Chemical Constituents of Alnus  sieboldiana (BETULACEAE). III. The Synthesis and Stereochemistry of Yashabushiketols

Abstract Dihydroyashabushiketol (2), isolated previously from the male flower of Alnus sieboldiana, has been synthesized by the condensation of benzaldehyde with acetylacetone, followed by hydrogenation. The absolute configuration at C5 of yashabushiketol (1) and 2 has been identified as S. The geometry between the trans double bond and the carbonyl group in 1 was established to be s-cis. Eleven more minor components of a known aromatic compound were identified at the same time.