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Abstract Massarinolin A and purpurolides are bioactive bergamotane sesquiterpenes condensed with a variety of synthetically challenging ring systems: a bicyclo[3.1.1]heptane, an oxaspiro[3.4]octane, and a dioxaspiro[4.4]nonane (oxaspirolactone). Herein, we report the first enantioselective total syntheses of massarinolin A, purpurolides B, D, E, and 2,3‐deoxypurpurolide C. Our synthesis and computational analysis also led to a structural revision of massarinolin A. The divergent approach features an enantioselective organocatalyzed Diels–Alder reaction to install the first stereogenic center in highee, a scalable flow photochemical Wolff rearrangement to build the key bicyclo[3.1.1]heptane, a furan oxidative cyclization to form the oxaspirolactone, a late‐stage allylic C−H oxidation, and a Myers’ NBSH‐promoted sigmatropic elimination to install theexomethylene group of massarinolin A.
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Total Synthesis of Cyanobactin Natural Product Balgacyclamide B
Abstract Balgacyclamide A−C are a family of cyanobactin natural products isolated from freshwater cyanobacteriaMicrocystis aeruginosa. These macrocyclic peptides are characterized by their oxazoline‐thiazole core, their 7 or 8 stereocenters, and their antiparasitic activities. Balgacyclamide B is known for its activity towardsPlasmodium falciparumchloroquine‐resistant strain K1,Trypanosoma brucei rhodesiense, andLeishmania donovani. In this report, the first total synthesis of Balgacyclamide B is described in a 17‐steps pathway and a 2 % overall yield. The synthetic pathway toward balgacyclamide B can be adapted for the future syntheses of balgacyclamide A and C. In addition, a brief history background of oxazolines syntheses is shown to emphasize the importance of the cyclization conditions used to interconvert or retain configuration of β‐hydroxy amides via dehydrative cyclization.
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- Award ID(s):
- 1848186
- PAR ID:
- 10475309
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 30
- Issue:
- 3
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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