Characterization of Leptazolines A-D, Polar Oxazolines from the Cyanobacterium Leptolyngbya sp., Reveals a Glitch with the Willoughby-Hoye Scripts for Calculating NMR Chemical Shifts

The bioactivity-guided examination of a Leptolyngbya sp. led to the isolation of leptazolines A D (1-4), from the culture media, along with two degradation products (5 and 6). Density functional theory nuclear magnetic resonance calculations established the relative configurations of 1 and 2 and revealed that the calculated shifts depended on the operating system when using the Willoughby Hoye Python scripts to streamline the processing of the output files, a previously unrecognized flaw that could lead to incorrect conclusions.