Figure 4.

HPLC-SPE-NMR-based long-range shift correlation (HMBC) NMR spectrum of M16 (2β-OH VD) recorded in CD₃CN at 300K. Experimental conditions: pulse program hmbcgplpndqf; 2K data points in the ¹H domain, 256 increments in the ¹³C domain, zero filled to 1K. Recording of 96 transients per increment, acquisition time 11.5 h. The C-H correlation signals not only allowed for connection of the individual proton networks of the H-H correlation pattern derivable substructures, but also for unequivocal placement t of metabolic oxidation at the carbon position C2.