Manginoids A-G: Seven Monoterpene-Shikimate-Conjugated Meroterpenoids with a Spiro Ring System from Guignardia mangiferae.

Manginoids A-G (1-7), seven monoterpene-shikimate-conjugated meroterpenoids with a spiro ring system, were isolated from Guignardia mangiferae. Compounds 1-4 are four isomers with epimeric and double-bond isomeric features possessing a 6-oxaspiro[bicyclo[3.2.1]octane-3,5'-indene] ring, which represent the first examples of spiro meroterpenoids bearing a bridged spirocyclohexanedione moiety. Compounds 5 and 6 possess an unexpected 2,4-dioxatricyclo[3.3.1.03,7]nonane motif, which fuses with a 6-oxabicyclo[3.2.1]octane moiety. Compound 1 exhibits inhibitory activities against 11β-hydroxysteroid dehydrogenase type 1 with an IC50 value of 0.84 μM.