Four new fawcettimine-related alkaloids from Phlegmariurus squarrosus

Four new fawcettimine-related alkaloids (1–4), together with 17 known ones, were isolated from club moss Phlegmariurus squarrosus. Notably, compound 1 was the derivative of lycoflexine with an unprecedented additional methyl group at C-17. Their structures were determined by extensive spectroscopic analysis, including 1D and 2D NMR, and HR-MS, as well as by comparison with the literature data. All new compounds were tested for their β-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) and acetylcholinesterase (AChE) inhibitory activities.