Total Synthesis of the Proposed Structure of Trichodermatide A
摘要:
A short total synthesis of the published structure of racemic trichodermatide A is reported. Our synthesis involves a Knoevenagel condensation/Michael addition sequence, followed by the formation of tricyclic hexahydroxanthene-dione and a diastereoselective bis-hydroxylation. The final product, the structure of which was confirmed by X-ray crystallography, has NMR spectra that are very similar, but not identical, to those of the isolated natural product. Quantum chemically computed C-13 shifts agree well with the present NMR measurements.
Hard core made easy: The pentacyclic core of trichodermatide A was stereoselectively synthesized from a bis(1,3‐cyclohexanedione) derivative by a ring‐closing reaction followed by an intramolecular ketal formation (see scheme; PPTS=pyridinium p‐toluenesulfonate). The first total synthesis of trichodermatide A was then completed by the introduction of three hydroxy groups.