HCID 70639872, compound → Gambogic acid

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Reaction Steps

Gambogic acid (GA, CAS No. 2752-65-0) which was previously isolated as an inseparable stereomeric mixture of C-2 epimers, were separated into two epimers (gambogic acid and epigambogic acid, referred to as 1 and 2) according to the present invention. In the HPLC analysis, GA presented as one peak (m/z 628) on C18 column (Alltima C18, 5μ, 4.6×250 mm) eluted with CH3CN/0.1% acetic acid (90:10). When the fraction corresponding to the single peak was then subject to C8 column (Alltima C8, 5μ, 4.6×250 mm), eluted with CH3CN/0.1% acetic acid (75:25), two completely separated peaks appear. These two peaks were isolated by HPLC under the same analytical condition with each injection of 20 μL acetone solution of gambogic acid (35 mg/mL), yielding 1 (12 mg) and 2 (10 mg). The two peaks being two C-2 epimers of GA was clearly confirmed by extensive spectroscopic analysis and direct comparison of NMR and HPLC data with those of the known R-epimer. In addition, two similar pairs of C-2 epimeric xanthones were also isolated from this plant by the same method. They were identified to be isogambogic acid, epiisogambogic acid, 30-hydroxygambogic acid, and 30-hydroxyepigambogic acid by extensive spectroscopic and chromatographic analysis including HRMS, 2D NMR, and HPLC techniques. All of these epimers except gambogic acid (R-epimer which had been reported by American scientists using single crystal X-ray diffraction) were isolated and separated for the first time, and 30-hydroxygambogic acid and 30-hydroxyepigambogic acid were previously unknown compounds.

Provenance & Evidence