Onitin and onitisin, new phenolic pterosins from the fern

Total Synthesis of Onitin

“…24,25 Acid-catalyzed pinacol−pinacolone-type rearrangement of compound 12 afforded aldehyde 3 in 80% yield (Scheme 4). Demethylation of 3 followed by chemoselective reduction completed the total synthesis of onitin (1). The NMR spectroscopic data of synthesized onitin (1) were in full agreement with the literature data.…”

“…The synthesized products were purified by column chromatography using silica gel (100−200 mesh). 1 H NMR (300, 400 MHz) and 13 C NMR (100 MHz) spectra were recorded on 300 and 400 MHz Bruker-AVANCE spectrometers in CDCl 3 , methanol-d 4 , and DMSO-d 6 with TMS as internal standard (for CDCl 3 ). The HRMS data were recorded on an LC QTOF spectrometer (ESI).…”

“…The reaction was quenched with water, extracted with EtOAc, and purified by column chromatography to give compound 4 as a light yellow liquid (0.420 g, 90.3%). 1 H NMR (400 MHz, CDCl 3 ) δ 6.63 (1H, dd, J = 23.9 Hz, 15.2 Hz), 5.62 (1H, dd, J = 15.2 Hz, 2.6 Hz), 5.22 (1H, dd, J = 23.9 Hz, 2.6 Hz), 3 (7-Methoxy-2,2,4,6-tetramethyl-3-oxoindan-5-yl)acetaldehyde (3) and 6-Acetyl-4-methoxy-2,2,5,7-tetramethylindan-1-one (8). Preheated t-BuOH at 85 °C was added to a mixture of compound 4 (0.580 g, 2.377 mmol) and benzoquinone (0.295 g, 2.733 mmol, 115 mol %).…”

“…Among these natural products, onitin was the first phenolic sesquiterpenoid isolated from Onychium auratum. 1 It is an illudalane class of sesquiterpenoid, having a highly functionalized indanone nucleus. Extracts from the herb Onychium have been used in Taiwanese folk medicine as an antidiarrheic agent.…”

“…12,13 Recently, we have reported the total synthesis of coprinol. 14 Herein, we report a synthetic route (nine steps) to onitin (1).…”