It has empirical formula C 20 H 25 NO 3 and a melting point of 249-250 �C . The structure was determined to be a hetisine type diterpene by noting infrared spectrum absorption bands of 3405 cm " 1 ( OH ), 1718 ( C = O ), and 1650 ( C = C ), a proton magnetic resonance spectrum with " secondary ethyl, and methoxy groups . " Additional ultraviolet spectrum and carbon-13 NMR data, confirmed by high resolution mass spectrometry, completed the determination of the structure.
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