Isolation and biomimetic synthesis of (±)-calliviminones A and B, two novel Diels–Alder adducts, from Callistemon viminalis

Antiplasmodial phloroglucinol derivatives from Syncarpia glomulifera

“…The first examples of such carbon Diels-Alder adducts between a phloroglucinol and a terpenoid were (±)-calliviminones A and B, isolated from Callistemon viminalis . 17 Compound 2 exhibited moderate antiplasmodial activity (IC 50 3.81 ± 1.14 µM), which is the first reported antiplasmodial activity of a phloroglucinol with the spiro-[5,5]-undec-8-ene skeleton. Compound 2 did not show any toxicity to HEK cells up to the highest dose tested (100 µM).…”

“…Compound 2 was a racemate at C-11 based on its zero optical rotation, and its structure was thus elucidated as (±)-2,2,4,4-tetramethyl-11-isobutyl-9-(4-methyl-3-penten-1-yl)- spiro[5.5]undec-8-ene -1,3,5-trione, and named as (±)-calliviminone C, based on its similar structure to (±)-calliviminones A and B. 17 …”

Callistemenonone A, a novel dearomatic dibenzofuran-type acylphloroglucinol with antimicrobial activity from Callistemon viminalis

“…Compound 1 might be an equimolar mixture of the two enantiomers based on its zero optical rotation value 10 . The relative configuration of 1 was deduced from an analysis of the ROESY correlations (Fig.…”

“…Although the HMBC experiment failed to provide direct and conclusive evidence for the linkage between the structural fragments I and II due to the absence of a suitable correlative proton, assembly of the two moieties was achieved through a connection of C-1-O-C-3′ which led to the presence of a furan ring and, together with portions I and II , accounted for the nine double bond equivalents. Compound 1 might be an equimolar mixture of the two enantiomers based on its zero optical rotation value 10 . The relative configuration of 1 was deduced from an analysis of the ROESY correlations (Fig.…”

“…Plants in the genus Callistemon are known for their enriched phloroglucinol content, which is responsible for a variety of the biological activities of these herbal medicines 4 , 5 . Previous phytochemical studies on different parts of C. viminalis showed the presence of flavonoids 9 , triterpenoids 9 , tannins, and phloroglucinol derivatives 10 , 11 . In a continuation of our efforts to discover new antibacterial constituents from the plants of family Myrtaceae 12 – 17 , the ethanolic extract of C. viminalis was found to exhibit in vitro antibacterial activity with a MIC value of 100 μg/mL against MRSA JCSC 2172.…”