On terpenes. CLXXII. Constitution of sesquiterpenic valerenolic acid

Stereochemistry of valerenane sesquiterpenoids. Crystal structure of valerenolic acid

“…The identity of configurations at C-5, -8, and -9 is further confirmed by the 4H NMR spectra of 1 and 3 which exhibit signals of principal proton groupings with the same chemical shifts and coupling constants. 9 It is well known22 that carbon chemical shifts are influenced by chiral centers to such an extent that, even if such a center is removed by four bonds from the carbons considered, the shielding differences reflected in differences in chemical shifts for various configurations are significant. As these configu- rational differences are reflected more strongly on carbons than on protons, we expected that, should the configurations of chiral centers of 1 and 3 be different, the I3C NMR spectra would show considerable differences in carbon chemical shifts, while similar effects in the 4H NMR spectrum might be overlooked.…”

(-)-3β,4β-Epoxyvalerenic Acid from Valeriana officinalis

“…The chemical structures of all compounds were confirmed by 1 H-COSY, HMBC, and HMQC data. Based on these results, the previously reported 1 H and 13 C assignments [2], [3], [4] for 1 were also revised.…”

Addition of methanol to hexynedioic esters. Synthesis of cyclopentanediones and muconates

“…Treatment of 2 a with sodium methoxide in dry tetrahydrofuran gives only 4,4-dimethyl-3-methoxy-2-carbomethoxy-2-cyclopenten-l-one (5). Confirmation of the cyclic nature is provided by the hydrolysis and decarboxylation to 4,4-dimethylcyclopentane-l,3-dione (6), identical with material from base-catalyzed cyclization of ethyl ß,/3-dimethyl levulinate.…”

“…Methanol Concentrations»-' Solvent (%) " Reactions stopped after 0.5 hr. 6 Vpc determined as in Table I. ' Less than 2% 8 found in any run.…”

“…" Determined by vpc (column 2D; 180°; 200°) relative to an internal standard and are accurate to ±5%; the solvent is anhydrous methanol. 6 A multicomponent envelope which was eluted before starting material and products. ' Reactions carried beyond 12 hr showed an increase in volatile products and corresponded to an over-all decrease in reaction products.…”