Total Synthesis of (−)-Denticulatins A and B Using Efficient Methods of Acyclic Stereocontrol.
作者:Ian Paterson、Michael V. Perkins
DOI:10.1016/0040-4020(95)01015-7
日期:1996.1
The totalsynthesis 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 substratebased 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
The first total synthesis of antibacterial epicoccarine A isolated from a fungus Epicoccum sp. has been accomplished in 10 steps along with synthetic elaboration of its C5-epimer, highlighting the utility of O- to C-acyl rearrangement of a 4-O-acyltetramic acid derivative. Comparison of spectroscopic properties and specific optical rotations of the synthetic samples with those reported for authentic material has clearly indicated the unspecified absolute stereochemistry of this natural product to be 5S.