Analytical and behavioral characterization of 1-hexanoyl-LSD (1H-LSD).

The development of lysergic acid diethylamide (LSD) derivatives and analogs continues to inform the design of novel receptor probes and potentially new medicines. On the other hand, a number of newly developed LSD derivatives have also emerged as recreational drugs, leading to reports of their detection in some countries. One position in the ergoline scaffold of LSD that is frequently targeted is the N1-position; numerous N1-alkylcarbonyl LSD derivatives have been reported where the acyl chain is attached to the indole nitrogen, for example, in the form of linear n-alkane substituents, which represent higher homologs of the prototypical 1-acetyl-N,N-diethyllysergamide (1A-LSD, ALD-52). In this study, 1-hexanoyl-LSD (1H-LSD, SYN-L-027), a novel N1-acyl LSD derivative, was characterized analytically using standard techniques, followed by evaluation of its in vivo behavioral effects using the mouse head-twitch response (HTR) assay in C57BL/6J mice. 1H-LSD induced the HTR, with a median effective dose (ED50) of 192.4 µg/kg (equivalent to 387 nmol/kg), making it roughly equipotent to ALD-52 when tested previously under similar conditions. Similar to other N1-acylated analogs, 1H-LSD is anticipated to by hydrolyzed to LSD in vivo and acts as a prodrug. It is currently unknown whether 1H-LSD has appeared as on the research chemical market or is being used recreationally.

Analytical and behavioral characterization of 1-dodecanoyl-LSD (1DD-LSD).

1-Acetyl-N,N-diethyllysergamide (1A-LSD, ALD-52) was first synthesized in the 1950s and found to produce psychedelic effects similar to those of LSD. Evidence suggests that ALD-52 serves as a prodrug in vivo and hydrolysis to LSD is likely responsible for its activity. Extension of the N1-alkylcarbonyl chain gives rise to novel lysergamides, which spurred further investigations into their structure-activity relationships. At the same time, ALD-52 and numerous homologues have emerged as recreational drugs ("research chemicals") that are available from online vendors. In the present study, 1-dodecanoyl-LSD (1DD-LSD), a novel N1-acylated LSD derivative, was subjected to analytical characterization and was also tested in the mouse head-twitch response (HTR) assay to assess whether it produces LSD-like effects in vivo. When tested in C57BL/6J mice, 1DD-LSD induced the HTR with a median effective dose (ED50) of 2.17 mg/kg, which was equivalent to 3.60 µmol/kg. Under similar experimental conditions, LSD has 27-fold higher potency than 1DD-LSD in the HTR assay. Previous work has shown that other homologues such as ALD-52 and 1-propanoyl-LSD also have considerably higher potency than 1DD-LSD in mice, which suggests that hydrolysis of the 1-dodecanoyl moiety may be comparatively less efficient in vivo. Further investigations are warranted to determine whether the increased lipophilicity of 1DD-LSD causes it to be sequestered in fat, thereby reducing its exposure to enzymatic hydrolysis in plasma and tissues. Further clinical studies are also required to assess its activity in humans and to test the prediction that it could potentially serve as a long-acting prodrug for LSD.