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An unusual katsumadain dimer via a [2 + 2] cycloaddition, katsumadain C (1), and a unique chalcone-diarylheptanoid adduct via a Diels-Alder reaction, calyxin Y (2) with novel carbon frameworks, were isolated from the seeds of Alpinia katsumadai. Their structures and relative configurations were determined by spectroscopic evidence.
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Yang et al. (2011) studied this question.
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