Ormula was determined as C13H18O4 via HRESIMS, establishing an index of hydrogen deficiency of five. The NMR data suggested structural similarity with compound 1. Nonetheless, compound 2 lacked the olefinic proton at H six.90, which was replaced by three aliphatic protons (H 1.79, 2.43, and 2.91). These data suggested a difference amongst 1 and two of a double bond, as supported by a 2 amu difference within the HRMS data. The 1H NMR data of 2 revealed the presence of 4 olefinic protons, corresponding to two trans-disubstituted olefins (H 5.52, ddq, J = 15.5, eight.0, 1.7; five.55, ddq, J = 15.5, five.two, 1.7; 5.91, dqd, J = 15.five, 6.9, 1.7; and five.99, dq, J = 15.5, 6.9, for H-1, H-1, H-2, and H-2, Dopamine β-hydroxylase Synonyms respectively), four oxymethines (H 3.48, dd, J = 12.0, 8.6; 3.84, bq, J = two.9; 4.03, ddd, J = five.two, two.9, 1.7; and four.67, dd, J = 8.6, eight.0, for H-7a, H-3, H-2, and H-7, respectively), a single methine (H two.91, ddd, J = 12.6, 12.0, three.four, for H-4a), one particular methylene (H 1.79, ddd, J = 13.2, 12.six, two.9; and 2.43, ddd, J = 13.two, three.4, 2.9, for H-4 and H-4, respectively), two equivalent methyls (H 1.77, dd, J = 6.9, 1.7, for H-3 and H-3), and a single exchangeable proton (H 1.84, for 3-OH). The 13C NMR data revealed 13 carbons, consistent with the HRMS information and indicative of 1 carbonyl (C 173.5 for C-5), four olefinic carbons (C 125.7, 126.4, 130.6, and 134.3, for C-1, C-1, C-2, and C-2, respectively), 5 methines (C 39.0, 66.3, 81.two, 82.1, and 82.four for C-4a, C-3, C-2, C-7a, and C-7, respectively), a single methylene (C 30.0 for C-4), and two methyls (C 18.1 and 18.2 for C-3 and C-3, respectively) (see Supplementary Figures S3 and S4 for the 1H and 13C NMR spectra and Table S1). The two double bonds along with the carbonyl group accounted for 3 degrees of unsaturations, leaving the remaining two accommodated by the bicyclic ring method. COSY information identified one particular spin program as H3-3/H-2/H-1/H-2/ H-3/H2-4/H-4a/H-7a/H-7/H-1/H-2/H3-3 (Figure 2a). The following crucial HMBC correlations were observed: H3-3C-1, H3-3C-1, H-2C-2, H-7C-2, H-3C-4a, H-7aC-4, H-4aC-7, and H-4aC-5 (Figure 2a). NOESY correlations from H-1 to H-7a, from H-7a to H-2, and from H-2 to H-3 and H-2 indicated that H-1, H-7a, H-2, H-3, and H-2 have been all around the similar face. Alternatively, NOESY correlations observed from H-4a to H-7 indicated that these two protons were on the same side in the molecule but Phospholipase Inhibitor MedChemExpress opposite to the prior set (Figure 2b). Comparing all of those information with those for 1 yielded the structure of 2 (Figure 1), which was ascribed the trivial name transdihydrowaol A. The absolute configuration of two was assigned through a modified Mosher’s ester method,17 establishing the configuration as 2R, 3R, 4aR, 7S, and 7aR (Figure three).18 Compound three (1.45 mg) was obtained as a colorless oil.19 The molecular formula was determined as C13H18O4 via HRESIMS, and was the same as compound 2. The NMR data (Table S1 and Figures S5 and S6) recommended structural similarity with 2. Key differences had been a coupling constant of 0.six Hz between H-4a (H two.58, ddd, J = 7.five, 2.3, 0.six) and H-7a (H four.17, dd, J = four.six, 0.six) in three vs 12 Hz in two, as well as a NOESY correlation from H-4a to H-7a in three vs H-4a to H-7 in 2 (Figure 2d). These data implied a pseudoaxial/pseudoequatorial cis orientation of H-4a/H-7a. NOESY correlations had been also observed from H-2 to H-7a and H-4a, and from H-4a to H-3, indicating that these protons have been around the very same face (FigureTetrahedron Lett. Author manuscript; available in PMC 2014 August 07.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-P.
