Experimental and Density Functional Theory Study of a New Dimer with Tetrasubstituted Cyclobutane Ring System Isolated from Psoralea plicata Seeds

A new cyclobutane ring system related to plicatin B has been isolated from the methanol soluble fraction of Psoralea plicata seeds and named as -diplicatin B. In addition, the anti-repellent (-)-loliolide and phloretic acid ethyl ester [3-(4-hydroxyphenyl) propanoic acid ethyl ester) have been isolated from the same extract, their structures being determined on the basis of 1D ( 1 HNMR and 13 CNMR) and 2D (DQF-COSY, HMQC and HMBC) NMR and mass spectra. Stereoisomers of -diplactin B have been optimized by means of density functional theory using the hybrid functional B3LYP.