Structural and stereochemical studies of naturally occurring longipinene derivatives

Abstract

dissolved in dioxane (40 mL) was hydrogenated over palladiumon-barium sulfate catalyst (0.02 g) in the presence of quinoline (0.2 g). When the hydrogen absorption ceased, the catalyst was filtered off and the solvent was removed in vacuo, leaving a residue (0.081 g), which was dehydrated in xylene-tetrahydrofuran (4:1 v/v) solution with boron trifluoride etherate (0.9 mL) in the presence of hydroquinone (0.02 g) by boiling in a reflux condenser during 3.5 h. After cooling, the reaction mixture was treated with 10% aqueous sodium hydroxide (4 mL), taken in ethyl ether (150 mL), washed with water, and dried over anhydrous magnesium sulfate. Upon removal of the solvent the residue was purified by chromatography which gave 4 oil (0.052 g, 56% yield):

Structure and Conformation of a New Longipinene Diester from Stevia nepetifolia

“…Compound 4 (5.25% overall yield from the extract) was obtained from fractions 84-100. The physical and spectral data were identical to those reported [15]. (4R,5S,7S,8S,9S,10R,11R) Molecular modelling: Molecular mechanics were carried out with the Merck molecular force field calculations (MMFF94), as implemented in the Spartan'04 program (Wavefunction, Inc., Irvine, California).…”

Antifeedant and Cytotoxic Activity of Longipinane Derivatives

“…Bioactive principles require an accurate description of their three-dimensional structures to allow molecular visualization and to understand possible interactions with target biomole- cules. In previous works, longipinane derivatives 1-3 were used as relevant key compounds to elucidate the stereochemistry, conformation, and absolute configuration of these types of substances [8,9]. Thus, when the ECD of 1 and its diacetate derivative 2 were compared with that of closely related (+)-vulgarone, a good correspondence among them was found.…”

“…1), are generally found as complex mixtures of esters [6]. The relative stereochemistry of the C7, C8, and C9 acyloxy groups at the seven-membered ring was established by singlecrystal X-ray diffraction of rastevione acetate (10) [7] and by chemical transformation of rastevione (9) in compounds of type 1 and 3 [8]. The absolute configuration of this group of substances was found to be the same as (+)-longipinene and was established by comparing the electronic circular dichroism (ECD) curves of 1 and its diacetate 2 with vulgarone B [9].…”

“…Alkaline hydrolysis of a mixture of natural esters[8] gave 1 [m. p. 183-184°C (ref. [8], m. p. 183-184°C)], which after treatment with acetic anhydride in pyridine [8] gave 2 [m. p. 137-139°C (ref.…”

High performance liquid chromatography and nuclear magnetic resonance analysis of longipinene derivatives from Stevia subpubescens var. intermedia

“…Chemical studies on the large genus Steuia revealed that several functionalized longipinenes (Amaro et al, 1988;Gil et al, 1987;Joseph-Nathan et al, 1989;Roman et al, 1985) bearing keto, ester, and/or hydroxyl groups are representative substances of this taxon (Zdero et al, 1988). One of the most important groups of these compounds comprises the diesters of longipin-2-ene-7/3,9a-diol-l-one (1) (Table 1) in which the most common ester residues are angelates (Z-2-methyl-2butenoates), tiglates (E-2-methyl-2-butenoates), seneciates (3-methyl-2-butenoates), methacrylates (2methylpropenoates) and acetates (Joseph-Nathan et al, 1989).…”