Indole alkaloids from Vinca erecta type of sarpagine and ajmaline

The single crystal X-ray diffraction method established the absolute configuration of the Vinca erecta indole alkaloids of the akuammidine sarpagine type (3 S , 5 S , 15 R , 16 R ) and its o-acyl derivative, as well as the type of ajmaline, quebrachidine (2 S , 3 S , 5 S, 7 R , 15 S , 16 R , 17 S ) and majoridine (2 R , 3 S , 5 S , 7 R , 15 R , 16 S , 17 R ). Crystal data for C 21 H 24 N 2 O 3 ( 1 ): orthorhombic, space group P2 1 2 1 2 1 (no. 19), a  = 6.3949(5) A, b  = 13.5009(10) A, c  = 22.461(3) A, Z  = 4, 7694 reflections measured (7.64° ≤ 2Θ ≤ 152.294°), 3813 unique ( R int = 0.0798) which were used in all calculations. The final R 1 was 0.0680 (I > 2σ(I)) and wR 2 was 0.1650 (all data). Crystal data for C 23 H 26 N 2 O 4 ( 2 ): orthorhombic, space group P2 1 2 1 2 1 (no. 19), a  = 9.9730(13) A, b  = 10.2090(10) A, c  = 20.409(3) A, Z  = 4, 7959 reflections measured (8.666° ≤ 2Θ ≤ 151.998°), 4212 unique ( R int = 0.0386) which were used in all calculations. The final R 1 was 0.0477 (I > 2σ(I)) and wR 2 was 0.1171 (all data). Crystal data for C 42 H 48 N 4 O 6 ( 3 ): monoclinic, space group P2 1 (no. 4), a  = 8.9320(10) A, b  = 21.515(5) A, c  = 9.5420(10) A, β  = 97.103(10)°, Z  = 2, 16677 reflections measured (9.34° ≤ 2Θ ≤ 151.836°), 7393 unique ( R int = 0.0278) which were used in all calculations. The final R 1 was 0.0366 (I > 2σ(I)) and wR 2 was 0.1037 (all data). Crystal data for C 23 H 28 N 2 O 3 ( 4 ): orthorhombic, space group P2 1 2 1 2 1 (no. 19), a  = 10.636(2) A, b  = 11.208(12) A, c  = 16.725(13) A, Z  = 4, 1650 reflections measured (9.498° ≤ 2Θ ≤ 119.97°), 1650 unique ( R int = 0.0436) which were used in all calculations. The final R 1 was 0.0608 (I > 2σ(I)) and wR 2 was 0.1720 (all data). In alkaloids such as sarpagine and ajmaline exo, the substituents of alkaloids do not lead to conformational changes of a stable polycyclic framework. In the series of sarpagine, alkaloids form mono-salts in the tetrahedral nitrogen N4, and in indolines of the ajmaline type, the tetrahedral hybridization of the N1 and N4 atoms favors the formation of disols. In V. erecta alkaloids, the exomethylene fragment (C18-C19=C20-C21) of the polycyclic backbone always takes on the E-state.