Bioinspired Total Synthesis of Hyperireflexolides A and B.

Hyperireflexolides A and B were synthesized in six steps via the dearomatization and fragmentation of a simple acylphloroglucinol starting material. The dearomatized acylphloroglucinol undergoes a sequence of oxidative radical cyclization, retro-Dieckmann fragmentation, stereodivergent intramolecular carbonyl-ene reactions, and final α-hydroxy-ß-diketone rearrangements to give the target natural products. This sequence is based on a biosynthetic proposal that claims the hyperireflexolides as highly rearranged polycyclic polyprenylated acylphloroglucinols (PPAPs), which is supported by the structural revision of hyperireflexolide B.

Intramolecular Tricarbonyl-Ene Reactions and α-Hydroxy-ß-Diketone Rearrangements Inspired by the Biosynthesis of Polycyclic Polyprenylated Acylphloroglucinols.

Structurally unique natural products pose biosynthetic puzzles whose solution can inspire new chemical reactions. Herein, we propose a unified biosynthetic pathway towards some complex meroterpenoids-the hyperireflexolides, biyoulactones, hybeanones and hypermonones. This hypothesis led to the discovery of uncatalyzed, intramolecular carbonyl-ene reactions that are spontaneous at room temperature. We also developed an anionic cascade reaction featuring an α-hydroxy-ß-diketone rearrangement and an intramolecular aldol reaction to access four distinct natural product scaffolds from a common intermediate.

Total Synthesis and Biosynthesis of Cyclodepsipeptide Cochinmicin I.

Phenylglycines are building blocks of many non-ribosomally synthesized peptides. The dihydroxyphenylglycine-containing cyclodepsipeptide cochinmicin I exhibits endothelin receptor antagonist activity. Therefore, it represents an interesting and synthetically challenging molecule because of the racemization-prone nature of dihydroxyphenylglycine. We present the total synthesis of cochinmicin I and the non-natural derivative cochinmicin VI and describe the identification and assignment of the cochinmicin (cmn) biosynthesis gene cluster, encoding a five-module non-ribosomal peptide synthetase for cochinmicin assembly.