Total synthesis of (-)-denticulatins A and B using efficient methods of acyclic stereocontrol
The total synthesis of (-)-denticulatin B (2) was achieved in 9 steps (20% yield), with 70% overall diastereoselectivity, starting from the ethyl ketone (R)-9. Most of the stereochemistry was introduced by substrate-based control. Key steps include the boron-mediated aldol/reduction, 9 → 22, the titanium-mediated aldol-coupling. 26 + 8 → 38, and the directed cyclisation, 35 → 2. Epimerisation at C10 in 35 led to (-)-denticulatin A (1).
Studies in Polypropionate Synthesis: Stereoselective Synthesis of (-)-Denticulatins A and B.
(-)-Denticulatin B (2) was prepared in 9 steps (20percent yield) with 70percent overall ds starting from the ethyl ketone (R)-8.Key steps are the novel boron-mediated aldol/reduction, 8 -> 12, the titanium aldol coupling, 6 + 5 -> 18, and the HF-pyridine cyclisation, 20 -> 2.Epimerisation at C10 in 20 led to (-)-denticulatin A (1).