Bicyclo[3.2.1]octane and 6-oxabicyclo[3.2.2]nonane type neolignans from Magnolia denudata

From the ethyl acetate soluble fraction of twigs of Magnolia denudata (Magn oliaceae), seven new neolignan derivatives, 1-7, were isolated along with e ighteen known lignan and neolignan derivatives, 8-25, The structures of the new neolignans were elucidated by means of spectral methods, especially bq H-1-NMR and C-13-NMR spectra, and two dimensional NMR methods such as H-1- detected heteronuculear multiple bond connectivity (HMBC), H-1-detected mul tiple quantum coherence (HMQC) and H-1-H-1-correlation spectroscopy (COSY). Compounds 1-4 have novel structures possessing a 6-oxabicyclo[3.2.2]nonane skeleton and compounds 5-8 also have novel structures possessing a bicyclo [3.2.1]octane skeleton. The anti-platelet-activating factor (PAF) activity of these compounds was tested by measurement of inhibition activity against acetyl transferase to lyso-PAF.