Obscurinin A, a unique Lycopodium alkaloid possessing an 8/6/6/6/5 pentacyclic system isolated from Lycopodium obscurum L.

Abstract

Obscurinin A (1), an unprecedented Lycopodium alkaloid featuring an 8/6/6/6/5 ring system, was isolated from the methanol extract of Lycopodium obscurum L. This novel skeleton possessed a fused 2-methyl-9-aza-tetracyclo[7.5.1.1^4,14.0^5,15]hexadecane core with a 2-oxazolidinone moiety. Its structure was assigned by spectroscopic and single-crystal X-ray diffraction data. A biological study showed that compound 1 exhibited significant inhibitory activity on the Ca_v3.1 calcium channel with an IC₅₀ value of 12.00 ± 0.35 μM.