Relative Population of S-Form and F-Form Conformers of Bryonolic Acid and Its Derivatives in Equilibrium in CDCl3 Solutions.

Characterization of Chemical Constituents of <i>Luffa operculata</i>(Cucurbitaceae)

“…In addition, signals at δ C 62.36 and 175.64 indicated an oxymethylene carbon and an ester or amide carbonyl, respectively. The 1 H NMR spectrum also revealed characteristic signals for long alkyl chains (δ H 1.27 -1.33) as well as a signal at δ H 8.61 compatible with hydrogen of secondary amide (RCONHR') which, was further substantiated by its 13 C NMR (δ C 175.64) and IR (1621 and 1544 cm -1 ) spectra. In the 1 H-1 H COSY spectrum, the amide hydrogen with resonance at δ H 8.61 coupled to a methine hydrogen at δ H 5.13 (δ C 53.42) which in turn revealed coupling to a methyne carbinolic hydrogen at δ H 4.38 (δ C 77.32) and to a diastereotopic methylene group observed at δ H 4.45 and 4.53 (δ C 62.36).…”

Conformational study of 3β,16β-dihydroxyfriedelane by NMR and ab initio calculations

“…The DFT-optimized structure presented dihedral angles H16 a -C16-C15-H15 a and H16 a -C16-C15-H15 b with values of 31.0°and 143.5°, respectively. The Karplus equation [26] was applied to these dihedral angles, which presented similar coupling constant values (J 1 = J 2 * 9 Hz) with the experimental data for Ha-16 triplet.…”

Crystal Structure of Acetyl 29-Methyl-29-methylidene-D:C-friedoolean-8-en-3β-ol

“…1 Recently, Honda et al reported that the relative populations of these conformers in solution are greatly affected by the functionality at C-29, and that the principal factor which determines the population ratios is whether the functionality at C-29 is trigonal or tetrahedral. 2 Previously, Tabata and co-workers reported anti-allergic activities of 1 and related compounds, showing that these activities were also significantly affected by the C-29 functionality. 3 Honda et al, in a recent report 2 proposed that the MM2 program for molecular mechanic calculations is suitable for previewing the conformations of bryonolic acid derivatives.…”

“…Acetyl 29-methyl-29-methylidene-D:C-friedoolean-8-en-3β-ol (2), derived from bryonolic acid (D:C-friedoolean-8-en-3β-ol-29-oic acid) (1), was crystallographically analyzed. Rings A -E of 2 adopted chair, half-chair, half-chair, boat (with bow and stern at C-13 and C-16), boat (with bow and stern at C-19 and C-22) conformations, respectively.…”