Total Synthesis 5: (±)-Chloranthalactone A

Total Synthesis of (±)-Chloranthalactone A.

Chloranthalactone A belongs to a family of sesquiterpenoids. It possesses a novel polycyclic framework embedded with a sterically congested cyclopentane ring.

Synthesis steps:
1. Vinyl Michael addition followed by ketone protection with glycol.
2. Formation of Weinreb amide which is attacked by the in situ generated LiCH2OMOM.
3. Matteson epoxidation.
4. Treatment with lithium 2,2,6,6-tetramethylpiperidide (LTMP) generates the 3/5/6 tricyclic compound.
5. Global deprotection.
6. Formation of dioxolanethione.
7. Corey-Winter olefination reaction.
8. Aldol reaction with ethyl pyruvate.
9. Protection of the tertiary alcohol as an acetal.
10. DBU-promoted cyclization generates the final compound.

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