DFT molecular modeling and NMR conformational analysis of a new longipinenetriolone diester

Natural sesquiterpenoids

“…186 An enantioselective total synthesis of (+)-b-himachalene has been achieved. 187 The conformations of longifolene 188 and of a longipinene derivative 189 have been studied by NMR and molecular mechanics calculations. The microbiological transformation of (+)-cycloisolongifol-5b-ol by the fungus Cunninghamella elegans has been investigated.…”

Induction of Diverse Cryptic Fungal Metabolites by Steroids and Channel Blockers

“…Based on NOESY analysis and a vicinal coupling constant of J = 3.5 Hz between H-6 and H-7, the relative configuration of sclerocyclane was assigned as 1R*, 5S*, 6R*, and 7R* (Figure 2d). [34] The absolute configuration was determined by electronic circular dichroism (ECD) data and simulation. ECD spectra were simulated for the two enantiomers [5 a (1R, 5S, 6R, and 7R) and 5 b (1S, 5R, 6S, and 7S)], and the experimental data agreed with the former (Figure S3, Tables S3, S4), thus affording sclerocyclane's complete chemical structure.…”

Structure and Conformation of a New Longipinene Diester from Stevia nepetifolia

“…Molecular modelling of longipinene 1 showed the fixed geometry of the fused four-and six-membered rings, evidenced the preferred conformation of the seven-membered ring, and showed the flexibility of the short chain ester moieties. Recently, a comparable approach was carried out for a longipinene derivative bearing the ester groups at C-7 and C-9 instead of C-7 and C-8 [14]. The wide rotameric possibilities of both (S)-α-methylbutyryl residues and inversion of the seven-membered ring generate a series of lowenergy conformers comprising 61 local minima in the relative range between 0-5 kcal mol -1 .…”

“…Mebu Mebu Ang Mebu Ang Ang H H It is relevant to remark that the cyclobutane ring exhibits a fixed geometry in which both H 4 -C 4 -C 5 -H 5 and H 5 -C 5 -C 11 -H 11 dihedral angles are close to 90° (Figure 2), thus providing very small coupling constants between H-4 and H-5 and between H-5 and H-11, but a significant long-range coupling constant ( 4 J = 6.5 Hz) between H-4 and H-11 due to a W-type coupling [14]. In addition, it is important to point out the long-range coupling constants ( 4 J = 1.5 Hz) between H-2 and H-11, due to a W-type coupling through the C-1 carbonyl group, as well as between H-2 and H-4, and between H-2 and Me-15, through the C-2, C-3 double bond ( Figure 2).…”