Absolute Configuration of Menthene Derivatives by Vibrational Circular Dichroism

• Published in: Journal of natural products (Washington, D.C.) Vol. 79; no. 10; pp. 2570 - 2579
• Main Authors: Pardo-Novoa, Julio C., Arreaga-Gonzalez, Hector M., Gomez-Hurtado, Mario A., Rodriguez-Garcia, Gabriela, Cerda-Garcia-Rojas, Carlos M., Joseph-Nathan, Pedro, del Rio, Rosa E.
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society and American Society of Pharmacognosy 28.10.2016; Amer Chemical Soc
• Subjects: Ageratina - chemistry; Asteraceae; Chemistry, Medicinal; Circular Dichroism - methods; Life Sciences & Biomedicine; Mexico; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Pharmacology & Pharmacy; Plant Sciences; Science & Technology; Stereoisomerism; Terpenes - chemistry; ROOTS; P-MENTH-1-ENE-3,6-DIOLS; PHELLANDRENE; TERPENOIDS; CONSTITUENTS
• ISSN: 0163-3864; 1520-6025
• DOI: 10.1021/acs.jnatprod.6b00491

The aerial parts of Ageratina glabrata afforded (−)-(3S,4R,5R,6S)-3,5,6-trihydroxy-1-menthene 3-O-β-d-glucopyranoside (1) and (−)-(3S,4S,6R)-3,6-dihydroxy-1-menthene 3-O-β-d-glucopyranoside (3). Acid hydrolysis of 1 yielded (+)-(1R,4S,5R,6R)-1,5,6-trihydroxy-2-menthene (5) and (+)-(1S,4S,5R,6R)-1,5,6-trihydroxy-2-menthene (6), while hydrolysis of 3 yielded (+)-(3S,4S,6R)-3,6-dihydroxy-1-menthene (10), (+)-(1R,4S,6R)-1,6-dihydroxy-2-menthene (11), and (+)-(1S,4S,6R)-1,6-dihydroxy-2-menthene (12). The structures of the new compounds 1, 2, 5–9, and 11 were defined by 1D and 2D NMR experiments, while the absolute configurations of the series of compounds were determined by comparison of the experimental vibrational circular dichroism (VCD) spectra of the 1,6-acetonide 5-acetate derived from 6 and of the 1,6-acetonide derived from 12 with their DFT-calculated spectra. In addition, Flack and Hooft X-ray parameters of 10 permitted the same conclusion. The results further led to the absolute configuration reassignment of 10 isolated from Brickellia rosmarinifolia, Mikania saltensis, Ligularia muliensis, L. sagitta, and Lindera strychnifolia, as well as of 11 from Cacalia tangutica, as ent-11.