Lysergic acid 2-butylamide

Lysergic acid 2-butylamide (LSB or LASBA), also known as 2-butyllysergamide, 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 It is a structural isomer of LSD, with the two ethyl groups on the amide nitrogen having been replaced by a single sec-butyl group, joined at the 2-position.^[3]

Other namesLysergic acid sec-butyl amide; N-(Butan-2-yl)lysergamide; N-sec-Butyllysergamide; NSB-LA; LASBA; (8β)-6-Methyl-N-[(1R)-1-methylpropyl]-9,10-didehydroergoline-8-carboxamide

Drug classSerotonin receptor modulator; 5-HT_2A receptor agonist

Legal status

• DE: NpSG (Industrial and scientific use only)
• UK: Under Psychoactive Substances Act
• US: Schedule I (isomer of LSD)
• Illegal in France^[1]

CAS Number

• 137765-82-3 ^Y (R,R) isomer, freebase
  137765-83-4 (R,R) isomer, maleate salt

Quick facts Clinical data, Other names ...

LSB

Clinical data
Other names	Lysergic acid sec-butyl amide; N-(Butan-2-yl)lysergamide; N-sec-Butyllysergamide; NSB-LA; LASBA; (8β)-6-Methyl-N-[(1R)-1-methylpropyl]-9,10-didehydroergoline-8-carboxamide
Drug class	Serotonin receptor modulator; 5-HT2A receptor agonist
Legal status
Legal status	DE: NpSG (Industrial and scientific use only) UK: Under Psychoactive Substances Act US: Schedule I (isomer of LSD) Illegal in France[1]
Identifiers
IUPAC name (6aR,9R)-N-butan-2-yl-7-methyl-6,6a,8,9-tetrahydro-4H-indolo[4,3-fg]quinoline-9-carboxamide
CAS Number	137765-82-3 Y (R,R) isomer, freebase 137765-83-4 (R,R) isomer, maleate salt
PubChem CID	15119692
ChemSpider	23157987 N
UNII	RK6W726WK8
CompTox Dashboard (EPA)	DTXSID60929889
Chemical and physical data
Formula	C20H25N3O
Molar mass	323.440 g·mol−1
3D model (JSmol)	Interactive image
SMILES CN1C[C@@H](C(N[C@H](C)CC)=O)C=C2C1CC3=CNC4=C3C2=CC=C4
InChI InChI=1S/C20H25N3O/c1-4-12(2)22-20(24)14-8-16-15-6-5-7-17-19(15)13(10-21-17)9-18(16)23(3)11-14/h5-8,10,12,14,18,21H,4,9,11H2,1-3H3,(H,22,24)/t12-,14-,18-/m1/s1 N Key:NYFSQPDQLFFBRA-RVZJWNSFSA-N N
NY (what is this?)  (verify)

Close

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 LSB 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).