Total synthesis of (±)-cyclopeltain B

Herein, we report the first total synthesis of (±)-cyclopeltain B, a structurally unique alkylated adenine derivative featuring a rare 6/5/7/5 fused ring system. The synthesis was accomplished using commercially available adenine and (Z)-but-2-ene-1,4-diol as starting materials. Key steps include an aza-Michael addition followed by a TiCl₄-mediated one-pot five-step cascade reaction to construct the complex (6/5/7/5) fused ring scaffold. The structure of the synthetic (±)-cyclopeltain B was confirmed by X-ray crystallographic analysis in addition to spectral data comparison with the natural product. Furthermore, a series of structurally related analogues was synthesised to evaluate their biological activities.