57-91-0Relevant articles and documents
One-Step Chemo-, Regio- and Stereoselective Reduction of Ketosteroids to Hydroxysteroids over Zr-Containing MOF-808 Metal-Organic Frameworks
Llabrés i Xamena, F. X.,Mautschke, H.-H.
, p. 10766 - 10775 (2021/06/15)
Zr-containing MOF-808 is a very promising heterogeneous catalyst for the selective reduction of ketosteroids to the corresponding hydroxysteroids through a Meerwein-Ponndorf-Verley (MPV) reaction. Interestingly, the process leads to the diastereoselective synthesis of elusive 17α-hydroxy derivatives in one step, whereas most chemical and biological transformations produce the 17β-OH compounds, or they require several additional steps to convert 17β-OH into 17α-OH by inverting the configuration of the 17 center. Moreover, MOF-808 is found to be stable and reusable; it is also chemoselective (only keto groups are reduced, even in the presence of other reducible groups such as C=C bonds) and regioselective (in 3,17-diketosteroids only the keto group in position 17 is reduced, while the 3-keto group remains almost intact). The kinetic rate constant and thermodynamic parameters of estrone reduction to estradiol have been obtained by a detailed temperature-dependent kinetic analysis. The results evidence a major contribution of the entropic term, thus suggesting that the diastereoselectivity of the process is controlled by the confinement of the reaction inside the MOF cavities, where the Zr4+ active sites are located.
Catalytic properties of pristine and defect-engineered Zr-MOF-808 metal organic frameworks
Mautschke,Drache,Senkovska,Kaskel,Llabrés Xamena
, p. 3610 - 3616 (2018/07/29)
Various defect-engineered Zr-trimesate MOF-808 compounds (DE-MOF-808) have been prepared by mixing the tricarboxylate ligands with dicarboxylate ligands; viz. isophthalate, pyridine-3,5-dicarboxylate, 5-hydroxy-isophthalate, or 5-amino-isophthalate. The resulting mixed-ligand compounds, MOF-808-X (X = IP, Pydc, OH or NH2) were all found to be highly crystalline and isostructural to the unmodified MOF-808. Pristine MOF-808 showed better catalytic performance than a UiO-66 reference compound for the Meerwein-Ponndorf-Verley (MPV) reduction of carbonyl compounds. This was attributed to a higher availability of coordinatively unsaturated Zr4+ sites (cus) in MOF-808 upon removal of formate ions. Meanwhile, cus in UiO-66 are only located at defect sites and are thus much less abundant. Further improvement of the catalytic activity of defect-engineered MOF-808-IP and MOF-808-Pydc was observed, which may be related with the occurrence of less crowded Zr4+ sites in DE-MOF-808. The wider pore structure of MOF-808 with respect to UiO-66 compounds translates into a sharp improvement of the activity for the MPV reduction of bulky substrates, as shown for estrone reduction to estradiol. Interestingly, MOF-808 produces a notable diastereoselectivity towards the elusive 17-α-hydroxy estradiol.
Application of in Situ FTIR for the Preparation of 17-α-Estradiol via Mitsunobu Reaction
Cardoso, Flávio S. P.,Mickle, Gregory E.,Da Silva, Marco A.,Baraldi, Patricia T.,Ferreira, Fabio B.
, p. 306 - 311 (2016/03/04)
An efficient synthesis of 17-α-estradiol 1 is described. Utilization of in situ IR allowed for an online monitoring of the key Mitsunobu reaction and development of a safe and reliable synthesis of 17-α-estradiol 1 in 78% overall yield over three steps. Benzoylation of 17-β-estradiol 2 is conducted at high regioselectivity under phase-transfer catalysis (PTC) conditions, followed by a Mitsunobu reaction to invert the chiral center at C-17 and provide intermediate 5, containing the core structure of 17-α-estradiol 1. Finally, the desired active pharmaceutical ingredient (API) is prepared by saponification of the remaining esters.