Four new dihydro‐β‐agarofurans, denhaminols K–N (4–7), along with three known secondary metabolites, denhaminols A–C (1–3) were obtained from the large‐scale isolation studies of the leaves of the Australian endemic rainforest plant, Denhamia celastroides. The structures of the previously undescribed compounds were determined by detailed 1D and 2D nuclear magnetic resonance spectroscopy, mass spectrometry, ultraviolet, and infrared data analysis. All compounds were found to inhibit the activity of leucine transport in a human prostate cancer cell line with IC50 values ranging from 5.1–74.9 μM. Dihydro‐β‐agarofurans 1–7 showed better potency than the L‐type amino acid transporter family inhibitor, 2‐aminobicyclo[2.2.1]‐heptane‐2‐carboxylic acid (BCH).