, Bubbialidine reported by Gademan and coworkers

, Jiang reported more recently the total synthesis of (-)-Norsecurinine, Niruroidine and dimeric alkaloid, vol.38, p.9

, steps with an overall yield of 12%. Interestingly, synthesis of (-)-Niruroidine was obtained for the first time in four chemical steps from (-)-Norsecurinine with 37% of overall yield

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, Colorless oil

, Procedure for the racemic synthesis of Virosine B and Virosine A starting from 352a. (±)-Virosine A and (±)-Virosine B: To a stirred solution of azide precursor 352a (0.18 g, 0.45 mmol) in argon-degassed ACN (9 mL) was added PPh 3 (0.59 g, 2.23 mmol) at room temperature. The mixture was stirred overnight at room temperature, and all volatiles were removed in vacuo. The resulting oil was dissolved in a THF/AcOH 1:1 mixture, Procedure for the synthesis of Securinega alkaloids of neosecurinine type Scheme 3.66

, and the reaction mixture was stirred another 30 minutes at room temperature, before water (10 mL) and brine (5 mL) were added to quench the reaction. Organic compound was extracted with EtOAc (6 x 10 mL) from the aqueous solution. The combined organic layers were dried over Na 2 SO 4 , and concentrated in vacuo. Filtration through a short pad of silica gel, eluting with Et 2 O/DCM/Petroleum ether (8:2:90 to 32:8:60), afforded the protected natural products as a mixture of diastereomers 358a and 358b (55:45 ratio). The resulting oil was dissolved in THF (9 mL) and transferred to a Teflon reactor

, 52 mL, 44.7 mmol) was added to quench the reaction. The resulting mixture

, Scheme 3.67. Staudinger aza-Wittig reaction afforded 5 membered stable imine 361-cis

C. Nmr, , p.75

, CDCl 3 ) ??(ppm) = 101.0, 86.1 (C-quaternary, Cp), vol.821, 1106.

, DMSO-d 6 ) ??(ppm) = 100.0, 86.1 (C-quaternary, Cp), p.92

, To a stirred solution of sodium bicarbonate (NaHCO 3 , 58 g, 0.69 mol, vol.0, p.27

, The resulting mixture was cooled down to 0 °C, and Oxone® (120 g, 0.195 mol, 0.15 mol KHSO 5 ) was added every two minutes in successive portions to avoid too much foaming. The ice bath was then removed, and the resulting solution was distilled under reduced pressure (ca. 20-30 mmHg) for 1 hour, the distillate being collected at ?78 °C, until no more distillation was observed. The distillate was stored at ?18 °C on 4 Å molecular sieves, water (254 mL) was added acetone (192 mL, 2.59 mol, 1.0 equiv.)

C. Bosset, R. Coffinier, P. A. Peixoto, M. El-assal, K. Miqueu et al., Angew. Chem., Int. Ed, vol.53, pp.9860-9864, 2014.

H. , , p.300

C. Nmr, , p.75

. Mhz,