- CaF2 catalyzed SN2 type chlorodehydroxylation of chiral secondary alcohols with thionyl chloride: A practical and convenient approach for the preparation of optically active chloroalkanes
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A CaF2 catalyzed chlorodehydroxylation of chiral secondary alcohols with thionyl chloride has been developed. The chlorination reaction is effective for a wide range of alcohols, generating the corresponding chloroalkanes in good yield with high optical purity with inversion of the original configuration of the alcohol.
- Zhang, Junjie,Wang, Huanxia,Ma, Yun,Wang, Youming,Zhou, Zhenghong,Tang, Chuchi
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p. 2261 - 2263
(2013/05/09)
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- Enantioselectivity of haloalkane dehalogenases and its modulation by surface loop engineering
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In the loop: Engineering of the surface loop in haloalkane dehalogenases affects their enantiodiscrimination behavior. The temperature dependence of the enantioselectivity (lnE versus 1/T) of β-bromoalkanes by haloalkane dehalogenases is reversed (red data points) by deletion of the surface loop; the selectivity switches back when an additional single-point mutation is made. This behavior is not observed for -bromoesters.
- Prokop, Zbynek,Sato, Yukari,Brezovsky, Jan,Mozga, Tomas,Chaloupkova, Radka,Koudelakova, Tana,Jerabek, Petr,Stepankova, Veronika,Natsume, Ryo,Van Leeuwen, Jan G. E.,Janssen, Dick B.,Florian, Jan,Nagata, Yuji,Senda, Toshiya,Damborsky, Jiri
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supporting information; experimental part
p. 6111 - 6115
(2010/11/05)
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- N-Thiolated β-lactam antibacterials: Effects of the N-organothio substituent on anti-MRSA activity
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A study on the structure-activity profiles of N-thiolated β-lactams 1 is reported which demonstrates the importance of the N-organothio moiety on antibacterial activity. Our results indicate that elongation of the N-alkylthio residue beyond two carbons, or extensive branching within the organothio substituent, diminishes antibacterial effects. Of the derivatives we examined, the N-sec-butylthio β-lactam derivative 5g possesses the strongest growth inhibitory activity against methicillin-resistant Staphylococcus aureus strains. Sulfur oxidation state is important, as the N-sulfenyl and N-sulfinyl groups provide for the best antibacterial activity, while lactams bearing the N-sulfonyl or N-sulfonic acid functionalities have much weaker or no anti-MRSA properties. Stereochemistry within the organothio chain does not seem to be a significant factor, although for N-sec-butylthio β-lactams 15a-d, the 3R,4S-lactams 15c, d are more active than the 3S,4R-stereoisomers 15a, b in agar diffusion experiments. The N-methylthio lactams are the most sensitive to the presence of glutathione, followed by N-ethylthio and N-sec-butylthio lactams, which indicates that bioactivity and perhaps bacterial selectivity of the lactams may be related to the amount of organothiols in the bacterial cell. These results support the empirical model for the mechanism of action of the compounds in which the lactam transverses the bacterial membrane to deliver the organothio moiety to its cellular target.
- Heldreth, Bart,Long, Timothy E.,Jang, Seyoung,Reddy, G. Suresh Kumar,Turos, Edward,Dickey, Sonja,Lim, Daniel V.
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p. 3775 - 3784
(2007/10/03)
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- Stereochemical dissection of a carbene fragmentation reaction
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The fragmentation of (S)-3-(2-butoxy)-3-chlorodiazirine (9) in acetonitrile proceeds via N2 loss to (5)-2-butoxy-chlorocarbene (10) and thence via CO scission to a 2-butyl cation/chloride anion pair (11) that collapses to (5)-2-chlorobutane (12) with ~56% net retention. In 1-butanol, ion pair 11 affords 55% chloride 12 by ion pair return with 82% net retention and 45% of (R)-2-butyl 1-butyl ether (13) by ion pair solvolysis with ~71% net inversion.
- Moss, Robert A.,Balcerzak, Pawel
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p. 9386 - 9390
(2007/10/02)
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