TY - JOUR
T1 - The remote-oxyfunctionalization of unactivated carbons in (5β)-3-oxobile acids by 2,6-dichloropyridine N-oxide catalyzed by ruthenium-porphyrin and HBr
T2 - A direct lactonization at C-20
AU - Ogawa, Shoujiro
AU - Iida, Takashi
AU - Goto, Takaaki
AU - Mano, Nariyasu
AU - Goto, Junichi
AU - Nambara, Toshio
PY - 2004/4/7
Y1 - 2004/4/7
N2 - 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.
AB - 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.
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U2 - 10.1039/b314965j
DO - 10.1039/b314965j
M3 - Article
C2 - 15034624
AN - SCOPUS:2342582711
SN - 1477-0520
VL - 2
SP - 1013
EP - 1018
JO - Organic and Biomolecular Chemistry
JF - Organic and Biomolecular Chemistry
IS - 7
ER -