Selective measurement of H- H scalar couplings from crowded chemical shift regions: Combined pure shift and spin-echo modulation approach.

J scalar couplings carry rich structural information and their measurements are fundamental in the H NMR based elucidation of small and medium molecules, which, however, are hampered in the presence of large J-coupling network. Further, enhanced spectral resolution is often essential for precise determination of a specific set of H- H J-couplings among the complex J-multiplets. In the light of the recent advancements in homodecoupling pure shift strategies, here, we report absorption mode, band-selective refocused pure shift spin-echo method, which helps in determining H- H J-couplings from crowded spectral regions. The importance of the present band-selective refocused pure shift spin-echo experiment is exemplified for 2 steroid molecules, estradiol and testosterone.