Bioinspired First Stereoselective Total Synthesis of Spinosulfate B

Alkyl aromatic derivatives from the endophytic fungus Cytospora rhizophorae

Two new alkylresorcinols named herein 5'-methoxy-integracins A-B (1-2), two new monomeric alkyl aromatic derivatives 3-(7-hydroxyheptyl)-5-methoxyphenol (5) and 7-(3,5-dihydroxyphenyl) heptyl acetate (6), along with four known compounds including integracins A-B (3-4), 2,4-dihydroxy-6-(8-hydroxyoctyl) benzene (7), and cytosporone B (8) were isolated from the endophytic fungus Cytospora rhizophorae A761. The structures of the four new compounds were elucidated by NMR, HRESIMS data, and electronic circular dichroism (ECD) calculations, whereas the compounds 1 and 2 were disclosed as a class of the natural rare-occurring dimeric alkylresorcinol derivatives. Moreover, the bioassays of the new compounds clarified that compound 1 was a potent inhibitor for the α-glucosidase, and compound 2 showed relatively good activity against the tumor cell lines. It is worth mentioning that the known compound integracin B (4) was first reported to display significant antibacterial activity against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) with MIC values of 6.25 μg ml^-1.

Formal Synthesis of (-)-Haliclonin A: Stereoselective Construction of an Azabicyclo[3.3.1]nonane Ring System by a Tandem Radical Reaction

A formal synthesis of (-)-haliclonin A, isolated from the marine sponge Haliclona sp. in Korea, is described. The key feature of the synthesis includes the highly stereoselective tandem radical reaction to construct the azabicyclo[3.3.1]nonane core and the enantioselective formation of an all-carbon quaternary center via the Pd-mediated deracemization.