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Nuclear Overhauser effect spectroscopy coupling constant determination

The relative stereochemistry of hyperaspine 93 was determined by 2-D NMR spectroscopic and mass spectrometry (MS) methods. It has a m-fused bicyclic conformation 93a <2001TL4621>. The trans-fused one is disfavored by an axial pentyl group at C-8 and by a destabilizing dipole-dipole interaction between the N- and O-atoms, which does not exist in the alternative //.(-conformation. The geminal coupling constant of C( 1 )H2 in 93 (11.0 Hz), and that of its 6-hydroxy derivative (11.2 Hz), indicates that they exist preferentially in / //-conformations, whereas their 6-epimers adopt trans-conformations (9.3 and 8.4 Hz, respectively) <2005EJ01378>. Nuclear Overhauser enhancement spectroscopy (NOESY) studies also confirmed the stereochemistry of 93 by the marked nuclear Overhauser effect (NOE) correlation between H-3 and H-4a <20030L5063>. [Pg.94]

See other pages where Nuclear Overhauser effect spectroscopy coupling constant determination is mentioned: [Pg.111]    [Pg.6213]    [Pg.124]    [Pg.203]    [Pg.6212]    [Pg.2]    [Pg.336]    [Pg.8]    [Pg.6]    [Pg.154]    [Pg.48]    [Pg.2]    [Pg.187]    [Pg.1100]    [Pg.1062]    [Pg.386]    [Pg.352]    [Pg.18]   
See also in sourсe #XX -- [ Pg.238 ]



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