Structure Elucidation of Xanthone Derivatives: Studies of Nuclear Magnetic Resonance Spectroscopy

Abstract

1H and 13C NMR spectra remain the first tool used by chemists to perform the structure elucidation of their products on a routine basis. It is common to provide NMR data on both proton and carbon spectra based on one-dimensional experiments, but often only proton resonances are assigned. The increasing complexity of natural compounds and their synthetic related derivatives imply the use of some more recent 1D and 2D NMR techniques. The purpose of this review is to describe the main NMR features of the most common and important classes of xanthones and also to discuss the application of several 1D and 2D NMR techniques in the structure elucidation of these compounds. A brief discussion of these NMR techniques from the point of view of structure elucidation of organic compounds will also be considered. The calculated NMR chemical shifts in the structure elucidation of xanthones and the use of NMR to study their mode of action in biological activities will be also described.

Digeranilasi Santon pada Ekstrak Diklorometana Kulit Batang Wadung (Garcinia tetranda Pierre)

“…Kemudian analisa lanjutan menggunakan spektra 1 H-NM R dan 13 C-NMR (Tabel 1) menunjukkan adanya sinyal singlet downfield pada pergeseran kimia proton δH 13,41 ppm (1H, s) dan pergeseran kimia karbon δC 182,36 ppm yang menegaskan keberadan gugus hidroksi yang terkhelat dengan gugus karbonil [15].…”

First report on mangiferin (C-glucosyl-xanthone) isolated from leaves of a wild coffee plant,Coffea pseudozanguebariae(Rubiaceae)

“…1 H spectrum of 1 in DMSO-d 6 showed three singlets at 7.371, 6.845 and 6.374 ppm and a complex 7-spin system between 3.0 and 5.0 ppm. Analysis of this second order system revealed coupling constants typical of a glucose moiety (see for example Silva & Pinto, 2005) : 4.594 (J = 9.9 Hz, H-1'), 4.047 (J = 9.9 and 8.4 Hz, H-2'), 3.202 (J = 8.4 and 8.6 Hz, H-3'), 3.123 (J = 8.6 and 9.2 Hz, H-4'), 3.171 (J = 9.2, 5.9 and 1.8 Hz, H-5'), 3.688 (J = 11.8 and 1.8 Hz, H-6'a) and 3.406 ppm (J = 11.8 and 5.9 Hz, H-6'b). The chemical shift of C-1' at 73.6 ppm indicated a C-C bond between the sugar and the aglycone.…”

Polyprenylated Phloroglucinols and Xanthones

“…Polyprenylated xanthones can further be divided, according to their oxidation degree, into mono-, di-, tri-, and so on, oxygenated compounds. Recently, the classification, synthesis, and biological evaluation of simple xanthones have been reviewed extensively [62][63][64][65][66][67][68][69][70][71]. In this chapter we focus on the so-called caged Garcinia xanthones (CGXs), owing to their similarities (isolation, biosynthesis) to the aforementioned polyprenylated phloroglucinols.…”