共查询到20条相似文献,搜索用时 15 毫秒
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Adamus G Montaudo MS Montaudo G Kowalczuk M 《Rapid communications in mass spectrometry : RCM》2004,18(13):1436-1446
A series of aliphatic copolyesters was obtained from (R,S)-beta-butyrolactone and two isomeric hydroxy acids, 6-hydroxyhexanoic and (R,S)-2-hydroxyhexanoic acids. The reactions were conducted in bulk without catalyst. Electrospray ionization tandem mass spectrometry (ESI-MSn) was used for molecular characterization of these copolyester oligomers. The mass spectra of the copolyesters studied have enabled identification of their molecular structures including chemical nature of the end groups (hydroxyl and carboxylate). The compositions of the oligocopolyesters and their sequence distributions were determined based on measurement of the relative intensities of the individual oligocopolyester peaks in the ESI mass spectra. The mass spectra (MS1) provided information on composition and sequence distribution, and small deviations from Bernoulli statistics were detected. The arrangement of co-monomer structural units along the oligopolyester chains was verified by MS/MS experiments and investigation of the fragmentation pathways. 相似文献
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Michał Kawalec Grażyna Adamus Piotr Kurcok Marek Kowalczuk 《Macromolecular Symposia》2007,253(1):59-64
Summary: New synthetic pathway of a-PHB/PEG/a-PHB triblock amphiphilic copolymers is presented. The copolymers are obtained via racemic BL polymerization initiated with respective PEG macroinitiators. The structure of resulting block copolymers has been proved by SEC and NMR spectroscopy. 相似文献
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[reaction: see text] The asymmetric synthesis of pentacyclic derivatives was achieved in a single step starting from enantiopure [(S)R]-[(p-tolylsulfinyl)methyl]-p-quinols or the nitrogen analogue, through a domino sequence involving four conjugate additions in excellent yields. Eight new stereogenic centers were created in one step and in a highly diastereoselective manner. 相似文献
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I. V. Bakhanova V. N. Nesterov S. K. Moiseev H. Schmidhammer V. N. Kalinin 《Russian Chemical Bulletin》1998,47(11):2177-2181
The crystal structures and absolute configurations of (6R,7R,14S)-6,14-etheno-7-[(1R)-1-hydroxyethyl]-6,7,8,14-tetrahydro-17-nor-17-phenylthebaine and (6R,7R,14S)-6,14-etheno-7-[(1S)-1-hydroxyethyl]-6,7,8,14-tetrahydro-17-nor-17-phenylthebaine were established by X-ray diffraction analysis.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2245–2250, November, 1998. 相似文献
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Harding WW Hodge M Wang Z Woolverton WL Parrish D Deschamps JR Prisinzano TE 《Tetrahedron: Asymmetry》2005,16(13):2249-2256
The enantioselective synthesis of the (R,R)- and (S,S)-enantiomers of 1 from commercially available 3-chlorocinnamic acid is reported. The Sharpless asymmetric epoxidation was used to establish the stereocenters in the synthesis of both enantiomers of 1. 相似文献
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Gimalova F. A. Sadretdinov I. F. Spirikhin L. V. Miftakhov M. S. 《Russian Journal of Organic Chemistry》2003,39(9):1234-1239
Deprotonation of 1-[(1S,3R)-2,2-dimethyl-3-(2-methoxymethyloxyethyl)cyclopropyl]-2-propanone with lithium diisopropylamide in THF at -78°C and subsequent treatment of the resulting enolate with Me3SiCl yielded mainly the corresponding terminal silyl enol ether. The condensation of intermediate enolate with benzaldehyde regioselectively afforded a mixture of the corresponding aldol and its dehydration product. The reactions of the title ketone with NBS, as well as of the silyl enol ethers derived therefrom with I2, led to formation of mixtures of products via opening of the cyclopropane ring. 相似文献
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N-Methyl-N-[(1S)-1-[(3R)-pyrrolidin-3-yl]ethyl]amine (1)(1) is a key intermediate in the preparation of premafloxacin (2), which was under development as an antibiotic for use against pathogens of veterinary importance. This paper describes the development of a practical, efficient, and stereoselective process for the preparation of 1 from isobutyl (3S)-3-[methyl[(1S)-1-phenylethyl]amino]butanoate (5c). The key steps in the synthetic sequence are an asymmetric Michael addition, which yields 5c, and a stereoselective alkylation, which yields (3S,4S)-3-allyl-1,4-dimethylazetidin-2-one (17). 相似文献
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