Lysergic acid 2-butyl amide

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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 It is a structural isomer of LSD, with the two ethyl groups on the amide nitrogen having been replaced by a single sec-butyl group, joined at the 2-position.^[3] It is one of the few lysergamide derivatives to exceed the potency of LSD in animal drug discrimination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-HT_1A and 5-HT_2A 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-HT_1A and 5-HT_2A mediated components, and while lysergic acid 2-butyl amide is more potent than LSD as a 5-HT_1A agonist, it is slightly less potent as a 5-HT_2A 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-HT_2A 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).

See also

• Lysergic acid 3-pentyl amide
• Methylisopropyllysergamide

References