Recently, lysergic acid diethylamide (LSD) analogs have appeared worldwide as designer drugs. In this study, we identified a distributed LSD analog from a paper-sheet product. Gas chromatography-mass spectrometry (GC-MS), liquid chromatography-photodiode array-mass spectrometry (LC-PDA-MS), and liquid chromatography with hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) were used to analyze the sheet product. The sheet product claimed to contain 1-(1,2-dimethylcyclobutanoyl)-N,N-diethyllysergamide (1D-LSD). However, an unknown compound was detected in the product together with tryptamine and L-tryptophan methyl ester. This compound was isolated from the sheets and identified as 1-(thiophene-2-carbonyl)-N,N-diethyl-6-methyl-9,10-didehydroergoline-8beta-carboxamide (1-thiophenoyl LSD; 1-(2-thienoyl)-LSD, 1T-LSD), using (1)H, (13)C nuclear magnetic resonance (NMR) spectroscopy and various two-dimensional NMR techniques. 1T-LSD was shown to have the thiophene-2-carbonyl group at the N(1) position instead of the 1,2-dimethylcyclobutane-carbonyl group as claimed. The amount of 1T-LSD (free base) in three individual unit from one sheet was determined to be 87-100 mug per unit using a proton-specific quantitative NMR ((1)H-qNMR) method. Deacylation of 1T-LSD to LSD was also observed to occur in methanol-d(4) during NMR analysis. The UV spectrum of 1T-LSD differed from that of other LSD analogs, and the fluorescence sensitivity was much lower. Because of concerns about the future distribution of products containing new LSD analogs, continued monitoring of newly detected compounds in sheet products is encouraged. CI - (c) 2023 John Wiley & Sons Ltd.