Camaldulensals A-C, the First Meroterpenoids Possessing Two Spatially Separated Formyl Phloroglucinols Conjugated to a Terpene Core from the Leaves of Eucalyptus camaldulensis Dehnh

Threenew bis-formyl phloroglucinol-meroterpenoids(1-3), three new euglobal type formylphloroglucinol-meroterpenoids(4-6), and one new dimeric formylphloroglucinol (7) were isolated from the leaves of Eucalyptus camaldulensis. Camaldulensal A (1) is the first bis-isovaleryl-formyl-phloroglucinol-sesquiterpenoid.It features a novel 6/6/10/3/6/6 fused ring system and contains sixstereogenic centers. Camaldulensals B (2) and C (3) are the first bis-isovaleryl-formyl-phloroglucinols, eachconjugated to a monoterpene. Formyl phloroglucinol compounds (FPCs)containing two spatially separated formyl phloroglucinols conjugatedto a terpene core such as 1-3 havenot been reported previously. The structures of these compounds wereelucidated by spectroscopic methods and computational analysis. CamaldulensalsB (2) and C (3) exhibited significant antibacterialactivity against methicillin-susceptible and methicillin-resistant Staphylococcus aureus. Structure activity relationshipsare discussed in relation to previously reported antibacterial activitiesof other molecules from the FPC structure class.

Automated summary

Three new bis-formyl phloroglucinol-meroterpenoids (1-3), three new euglobal type formylphloroglucinol-meroterpenoids (4-6), and one new dimeric formylphloroglucinol (7) were isolated from Eucalyptus camaldulensis leaves. Camaldulensal A (1) is the first bis-isovaleryl-formyl-phloroglucinol-sesquiterpenoid with a unique fused ring system and six stereogenic centers. Camaldulensals B (2) and C (3) are the first bis-isovaleryl-formyl-phloroglucinols conjugated to a monoterpene. The compounds showed significant antibacterial activity against methicillin-susceptible and methicillin-resistant Staphylococcus aureus strains.