Table 2. Conditions for Vocamine Cleavage Using Conventional Heating in a Round-Bottom Pressure Flaskd.
| entry | acid | solvent | additive | time (h) | voacangine (%) |
|---|---|---|---|---|---|
| 1 | HCl 3 M | H2O | 5 | 30 | |
| 2 | TCA 3 M | H2O | 7 | no reaction | |
| 3 | TFA 3 M | H2O | 7 | no reaction | |
| 4 | HBr 3 M | H2O/acetic acid | 2 | decomposition | |
| 5 | HCl 3 M | dioxane | 7 | decomposition | |
| 6 | HCl 3 M | H2O | TIS (50 equiv) | 3 | 41 |
| 7 | HCl 3 M | H2O | TIS-SH (50 equiv) | 2 | 44 |
| 8 | HCl 3 M | H2O | TIS (3.0 equiv.) | 4 | 39a |
| 9 | HCl 3 M | H2O | TIS (3.0 equiv.) | 2 | 51b |
| 10 | HCl 3 M | H2O | TIS (3.0 equiv.) | 1 | 48c |
a
17% of norvoacangine and 20% of ibogaine were also obtained.
b
7% of norvoacangine.
c
8% of norvoacangine.
d
In all cases, reactions were run at 110 °C using a voacamine concentration of 0.015 M, until no more starting material was detected by TLC analysis, except entry 10 where the reaction was stopped after 1 h. All reactions were carried out using 34 mg of voacamine except entries 8, 9, and 10 where 500 mg of voacamine was used.