Über Umwandlungen der Iboga‐Alkaloide Voacangin und Conopharyngin 154. Mitteilung über Alkaloide

Abstract

211 Experimental Part. -The mass spcctruni of discretaminc WLS deterrnincd with a CEC 21-110 B m a s spectrometcr (70 CV ionizing encrgy, 180v soiirce tcmperaturc, direct saniplc insertion). 'The authors wish t o thank l>r. J. Schmutz, Ftirschungsinstitut Dr. A . Wander AG, Bern, Switzcrland, for the gencrous gift of thc remainder of his cliscrctaminc satnplc. (18. XI. 74)Summauy. The reduction products voacaiiginol (3) arid coriopharynginol (4), obtaincd from thc indolc alkaloids voacanginc (1) and ctmopharynginc (2) rc!qx:ctivcly, gave, by the trcatmcnt of theit tosylatcs 5 und 6 with tricthylaminct, two fragmrnt:itioti pr'oducts, voaenamine (7) (70-80%) and conoenatnine (8) (2545%) respectively (Schemr. I). The structures of 7 and 8 were derived from spcctroscoyic evidence and some chcrtiical translormations.Conopharynginol tosylatc (6) gave with tcrtiary basc, Ix:sides 8, thc quatcrnary aziridinium salt 12 (58%) (Scheme 3). This salt could undcrgo nuclcopliilic attack, giving compounds of thc A-series with a C-homo-conopharynginc: skelcton (tluc to attack at c(l8) and conqwuntls ot thc B-scries with a spiro-centre (due to attack at cnrlun(5)) (.S'cheme 3). ' LXe structures of theso compounds were elucidatcd using D-incorporation uxperimcnts, 'Hand fiC-NMH. and mass spcctra. On hcating to 230°, acetylated spiroalcohol 22 was ctmvertcd, probably via the ion pair 23, into the basc 16. which on catalytic rcduction gave 13, a mambcr of thc A-series.Thc reactions mentioned above constitute interesting skelctal isomerisations of the conopharyngine skeleton. Die Indolalkaloide Voacangin(1) und Conopharyngin (2) (vgl. 121) lassen sich leicht mit Lithiumalurniniurnhydrid in Voacanginvl (3) [3J bzw. Conopharynginol (4) und anschliessend in die entsprechendcn Tosylatc 5 bzw. 6 141 uberfilhren. Die kri-153. Mitt, s. [l].

Aromatic chemical shifts in ar‐hydroxy‐ and ‐methoxy‐substituted indole alkaloids; reference data and substituent‐induced chemical shifts for ten different chromophoric groups

“…By far the largest group of alkaloids studied is that having an indole chromophore, but this group includes alkaloids with very diverse structures. It was at first thought that these various structural types would need to be considered separately but, since calculation showed that the SCS values for the different types were similar, the compounds have been dealt with as one group, consisting of the following types 12,23,29,79,98,112 two indole c h r o r n o p h~r e s ;~~~~~~~~.~~ various dimers, one half of which has an indole moiand miscellaneous alkaloids with an indole chromophore not belonging to the preceding…”