Stereochemical Elucidation of Norbornene Derivatives Synthesized as Leukotriene D4 Receptor Antagonists

The complete H-1 and C-13 NMR assignment and stereochemical elucidation,of four norbornene derivatives (1-4) are presented. These derivatives were obtained by an asymmetric Diels-Alder reaction of a chiral dienophile, from D-glucose, as leukotriene D4 receptor antagonists. NOE measurements of the four products between H-7b and H-5 readily allowed discrimination between exo- (2, 4) and endo- (1, 3) diastercomers with respect to methyl carboxylate and tetrahydrofuro [1,3]dioxolyl groups. Further discrimination and subsequent absolute configuration determination of the two endo- and,two exo- products were performed by NOE peak measurements and molecular modeling calculations of relative interproton distances of the most stable conformations of each isomer.