1DD-LSD, also known as 1-dodecanoyl-LSD or as SYN-L-004, is an acylated derivative of lysergic acid diethylamide (LSD). In animal studies, it produces a weak head-twitch response but with 27x lower potency than LSD itself. It is being researched as a potential slow-onset, long lasting prodrug for LSD which is expected to have reduced psychoactive effects.

Analogues of 1DD-LSD include ALD-52 (1A-LSD), 1P-LSD, 1B-LSD, 1H-LSD, and 1V-LSD, among others.