m-Chloroperbenzoic acid → Catharanthine N-oxide

Beteiligte Stoffe

Reaktionsschritte

To a solution of catharanthine (Formula III, 200 mg, 0.6 mmol) in dry methylene chloride (2 ml) at −20° C. under a positive atmosphere of argon was added m-chloroperbenzoic acid (132 mg, 0.8 mmol), and the mixture was stirred for 5 minutes. To the catharanthine N-oxide (IIIa; R═COOCH3; R1, R2, R3, and R4=H), thus formed was added a solution of vindoline (IV, 270 mg, 0.6 mmol) in methylene chloride (1 ml) and the mixture was cooled to −60° C. Trifluoroacetic anhydride (0.2 ml, 1.5 mmol) was added to the stirred reaction mixture maintained at −60° C. for 2 hours. After this time, the solvent and excess reagents were removed in vacuo at −20° C. to leave a reddish-brown residue containing the iminium intermediate. The intermediate was characterized by reverse phase high performance liquid chromatography (HPLC) (Waters Radial-Pak C18 or CN cartridge, methanol-H2O-Et3N as solvent system). It was shown that the yield of the iminium intermediate of Formula VI in this reaction exceeded 80%.

Herkunft & Nachweise