Acremolin, Structural Revision of a Purported 1H-Azirine-Containing Natural Product

Acremolin, a modified nucleobase isolated from the marine fungus Acremonium strictum, was claimed to have the structure 1; the first example of a natural product to possess a 1H-azirine moiety.¹ Based on the spectroscopic data reported for acremolin, we proposed a revised structure 2 for the natural product that guided a rational five-step total synthesis. The etheno-guanine 2, prepared from guanosine and fully characterized by spectroscopic methods including ¹H-¹³C and ¹H-¹⁵N HMBC, had identical ¹H and ¹³C NMR data to those of natural acremolin, contradicting the original 1H-azirine structure 1. Additional properties of acremolin (2) will be disclosed.

Reference: [1] Julianti, E.; Oh, H.; Lee, H.; Oh, D.; Oh, K.; Shin, J. Tetrahedron Lett. 2012, 53, 2885 – 2886