O.R. Gottlieb

Methods for the structural investigation of xanthones: Part II. Location of hydroxyl groups by ultraviolet and visible spectroscopy1

Abstract Ultraviolet spectral shifts in presence of certain additives may be used to determine the hydroxylation pattern of xanthones. Thus, 3-hydroxyxanthones are characterized by an intense band around 355 nm which appears in presence of sodium hydroxide, o- and p-Dihydroxyxanthones decompose in presence of this reagent, the reaction rate depending on the position of the substituents. While the spectra of 1-and 2-hydroxyxanthones do not suffer modification in presence of sodium acetate, 3- and 4-hydroxy groups produce typical shifts which are dependent on the presence of additional oxygen functions. The spectra of 1-hydroxy-, as well as of o-dihydroxyxanthones, are affected by the addition of aluminum chloride. 1- and 4-Hydroxy groups with unsubstituted p-positions may be detected and distinguished through the visible spectrum (350–750 nm) of the reaction product of the xanthone with 2,6-dichlorobenzoquinone chloroimide (Gibbs test). Relatively acidic hydroxyls give rise to two maxima in this region. Two maxima, even if of different relative intensity, are also obtained with o- and p-dihydroxy-, as well as with o- and p-hydroxyallylxanthones.

Xanthonolignoids from Kielmeyera and Caraipa species—13C NMR spectroscopy of xanthones

Abstract Kielcorin and the cadensins A and B , isolated respectively from Kielmeyera coriacea and Caraipa densiflora (Guttiferae), were shown to be xanthonolignoids. The structure of (5S,6S)-6(or 5)-hydroxymethyl-5(or 6)-(4″-hydroxy-3″-methoxyphenyl)-2,3:3′,4′-(2′-methoxyxanthono)-1,4-dioxane was proposed for kielcorin by analysis of high resolution MS and PMR spectra. The carbon shifts of xanthone were assigned and used in the 13 C NMR spectral confirmation of the proposed structure.

Quinone and xanthone constituents of kielmeyera rupestris

Abstract The compounds 2,6-dimethoxy-1,4-benzoquinone, 2-hydroxy-1-methoxyxanthone, 3-hydroxy-1,2-dimethoxyxanthone, 4-hydroxy-2,3-dimethoxyxanthone, 4-methoxy-2,3-methylenedioxyxanthone, 5-hydroxy-1,3-dimethoxyxanthone, 1,5-dihydroxy-3-methoxyxanthone and 3-hydroxy-1,5,6-trimethoxyxanthone were isolated from Kielmeyera rupestris A.P. Duarte.

A phylogenetic correlation of the genera Dalbergia and Machaerium

Abstract A survey of the botanical and phytochemical characteristics of a number of species of Dalbergia and Machaerium has been made. This provides a phylogenetic basis for dividing these two genera into four species series: Dalbergiae pantropicales, Dalbergia brasilianae, Machaeria scleroxyla , and Machaeria villosa . The relation of these proposals to the theory of Continental Drift is considered.

The chemistry of Brazilian guttiferae—XII : Isopentenylated xanthones from Kielmeyera and Calophyllum species

Abstract Isopentenylated xanthones from Brazilian Kielmeyera and Calophyllum species include, besides the known jacareubin (Ia) and osajaxanthone (Ib), the hitherto undescribed 6-dehydroxy-jacareubin (Ic), guanandin (IIa), isoguanandin (III) and dehydrocycloguanandin (XII).

Flavonoids and coumarins from Platymiscium praecox

Abstract The wood of Platymiscium praecox Mart. (Leguminosae-Lotoideae) contains sitosterol, 4,2′,4′-trihydroxychalcone, (2R)-7-hydroxyflavanone, (±)-7,4′-dihydroxyflavanone, (2S, 3S)-3,7-dihydroxyflavanone, 3,7-dihydroxyflavone, 3,7,4′-trihydroxyflavone, 6,7-dihydroxy-4′-methoxyisoflavone and 6,7-dimethoxycoumarin. It also contains three novel compounds: 7-hydroxy-4-methoxy-5-methylcoumarin, 7-O-glucosyloxy-4-methoxy-5-methylcoumarin and 7-hydroxy-4,8-dimethoxy-5-methylcoumarin.

Xanthones from Kielmeyera speciosa

Abstract The trunk wood of Kielmeyera speciosa St. Hil. (Guttiferae) contains β-amyrin, 6-dehydroxyjacareubin (I), 2-hydroxyxanthone (IIa), 2-hydroxy-1-methoxyxanthone (IIb), 1,3,8-trihydroxy-7-methoxyxanthone (IIIa), 1,5-dihydroxy-3-methoxyxanthone (IVa), 5-hydroxy-1,3-dimethoxyxanthone (IVb), 4-hydroxy- 2,3-dimethoxyxanthone (Va), 3-hydroxy-2,4-dimethoxyxanthone (Vd), 4-hydroxy-2,3-methylenedioxyxanthone (Vb), 3-hydroxy-1,2-dimethoxyxanthone (VIa) and 2,3-dihydroxy-1-methoxyxanthone (VIb).

Isoflavonoids from Myroxylon balsamum

Abstract Myroxylon balsamum (Leguminosae-Lotoideae) trunk wood contains a series of biogenetically related flavonoids, including the novel (±) -7-hydroxy-4′-methoxyisoflavanone, (±)-7,3′-dihydroxy-4′-methoxyisoflavanone and 2-(2′,4′-dihydroxyphenyl)-5,6-dimethoxybenzofuran.

Xanthones from Tovomita macrophylla

Abstract The wood of Tovomita macrophylla (Pl. et Tr.) Walp. (Guttiferae) contains β-amyrin, sitosterol, betulinic acid and two novel compounds for which the structures of 1,3,6-trihydroxy-2,5-diprenyl-6′,6′-dimethylpyrano(2′,3′:7,8)xanthone (tovophyllin-A) and 3,6-dihydroxy-5-prenyl-6′,6′-dimethylpyrano(2′,3′:1,2)-6″,6″-dimethylpyrano(2″,3″:7,8)xanthone (tovophyllin-B) are proposed.

Xanthones from kielmeyera excelsa

Abstract 2-Hydroxyxanthone, 1,7-dihydroxyxanthone, 1-hydroxy-7-methoxyxanthone, 2-hydroxy-1-methoxyxanthone, 1,2-methylenedioxyxanthone and 2,8-dihydroxy-1-methoxyxanthone were isolated from the wood of Kielmeyera excelsa Camb.