Synthesis of Two Natural Furan-Cyclized Diarylheptanoids via 2-Furaldehyde

Two natural diarylheptanoids, 2-benzyl-5-(2-phenylethyl)furan (1) and 2-methoxy-4-{[5-(2-phenylethyl)furan-2-yl]methyl}phenol (2), were synthesized starting from 2-furaldehyde. A Wittig reaction of 2-furaldehyde with benzyltriphenylphosphonium bromide followed by reduction of the alkene CC bond with Mg gave 2-(2-phenylethyl)furan (5). Lithiation of 5 with BuLi at -78 degrees followed by alkylation with benzyl bromide gave natural product 1. In another approach, FriedelCrafts acylation of compound 5 with benzoyl chloride followed by deoxygenation of the CO group afforded 1. The natural product 2 was also synthesized by acylation of 5 with 4-acetoxy-3-methoxybenzoyl chloride (16) followed by deoxygenation and deacetylation.