51646-05-0Relevant articles and documents
A study of the epoxidation of cycloolefins by the t-buoh copper-permanganate system
Baqi, Younis,Giroux, Simon,Corey
, p. 959 - 961 (2009)
Evidence is presented that Cu(MnO4)2 effectively epoxidizes trisubstituted steroid olefins by a nonconcerted pathway.
Biosynthesis of 20-hydroxyecdysone in plants: 3β-Hydroxy-5β-cholestan-6-one as an intermediate immediately after cholesterol in Ajuga hairy roots
Fujimoto, Yoshinori,Maeda, Izumi,Ohyama, Kiyoshi,Hikiba, Juri,Kataoka, Hiroshi
, p. 59 - 64 (2015/02/19)
3β-Hydroxy-5β-cholestan-6-one was identified in the EtOAc extract of Ajuga hairy roots by micro-analysis using LC-MS/MS in the multiple reaction mode (MRM). Furthermore, administration of (2,2,4,4,7,7-2H6)- and (2,2,4,4,6,7,7-2H7)-cholesterols to the hairy roots followed by LC-MS/MS analysis of the EtOAc extract of the hairy roots indicated that cholesterol was converted to the 5β-ketone with hydrogen migration from the C-6 to the C-5 position. These findings, in conjunction with the previous observation that the ketone was efficiently converted to 20-hydroxyecdysone, strongly suggest that the 5β-ketone is an intermediate immediately formed after cholesterol during 20-hydroxyecdysone biosynthesis in Ajuga sp. In addition, the mechanism of the 5β-ketone formation from cholesterol is discussed.
Surface functionalization of supported Mn clusters to produce robust Mn catalysts for selective epoxidation
Muratsugu, Satoshi,Weng, Zhihuan,Tada, Mizuki
, p. 2020 - 2030 (2013/09/24)
A robust heterogeneous Mn catalyst for selective epoxidation was prepared by the attachment of a Mn4 oxonuclear complex [Mn4O 2(CH3COO)7(bipy)2](ClO 4)·3H2O (1) on SiO2 and the successive stacking of SiO2-matrix overlayers around a supported Mn cluster. The structures of supported Mn catalysts were characterized by means of FT-IR spectroscopy, diffuse-reflectance UV/vis spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and Mn K-edge X-ray absorption fine structure. A ligand exchange reaction between the CH3COO ligand of 1 and surface silanol group produced a SiO2-supported Mn cluster (2), whose coordination structure was similar to 1. Subsequent heating of 2 under vacuum yielded supported Mn clusters (3, 4) through the partial elimination of CH 3COO ligands. The surface-attached Mn clusters of 2, 3, and 4 were easily released to a reaction solution under epoxidation conditions (Mn leaching: approximately 50%), although they were active for epoxidation of trans-stilbene (the conversion of trans-stilbene, 99%, and the selectivity of trans-stilbene epoxid, 96%, for 6 h on 3). We found that the functionalization of the supported Mn cluster on 2 with surface SiO2-matrix overlayers altered the reactivity of the supported Mn cluster. Dimeric Mn species (5c) with reduced Mn oxidation state and coordination numbers was formed together with a reaction nanospace surrounded by the SiO2-matrix overlayers. By optimizing the stacking manner of the SiO2-matrix overlayers, the durability of the Mn catalyst was remarkably improved from leaching (the Mn leaching reached the minimum value of 0.01%), and active and stable epoxidation performances were successfully achieved in the heterogeneous phase (the conversion of trans-stilbene, 97%, and the selectivity of trans-stilbene epoxide, 91%, for 31 h on 5c).
