Alkaloids from Strychnos usambarensis: Revised structure for usambarine

Synthesis of (±)‐Strychnofoline via a Highly Convergent Selective Annulation Reaction

“…The combined organic solvents were washed with brine (20 mL), dried over anhydrous Na 2 SO 4 , filtered, and concentrated under reduced pressure. Purification by flash chromatography on silica gel (CH 2 + . + .…”

“…Aqueous HCl (1 m in H 2 O, 5 mL) was added and the reaction mixture was stirred for 5 min. The organic layer was separated and washed with saturated aqueous NaHCO 3 (10 mL) and brine (10 mL), dried over anhydrous Na 2 + . "First number/second number" in the 13 C NMR spectrum of 36 means that there are two small peaks belonging to one C, due to a slow equilibrium of rotamers during the measurement because of the Boc-protecting group on the lactam moiety.…”

“…After dilution with Et 2 O (150 mL) and H 2 O (100 mL), the combined organic solvents were filtered through a plug of silica gel. The filtrate was separated, washed with brine (10 mL), dried over anhydrous Na 2 + .…”

“…[2] The compound was shown to inhibit mitosis [3] in a number of cancer cell lines, including mouse melanoma B16, Ehrlich, and Hepatom HW165. A prominent structural feature of the oxindole alkaloids of the Strychnos family and related natural products is the presence of a spiro[pyrrolidin-3,3'-oxindole] core ( Figure 1).…”

Novel Routes to Pyrroles, Indoles and Carbazoles - Applications in Natural Product Synthesis

“…Later on Scheme 6. demethoxycarbonyldihydrogambirtannine was isolated from other natural sources. It was identified as the main alkaloid of the fruits of Strychnos usambarensis, a plant belonging to the family Loganiaceae found in Africa [34]. The consumption of these fruits causes poisoning.…”