Kagimminols
A (1) and B (2), new cembrene-type
diterpenoids, were isolated from an Okeania sp. marine
cyanobacterium. By combining DP4 analysis with an efficient NMR chemical
shift calculation protocol, we clarified the relative configurations
of 1 and 2 without consuming precious natural
products. We determined the absolute configurations by a comparison
of theoretical electronic circular dichroism (ECD) spectra with experimental
spectra, and the absolute configuration of 1 was verified
experimentally. Finally, we found that 1 and 2 showed selective growth-inhibitory activity against the causative
agent of human African trypanosomiasis. This study exemplifies that
computational chemistry is an efficient tool for clarifying the configurations
of natural products possessing tautomers in equilibrium.