Isoswertisin flavones and other constituents from Peperomia obtusifolia

A phytochemical investigation of the leaves and stems of Peperomia obtusifolia (Piperaceae) yielded a new flavone C-diglycoside isoswertisin-4`-methyl-ether-2 ``alpha-L-rhamnoside (1), along with four known compounds: isoswertisin-2 ``alpha-L-rhamnoside (2), (+)-diayangambin (3), 2-episesalatin (4) and corchoionoside C (5). The structures of the two flavone C-diglycosides (1, 2) were elucidated on the basis of 1D and 2D NMR spectroscopy and MS spectrometric data. These flavones were evaluated by bioautographic assay against Cladosporium cladosporioides and C. sphaerospermum and showed weak antifungal activity.

Absolute Configuration and Selective Trypanocidal Activity of Gaudichaudianic Acid Enantiomers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Biosynthetic origins of the isoprene units of gaudichaudianic acid in Piper gaudichaudianum (Piperaceae)

The biosynthesis of (2S)-2-methyl-2-(4'-methyl-3-pentenyl)-8-(3-methyl-2-butenyl)-2H-1-benzopyran-6-carboxylic acid (gaudichaudianic acid), the major metabolite in leaves and roots of Piper gaudichaudianum Kunth (Piperaceae), has been investigated employing [1(-13) C]-D-glucose as precursor. The labelling pattern in the isolated gaudichaudianic acid was determined by quantitative 13 C NMR spectroscopy analysis and was consistent with involvement of both mevalonic acid and 2-C-methyl-D-erythritol-4-phosphate pathways in the formation of the dimethylallyl- and geranyl-derived moieties. The results confirmed that both plastidic and cytoplasmic pathways are able to provide isopentenyl diphosphate units for prenylation of p-hydroxybenzoic acid. (c) 2007 Elsevier Ltd. All rights reserved.

Biosynthetic origin of the isoprene units in chromenes of Piper aduncum (Piperaceae)

Metabolic studies involving the incorporation of [1-13C]-D- glucose into intact leaves of Piper aduncum (Piperaceae) have indicated that both the mevalonate (MVA) and the pyruvate-triose (MEP) non-mevalonate pathways are implicated in the biosynthesis of isoprene moieties present in methyl 2,2-dimethyl-2H-1-chromene-6-carboxylate (1) and methyl 2,2-dimethyl-8- (3′-methyl-2′-butenyl)-2H-1-chromene-6-carboxylate (2). The pattern of incorporation of label from [1-13C]-D-glucose into these chromenes was determined by quantitative 13C NMR spectroscopy. The results confirmed that biosynthetic compartment of 1 and 2 could either be the plastid and/ or the cytosol or, possibly, an additional compartment such as the plastid inter-membrane space. ©2007 Sociedade Brasileira de Química.

Intraspecific variability of dihydrochalcone, chromenes and benzoic acid derivatives in leaves of Piper aduncum L. (Piperaceae)

Chemical analysis carried out in leaves of 18 specimens of Piper aduncum L. (Piperaceae) occurring at Ripasa Reserve, Araraquara, SP, Brazil indicated two distinct populations when investigated over a period of 14 months (January 2000 to February 2001) and then submitted to cluster analysis. The two groups were characterized by accumulation of prenylated benzoic acids, chromenes and dihydrochalcone, respectively. A total of seven compounds were identified by HPLC analysis and compared with standards including two prenylated benzoic acid [aduncumene (1) and 3-(3′-7′-dimethyl-2′-6′-octadienyl)- 4-methoxy-benzoic acid (5)], four chromenes [methyl 2,2-dimethyl-8-(3′- methyl-2′-butenyl)-2H-1-chromene-6-carboxylate (4), methyl 2,2-dimethyl-2H-1-chromene-6-carboxylate (2b), methyl 8-hydroxy-2,2-dimethyl-2H- 1-chromene-6-carboxylate (3) and 2,2-dimethyl-2H-1-chromene-6-carboxylic acid (2a)] and one dihydrochalcone [2′,6′-dihydroxy-4′-methoxy- dihydrochalcone (6)]. © 2009 Academic Journals.

Dicroísmo circular vibracional e eletrônico na determinação da configuração absoluta de benzopiranos de Peperomia obtusifolia e Piper gaudichaudianum (Piperaceae): implicações biológicas e biossintéticas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Prospecção química e biológica do fungo endofítico Saccharicola sp. isolado de Eugenia jambolana

Pós-graduação em Química - IQ

Dinâmica metabólica em Piper gaudichaudianum: estudo das etapas de ciclização estereosseletiva do ácido gaudichaudianico

Pós-graduação em Química - IQ

Secondary metabolites isolated from Piper chimonantifolium and their antifungal activity

In this study, the CH2Cl2 extract from leaves of Piper chimonantifolium was subjected to several chromatographic separation procedures to afford one chromene (gaudichaudianic acid) as a major compound as well as two flavonoids (dihydrooroxylin and pinocembrin) and three steroids (sitosterol, sitosteryl palmitate and stigmasterol). The structures of all determined compounds were characterised by spectrometric analysis, mainly mass spectrometry and NMR, as well as their optical properties. This article describes the first phytochemical study of the leaves of P. chimonantifolium and an evaluation of the antifungal activity of its major compounds.

Synthesis of Chromanes and 4H-Chromenes: Exploring the Oxidation of 2H-Chromenes and Dihydro-1-benzoxepines by Hypervalent Iodine(III)

The reaction of various oxygen-containing benzo-fused cycloalkenes were studied with the hypervalent iodine reagent hydroxy(tosyloxy) iodo]benzene [PhI(OH)OTs, HTIB]. 2H-Chromene and 4-methyl-2H-chromene resulted in substituted 4H-chromene and cis-3,4-dialkoxy-4-methyl-3,4-dihydro-2H-chromenes, respectively. Ring contraction to chromanes and benzofurans was observed for dihydrobenzoxepines and 2,2-dimethyl-2H-chromenes, respectively.

Synthesis of Chromen[4,3-b]pyrrolidines by Intramolecular 1,3-Dipolar Cycloadditions of Azomethine Ylides: An Experimental and Computational Assessment of the Origin of Stereocontrol

Azomethine ylides, generated from imine-derived O-cinnamyl or O-crotonyl salicylaldeyde and α-amino acids, undergo intramolecular 1,3-dipolar cycloaddition, leading to chromene[4,3-b]pyrrolidines. Two reaction conditions are used: (a) microwave-assisted heating (200 W, 185 °C) of a neat mixture of reagents, and (b) conventional heating (170 °C) in PEG-400 as solvent. In both cases, a mixture of two epimers at the α-position of the nitrogen atom in the pyrrolidine nucleus was formed through the less energetic endo-approach (B/C ring fusion). In many cases, the formation of the stereoisomer bearing a trans-arrangement into the B/C ring fusion was observed in high proportions. Comprehensive computational and kinetic simulation studies are detailed. An analysis of the stability of transient 1,3-dipoles, followed by an assessment of the intramolecular pathways and kinetics are also reported.