Total Synthesis of Calystegine B₄

Abstract

Abstract The total synthesis of calystegine B 4 was achieved in 10 steps from (–)‐ D ‐lyxose by using a new synthetic strategy to obtain the requisite protected hydroxylated 4‐aminocyclohept‐2‐en‐1‐one without the problem of regioisomer formation that was a problem in the earlier synthesis of this natural product. The key steps included a Petasis–borono‐Mannich reaction and a ring‐closing metathesis reaction.