The remote-oxyfunctionalization of unactivated carbons in (5β)-3-oxobile acids by 2,6-dichloropyridine N-oxide catalyzed by ruthenium-porphyrin and HBr: A direct lactonization at C-20

Shoujiro Ogawa, Takashi Iida, Takaaki Goto, Nariyasu Mano, Junichi Goto, Toshio Nambara

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17 Citations (Scopus)

Abstract

Remote-oxyfunctionalization induced by 2,6-dichloropyridine N-oxide (DCP N-oxide) as an oxygen donor and a (5,10,15,20-tetramesitylporphyrinate) ruthenium(n) carbonyl complex (Ru-porphyrin) and HBr as catalysts was examined for a series of methyl ester-peracetylated derivatives of (5β)-3-oxobile acids. Using the DCP-N-oxide/Ru-porphyrin/HBr system, 5β-hydroxylation predominated for the substrates having a 12-acetoxyl substituent due to steric hindrance, but the presence of a 7-acetoxyl substituent decreased the reactivity of the 5β-position allowing for the competitive (20S)-20- oxyfunctionalization, subject to electronic constraints. A variety of novel 5β-hydroxylation and (20S)-24,20-γ-lactonization products, as well as their double-oxyfunctionalization and dehydration products, were obtained in one-step. The alkaline hydrolysis of the γ-lactones gave the corresponding stereoselective (20S)-20-hydroxy-carboxylic acids.

Original languageEnglish
Pages (from-to)1013-1018
Number of pages6
JournalOrganic and Biomolecular Chemistry
Volume2
Issue number7
DOIs
Publication statusPublished - 2004 Apr 7

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry

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