CONFORMATIONAL-ANALYSIS OF TETRAHYDROFUROFURAN LIGNANS - SESAMOLIN

The stereochemistry of sesamolin (1), an aryl-aryloxy-tetrahydro-furof uran derivative comprising a main component of the lignans isolated fr om Sesamum indicum, was investigated. The favoured conformation was de termined using several methods of conformational analysis: nuclear Ove rhauser effect (NOE), lanthanide induced shifts (H-1-LIS), molecular m echanics (force-field) calculations (FF), and X-ray crystal structure determination. The conformation was found to deviate from the more com mon analoguous diaryltetrahydrofurofuran derivatives. The reason is th e anomeric effect of the cyclic acetal favouring a pseudo-axial positi on of the aryloxy substituent.