Rogersonins C-F, 9H-Imidazo[2,1-i]purine-Incorporating Adenine-Polyketide Hybrids from an Ophiocordyceps-Associated Clonostachys rogersoniana.

ABSTRACT

Rogersonins C-F (1-4), four unprecedented adenine-polyketide hybrids featuring a rare 9H-imidazo[2,1-i]purine (1,N6-ethenoadenine) moiety, were isolated from an Ophiocordyceps-associated fungus, Clonostachys rogersoniana. Their structures were elucidated primarily by NMR experiments. The absolute configurations of 1-4 were assigned by a combination of the modified Mosher method, chemical degradation, electronic circular dichroism (ECD) calculations, and X-ray crystallography using Cu Kα radiation. Compound 3 downregulated the expression of PD-L1 protein in MDA-MB-231 and A549 cells, but did not show detectable effect on mRNA transcription of the PD-L1-encoding gene CD274.