonochloridate 7c by chlorination with sulfuryl chloride. Acylation of a few compounds containing hydroxy or amino groups by 7c is described.
- Folkmann,Lund
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p. 1159 - 1166
(2007/10/02)
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- Specificity of esterases and structure of prodrug esters: Reactivity of various acylated acetaminophen compounds and acetylaminobenzoated compounds
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The relative rates of enzymatically catalyzed hydrolysis of various esters of p-acetylaminobenzoic acid (APAB) and variously acylated acetaminophen (APAP) derivatives were measured. Neutral, anionic, and cationic esters were examined. The enzyme sources adopted were rat intestinal homogenate, rat liver homogenate, rat plasma, and a partly purified commercial enzyme. In both APAB and APAP esters, neutral esters were the most sensitive of the enzyme sources examined, and the sensitivity was due to the carbon chain length. The APAP esters were enzymatically more stable than the APAP esters. The relative rates of hydrolysis of these esters varied depending on the enzyme source. The ability of structure recognition was good in rat intestinal homogenate, but weak in rat plasma. These results suggest that ester prodrugs can be designed to cleave preferentially at selected sites along the pathway between absorption and disposition in the body.
- Seki,Kawaguchi,Higuchi
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p. 855 - 860
(2007/10/02)
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- Total Synthesis of 3-(5-Tetrazolyl)carbapenems
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The synthesis of the title compounds, β-lactam antibiotics, is described.A new tetrazole protecting group, (((p-nitrobenzyl)carbonyl)oxy)methyl, was succesfully applied.Substitution of carboxyl by tetrazole on the carbapenem nucleus results in stability to a degradative renal enzyme.
- Andrus, Alex,Heck, James V.,Christensen, Burton G.,Partridge, Beverly
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p. 1808 - 1811
(2007/10/02)
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- Derivatives of ampicillin and amoxicillin with beta-lactamase inhibitors
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Certain beta-lactamase inhibitors which have a beta-lactam ring as well as a carboxy group have been linked through their carboxy group to either the amino group of ampicillin, the amino group of amoxicillin or the phenolic hydroxy group of amoxicillin. This affords novel antibacterial agents.
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