A two-step mechanism has been proposed that indicates that the catalytic process proceeds via trans-diaxial elimination of the 1α,2β hydrogen atoms from a 3-ketosteroid substrate [30]. Interaction of the C3 carbonyl group of a steroidal substrate with an electrophile promotes labilization of ...
(75%:25%; ΔG° = 0.42 kcal mol−1) with a preference for the diaxial conformer was found, due to the anomeric effect which also dominates the conformational equilibrium of 3-methoxy-1,2,4,5-tetroxane; the axial conformer was found, in agreement with the X-ray structure <1998AHC(...
Here, aromatization alters the pseudodiaxial conformation, elongating the C3-O distance, pla- cing strain on the IGA substrate to break the C-O bond, and steering the separation of the products through a pericyclic mechanism (Fig. 3c, d)30. To investigate the energetics for the proposed ...
The copper(II) compound has both the C2 and C9 substituents equatorially oriented and with 1,3-diaxial methyl substitution of one of the six-membered chelate rings. Disorder prevented unambiguous assignment of configuration for trans-[Ni(mr-L-III))(NCS)2], originally reported as trans-[Ni(...
They allow 1,2-diaxial eliminations of HBr leading to PBCDens 5b and 3a, when starting with (+)β- and (−)β-HBCD (A,B). PBCDen 8b is the expected product for both ε-HBCD-enzyme complexes (C,D). 4. Conclusions The large-scale application of HCHs as insecticides, until the ...
positions and orientations relative to the substrate suggest that the enzyme likely imposes an unfavorable constraint on the native substrate IGA. Here, aromatization alters the pseudodiaxial conformation, elongating the C3-O distance, placing strain on the IGA substrate to break the C-O bond, and...