Synthesis and structure elucidation of a series of pyranochromene chalcones and flavanones using 1D and 2D NMR spectroscopy and X‐ray crystallography

A series of novel pyranochromene chalcones and corresponding flavanones were synthesized. This is the first report on the confirmation of the absolute configuration of chromene‐based flavanones using X‐ray crystallography. These compounds were characterized by 2D NMR spectroscopy, and their assignments are reported herein. The 3D structure of the chalcone 3b and flavanone 4g was determined by X‐ray crystallography, and the structure of the flavanone was confirmed to be in the S configuration at C‐2. Copyright © 2014 John Wiley & Sons, Ltd.