Erratum: Compounds Related to Saudin and Three New Series of Diterpenoids from Clutia lanceolata (Journal of Natural Products (2023) 86: 5 (1129−1149) DOI: 10.1021/acs.jnatprod.2c00761)

Sarfaraz Ahmed, Mohammad Nur-e-Alam, Ifat Parveen, Michael Threadgill, James B. Orton, Rahman M. Hafizur, Israr Khan, Mai Al-Oqail, Adnan J. Al-Rehaily

Research output: Contribution to journalComment/debatepeer-review

Abstract

Re-examination and reinterpretation of the NOESY NMR data for 11 and 12 has led to reassignment of the relative stereochemical configurations at C-5 and C-10 for both compounds. The text discussing the relative configurations for compound 11 (lanceolide K) (p 1139) should be replaced with the following: A strong NOESY cross-peak between H-5 and H3-18 established these as being cis (β-oriented) on the cyclohexane ring. Thus, the γ-lactone ring was established as being fused cis on the cyclohexane ring. A NOESY cross-peak was also observed from H-5 to H-6Pro‑R (δH 4.23) (β-oriented) but not to H-6Pro‑S (δH 4.27) (α-oriented), helping to assign the signals for these diastereotopic protons. In the δ-lactone ring, a strong NOESY interaction between H-8 and H-12 indicated that these are both cis and that the ring must be in a (flattened) conformation for this strong prow−stern interaction. Thus, the methyl at C-8 and the furan ring at C-12 must both be on the β-face (the configuration at C-12 having been assumed from earlier analogues). Strong NOESY cross-peaks were also evident from both H-8 and H-12 to H-9, so H-9 was assigned as αoriented, and the bond from C-9 to the cyclohexane must be βoriented. This single C−C bond allows rotation, and so the other NOESY interactions between the two six-membered rings would be reasonable (e.g., H3-20 to H3-17, H-8, H-9, and both H2-11; H-5 to H-8). The NOESY cross-peak from H-5 to only one H-11 proton signal (δH 1.98) shows that this proton is on the β-face of the δ-lactone. The MM2 minimized model has this proton equatorial, which is consistent with its signal having only one large coupling (Jgem = 9.9 Hz). Thus, H-11 (δH 1.89) is αoriented/axial, which was supported by its signal having three large couplings (Jgem and 2 × Jax‑ax). The text discussing the relative configurations for compound 12 (lanceolide L) (pp 1140−1141) should be replaced with the following: The configuration of 12 was assigned using MM2 minimized models of the various possible diastereoisomers, the NOESY spectrum, and 1 H−1 H coupling constants. In the cyclohexane/γ-lactone bicyclic ring, H-19 (δH 3.79) gave strong NOESY cross-peaks with H3-18 and with H-5. Accordingly, H-5, H-19Pro‑S (δH 3.79), and Me-18 were all found to be cis to each other and on the β-face. This placed H-19Pro‑R (δH 4.09) on the α-face, and a strong NOESY cross-peak to H3-20 located the latter on the α-face also. In the δ-lactone, a NOESY connection was seen between H-8 and H-12, showing that they were cis (and α-oriented); so, the furan ring and Me-17 are β-oriented. The models used suggested H-11 (δH 1.96) and H-12 as being almost eclipsed in the deformed boat conformation of the δ-lactone ring. This was consistent with the former resonating as a broad quartet with a J value appropriate for being eclipsed with H-9 and H-12. Thus, H-11 (δH 2.12) was assigned as being on the βface. NOESY interactions were observed from H-9 to H-8 and to H-11 (δH 1.96), confirming that all are on the α-face. The absolute configuration of compound 12 was assigned by analogy with those of 1 and 2. Figure 1 should be replaced to show the correct configurations of compounds 11 and 12. We are grateful to Prof. Chao Li (National institute of Biological Sciences, Beijing, China) for bringing this to our attention initially. (Figure Presented).

Original languageEnglish
Pages (from-to)2421-2422
Number of pages2
JournalJournal of Natural Products
Volume86
Issue number10
Early online date21 Sept 2023
DOIs
Publication statusPublished - 27 Oct 2023

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