Total Synthesis and Structural Reassignment of Aranorosinol A, Aranorosinol B, and EI-2128-1

Enantioselective Total Syntheses of (-)-Caulamidine D and (-)-Isocaulamidine D and Their Absolute Configuration Reassignment

The first enantioselective total syntheses of (-)-caulamidine D (5) and (-)-isocaulamidine D (6) were accomplished. Their absolute configurations were unambiguously elucidated through X-ray crystallography. The isolated natural samples of both 5 and 6 are determined to be the TFA salts instead of the neutral forms. It took 16 steps (longest linear sequence) to divergently access both 5 and 6 following a unified strategy. The key reactions include (1) development and application of an asymmetric Meerwein-Eschenmoser-Claisen rearrangement to construct the challenging C10, C23 consecutive stereocenters and (2) application of a cascade 6-exo-dig/6-exo-tet amine/nitrile cyclization reaction.

Chemical investigations into the biosynthesis of the gymnastatin and dankastatin alkaloids

Electrophilic natural products have provided fertile ground for understanding how nature inhibits protein function using covalent bond formation. The fungal strain Gymnascella dankaliensis has provided an especially interesting collection of halogenated cytotoxic agents derived from tyrosine which feature an array of reactive functional groups. Herein we explore chemical and potentially biosynthetic relationships between architecturally complex gymnastatin and dankastatin members, finding conditions that favor formation of a given scaffold from a common intermediate. Additionally, we find that multiple natural products can also be formed from aranorosin, a non-halogenated natural product also produced by Gymnascella sp. fungi, using simple chloride salts thus offering an alternative hypothesis for the origins of these compounds in nature. Finally, growth inhibitory activity of multiple members against human triple negative breast cancer cells is reported.

Total synthesis sheds light on biosynthetic relationships among the chlorinated gymnastatin and dankastatin alkaloids.

Antibacterial kaneoheoic acids A-F from a Hawaiian fungus Fusarium sp. FM701

Alarming rate of resistance to the existing antibiotics exhibits the importance of developing new antibiotic molecules from relatively under explored sources as well as implementing alternative approaches like antibiotic adjuvants. Six previously undescribed fungal polyketides, kaneoheoic acids A-F (1-6) were isolated from a fungal strain Fusarium sp. FM701 which was collected from a muddy sample of Hawaiian beach. The structures of these six compounds were elucidated by spectroscopic interpretation, including HRESIMS and NMR, and electronic circular dichroism (ECD) analysis. All six compounds that were inactive when tested alone showed significant antibacterial activity against Staphylococcus aureus and Bacillus subtilis, in the range of 10-80 μg/mL when assayed in combination with either chloramphenicol (half of the MIC, 1 μg/mL), an FDA approved antibiotic or disulfiram (6 μg/mL), an established antibiotic adjuvant that augmented the activity of antibiotics.

Chemoselective Perfluoromethylation of Thio- and Selenoamides

A chemo- and regioselective perfluoromethylation using thioamides/selenoamides (prepared one step from corresponding lactams) as starting materials has been discovered. The reaction demonstrated complementary chemoselectivity to the C-H trifluoromethylation of (hetero)arenes as well as remarkable functional group compatibility especially toward radical sensitive olefin-, alkyne-, and arylhalide-bearing substrates. The examples of perfluorothio-/selenolated drug molecules indicated application potential of this strategy in drug modification and drug-analogue preparation.