Abstract
The absolute configuration of phantasmidine was assigned by analysis of the two conformers of the two Mosher amides. The expected shielding of the protons adjacent to the nitrogen and large long range shielding (~1 ppm) of the cyclobutane methylene protons in 16major and the pyridine protons of 16minor by the phenyl group of the Mosher amide allows the assignment of absolute configuration as shown in Schemes 4 and 5.