Alkaloide aus Schizozygia caffaeoides (BOJ.) BAILL. II. Die Struktur des Schizozygins

Abstract

From chemical degradation experiments and spectroscopical data structure I is deduced for schizozygine, the major alkaloid of Schizozygia caffaeoides (BOJ.) BAILL. The given relative configuration is suggested by experiments indicating a strain‐free ring system.

Explorations on the total synthesis of (±)-isoschizogamine using an intramolecular 1,4-dipolar cycloaddition strategy

“…The filtrate was concentrated under reduced pressure and the residue was purified by flash column silica gel chromatography to provide 0.57 g (62%) of methyl 2-(diethoxyphosphoryl)-6-(4,5-dimethoxy-2-nitrophenyl)-hex- To a solution of 48 mg (0.082 mmol) of the above lactam in THF (1.5 mL) and MeOH (1.5 mL) at rt was added 9.0 mg (0.16 mmol) of NaOMe in one portion. After stirring at rt for 30 min, the reaction was diluted with Et 2 O, quenched by the addition of saturated aqueous NH 4 Cl, and extracted with Et 2 O. The combined organic extracts were dried over anhydrous MgSO 4 , filtered, and concentrated under reduced pressure provided the diester 42 which was used in the next step without purification.…”

“…To the above ring-opened diester in CH 3 CN (3 mL) at rt was added 18 µL (0.12 mmol) of DBU. The reaction mixture was heated to reflux for 1 h. After cooling to rt, the reaction mixture was quenched by the addition of saturated aqueous NH 4 Cl and extracted with Et 2 O. The combined organic extracts were dried over anhydrous MgSO 4 , filtered, and concentrated under reduced pressure.…”

“…After stirring for 1 h at rt, the reaction was diluted with Et 2 O, quenched by the addition of saturated aqueous NaHCO 3 , and extracted with Et 2 O and EtOAc. The combined organic extracts were dried over anhydrous MgSO 4 , filtered, and concentrated under reduced pressure. Purification of the residue by preparative TLC on silica gel gave 13 mg (71%) of methyl 2-(3-(4-(4,5-dimethoxy-2-nitrophenyl)but-3-enyl)-2-oxo-1,2,3,6-tetrahydropyridin-3-yl)acetate (30) as an inseparable 2:1 mixture of Z:E alkene isomers.…”

“…2,3 In addition to the major alkaloid schizozygine (1), 4 a pair of minor alkaloids were isolated 5 and their structures were established as isoschizogaline (2) and isoschizogamine (3) on the basis of extensive NMR studies. 3 It was postulated that the skeleton of the schizozyganes could be biogenetically derived from the Aspidosperma alkaloid family, and indeed both groups of alkaloids are found in the same plant species.…”

“…6 A proposed biosynthesis of the schizozyganes from the Aspidosperma alkaloids and further conversion to the isoschizozyganes was initially proposed by Hájíček 7 and this is shown in Scheme 1. An acid catalyzed rearrangement of the aspidosperma skeleton (4) results in the ring-opened schizozygane skeleton 6 via intermediate 5. Alternatively, oxidation of 5 would lead to a transient iminium ion intermediate 7.…”