Structural confirmation of spiroelliptin from Iryanthera elliptica by synthesis

Spiroelliptin, a spiro[cyclohexadienone-1,1′-tetralin] from Iryanthera elliptica, was synthesized by a novel process which involved the catalytic hydrogenation of the appropriate chalcone. This and other spiro[methoxycyclobexadienone-1,1′-tetralin] derivatives, obtained by the same process or by the oxidative coupling of the appropriate 1,3-diarylpropanes, were used as models in the compilation of ¹H and ¹³C NMR data allowing the recognition of three such naturally occurring structural types.     

(—)-Rubranine from Aniba rosaeodora

Aniba rosaeodora wood was shown to contain (—)-rubranine. An optically inactive form of this citrylidene-chalcone was previously considered to be an artifact of extraction. The constitution of rubranine was confirmed by pyrolysis and syntheses, involving previously reported pyridine-catalysed condensation of pinocembrin and citral, whereby novel intermediates were prepared, and the acid-catalysed condensation of pinocembrin with geraniol followed by oxidation.     

Piplartine-dimer A,a new alkaloid from Piper tuberculatum

Piplartine-dimer A (1), a dimer of the known pyridone alkaloid piplartine, was isolated from root bark of Piper tuberculatum. It is accompanied by piplartine (3) and 3,4,5-trimethoxycinnamic acid.