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Stereoselective Synthesis and NMR Characterization of C-24 Epimeric Pairs of 24-Alkyl Oxysterols.
MedLine Citation:
PMID:  23197084     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Two pairs of C-24 epimeric (24R)-/(24S)-24-hydroxy-24-methyl-5α-cholestan-3β-yl acetates and (24R)-/(24S)-25-hydroxy-24-methyl-5α-cholestan-3β-yl acetates as well as some related 24-ethyl oxysterol analogs were stereoselectively synthesized directly from the respective parent 24-alkyl sterols by a remote O-insertion reaction with 2,6-dichloropyridine N-oxide (DCP) in the presence of a catalytic amount of (5,10,15,20-tetramesitylporphrinate) ruthenium(II) carbonyl complex [Ru(TMP)CO] and HBr. (1)H- and (13)C-NMR signals serving to differentiate each of the two epimeric pairs were interpreted. The C-24 alkyl oxysterols epimeric at C-24 were found to be effectively characterized by the aromatic solvent-induced shift (ASIS) by C(5)D(5)N, particularly for the difference in the (13)C resonances in the substituted cholestane side chain. A method for differentiating the (1)H and (13)C signal assignment of the terminal 26-/27-CH(3) in the iso-octane side chain was also discussed on the basis of a combined use of the preferred conformational analysis and HMQC and HMBC techniques. The present method may be useful for determining the stereochemical configuration at C-24 of this type of 24-alkyl oxysterols.
Authors:
Shoujiro Ogawa; Hiroaki Kawamoto; Takashi Mitsuma; Hiroki Fujimori; Tatsuya Higashi; Takashi Iida
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-30
Journal Detail:
Title:  Lipids     Volume:  -     ISSN:  1558-9307     ISO Abbreviation:  Lipids     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-30     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0060450     Medline TA:  Lipids     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Faculty of Pharmaceutical Sciences, Tokyo University of Science, Noda, Chiba, 278-8510, Japan.
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