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Other names | (6aR,9R)- N- (R)- 2-butyl- 7-methyl- 4,6,6a,7,8,9- hexahydroindolo- [4,3-fg] quinoline- 9-carboxamide |
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Formula | C20H25N3O |
Molar mass | 323.440 g·mol−1 |
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Lysergic acid 2-butyl amide (2-Butyllysergamide, LSB) is an analogue of LSD originally developed by Richard Pioch at Eli Lilly in the 1950s,[2] but mostly publicised through research conducted by the team led by David E. Nichols at Purdue University. It is a structural isomer of LSD, with the two ethyl groups on the amide nitrogen having been replaced by a single sec-butyl group, joined at the 2-position.[3] It is one of the few lysergamide derivatives to exceed the potency of LSD in animal drug discrimination assays, with the (R) isomer having an ED50 of 33nmol/kg for producing drug-appropriate responding, vs 48nmol/kg for LSD itself. The corresponding (R)-2-pentyl analogue has higher binding affinity for the 5-HT1A and 5-HT2A receptors, but is less potent in producing drug-appropriate responding, suggesting that the butyl compound has a higher efficacy at the receptor target.[4] The drug discrimination assay for LSD in rats involves both 5-HT1A and 5-HT2A mediated components, and while lysergic acid 2-butyl amide is more potent than LSD as a 5-HT1A agonist, it is slightly less potent as a 5-HT2A agonist, and so would probably be slightly less potent than LSD as a hallucinogen in humans. The main use for this drug has been in studies of the binding site at the 5-HT2A receptor through which LSD exerts most of its pharmacological effects,[5] with the stereoselective activity of these unsymmetric monoalkyl lysergamides foreshadowing the subsequent development of compounds such as lysergic acid 2,4-dimethylazetidide (LSZ).