Three new Urea derivatives from Pliocene-fossil Pinus armandii

Three new urea derivatives, isolated from the Pliocene lignified wood of Pinus armandii, were identified as carbonylbis[imino(6-methyl-3,1-phenylene)]bis[carbamic acid] dimethyl ester (1), and as the corresponding dibutyl ester 2 and bis(2-methylpropyl) ester 3. Their structures were elucidated by spectroscopic methods, including MS and 1D- and 2D-NMR techniques.