{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T18:42:11Z","timestamp":1772822531741,"version":"3.50.1"},"reference-count":51,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T00:00:00Z","timestamp":1772755200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Inserting a sulfur atom into the 1,2-dithiolane ring of lipoic acid (LA racemate) is a promising approach for improving the diversity of lipoic acid (LA racemate). For this purpose, we prepared 1,2,3-trisulfur\u2013lipoic acid derivatives (trisulfur lipoic acid (R-enantiomer, TR-LA, trisulfur lipoamide, racemate TLPA)) by the reaction of R-LA (lipoic acid R-enantiomer) or lipoamide (LPA) and H2S and performed precise stereochemical studies. As a result, the 6-membered-1,2,3-trisulfur ring (TR-LA and TLPA) showed a completely different profile from that of the five-membered dithiolane compounds (R-LA and LPA) in 1H- and 13C-NMR spectroscopy. Raman spectroscopy of TR-LA and TLPA showed a different profile to that of LA and LPA, which also indicates the uniqueness of the 6-membered 1,2,3-trisulfur ring chromophore. The regeneration of lipoic acid from 1,2,3-trisulfur lipoic acid (TR-LA) was achieved using a phosphine derivative and sodium cyanide while maintaining the stereochemistry of the chirality center, with an almost quantitative yield.<\/jats:p>","DOI":"10.3390\/molecules31050883","type":"journal-article","created":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T13:00:02Z","timestamp":1772802002000},"page":"883","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Spectroscopic Studies of 6-Membered Lipoic Acid Derivative, 1,2,3-Trithiane-4-pentanoic Acid, and Its Characteristic Stereochemical Profiles"],"prefix":"10.3390","volume":"31","author":[{"given":"Seiichi","family":"Matsugo","sequence":"first","affiliation":[{"name":"Department of Applied Life Sciences, Faculty of Applied Life Sciences, Niigata University of Pharmacy and Medical and Life Sciences, Higashijima 265-1, Akiha, Niigata 956-8603, Japan"},{"name":"School of Natural System, College of Science and Engineering, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Masaru","family":"Kojima","sequence":"additional","affiliation":[{"name":"Department of Applied Life Sciences, Faculty of Applied Life Sciences, Niigata University of Pharmacy and Medical and Life Sciences, Higashijima 265-1, Akiha, Niigata 956-8603, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yutaka","family":"Nakamura","sequence":"additional","affiliation":[{"name":"Department of Applied Life Sciences, Faculty of Applied Life Sciences, Niigata University of Pharmacy and Medical and Life Sciences, Higashijima 265-1, Akiha, Niigata 956-8603, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-4794-4415","authenticated-orcid":false,"given":"Yasushi","family":"Maeda","sequence":"additional","affiliation":[{"name":"Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1, Bunkyo, Fukui 910-8507, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1126\/science.114.2952.93","article-title":"Crystalline alpha-lipoic acid; a catalytic agent associated with pyruvate dehydrogenase","volume":"114","author":"Reed","year":"1951","journal-title":"Science"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"227","DOI":"10.1016\/0891-5849(95)00017-R","article-title":"Alpha-Lipoic acid as a biological antioxidant","volume":"19","author":"Packer","year":"1995","journal-title":"Free Radic. 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