Pimolin (1), a novel dimer of the furochromone, visnagin, has been isolated from the chloroform extracts of the seeds of the plant, Pimpinella monoica. Its structure as elucidated by multidimentional 1H and 13C nmr spectroscopy via. long range coupling (COLOC and COSYLR), indicated 2+2 pyrone-furan cycloaddition.
P. Pradhan, Luthria, D. L., and Banerji, A., “Pimolin, a new class of natural product from Pimpinella monoica : A novel dimeric furochromone”, Bioorganic & Medicinal Chemistry Letters, vol. 4, pp. 2425–2428, 1994.