Carbon-13 NMR spectra of kauranoid diterpenes (original) (raw)
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Diterpenes from Different Fungal Sources and Their 13C-NMR Data
Terpenes and Terpenoids, 2018
Diterpenes are one of the classes of natural products with about 7000 structures. The basic skeleton of diterpene contains 20 carbon atoms. Microbes contain a large number of diterpenoid with many oxidized carbons and nitrogen atoms. To date, a number of secondary metabolites have been isolated from fungal sources, and some of these examples showed diverse structural features and interesting biological activities. These classes of compounds have attracted the interest of natural product scientist due to their potential biological activities. This chapter includes recently (2013-2018) isolated compounds from various fungal sources especially cythane, clerodanes, halimanes, abietane, and indoletype diterpenes. Biosynthetic pathway of plants and fungi diterpenes showed homology at initial steps but showed differences at latter steps. The biological activity and 13 C-NMR data of these recently isolated compounds have been discussed. These diterpenes exhibited potential nitric oxide, anticancer, antioxidant, and antitumor properties. The diterpenes are clerodane, labdane, and kaurane derivatives. A brief discussion on the 13 C-NMR chemical shifts of these diterpenes has been discussed at the end of each type.
Occurrence, Biological Activities and Synthesis of Kaurane Diterpenes and their Glycosides
Molecules, 2007
This paper presents a review on kaurane diterpenes and their glycoside derivatives, covering aspects of their occurrence, biological activities and the synthesis of these natural products and their analogues. First, it shows and classifies diterpenes, in accordance with the already established structural criteria in the literature. Then, kaurane diterpenes are presented, focusing on their chemical structures, occurrence in the plant kingdom and their main, recently described, biological activities. Moreover, the most significant works, published between 1964 and November 2006, which describe the total synthesis or structural transformations of some kaurane diterpenes, including either semisynthetic and/or microbiological methodologies, are consisely reviewed. At this point, some general considerations on glycosides are introduced, and kaurane glycosides are presented and discussed on the basis of their toxic importance and occurrence in the plant kingdom, having focused on related aspects of their biological activities and the relationships between these activities and the structural factors of their molecules. Finally, the principal methods of glycosidation by enzymatic and chemical processes are both presented, and a few papers on the synthesis of kaurane glycosides are succinctly discussed.
The Remarkable Structural Diversity Achieved in ent-Kaurane Diterpenes by Fungal Biotransformations
Molecules, 2014
The use of biotransformations in organic chemistry is widespread, with highlights of interesting applications in the functionalization of natural products containing unactivated carbons, like the kaurane diterpenes. A number of compounds with kaurane skeletons can be isolated in large amounts from several plant species and a myriad of biological activities has been related to these compounds. Studies on structure versus activity have showed that, in most cases, in kaurane diterpenes, activity increases with the increase of functionalization. Since naturally occurring kaurane diterpenes usually have limited functional groups to be used as targets for semi-synthetic modifications, production of more polar derivatives from kaurane diterpenes have been achieved mostly through the use of fungal biotransformations. In this review, selected examples the wonderful chemical diversity produced by fungi in kaurane diterpenes is presented. This diversity includes mainly hydroxylation of nearly all carbon atoms of the kaurane molecule, many of them carried out stereoselectively, as well as ring rearrangements, among other chemical modifications. Sources of starting materials, general biotransformation protocols employed,
Phytochemistry, 2009
The diterpenes ent-kaur-16-en-19-oic acid (1) and ent-beyer-15-en-19-oic acid (2) are the major constituents of a spasmolytic diterpenic mixture obtained from the roots of Viguiera hypargyrea, a Mexican medicinal plant. Microbial transformation of 1 and 2 was performed with Aspergillus niger. Two metabolites, ent-7a,11b-dihydroxy-kaur-16-en-19-oic acid (4) and ent-1b,7a-dihydroxy-kaur-16-en-19-oic acid (5), were isolated from the incubation of 1, and one metabolite, ent-1b,7a-dihydroxy-beyer-15en-19-oic acid (6), was isolated in high yield (40%) from 2. The structures were elucidated on the basis of spectroscopic analyses and confirmed by X-ray crystallographic studies. Compounds 1-4 and 6 and methyl ester derivatives 4a and 6a were evaluated for their ability to inhibit the electrically induced contraction of guinea-pig ileum. Compounds 1, 3, 4, 4a and 5 were significantly active. These results showed that dihydroxylation of 1 at 7b, 11a-, and 1a, 7b-positions resulted in a loss of potency.
Magnetic Resonance in Chemistry, 2005
The structural characterization of two new, unusual kaurene diterpenes isolated from roots of Erythroxylum barbatum is described. 1D NMR and several 2D shift-correlated NMR pulse sequences (1 H, 1 H-COSY, HMQC, HMBC and NOESY) were used for structure elucidation and the unambiguous 1 H and 13 C chemical shifts assignments. Single crystal X-ray diffraction analysis was also used to confirm the final relative configuration of the compounds possessing the C-20 methyl and the CH 2-15 methylene groups in cis-orientation.
13C NMR spectral analysis of eperuane diterpenes
Phytochemistry, 1977
Key Word hde~-'~C NMR spectra; eperuane diterpenes; methyl enf-fabdan-8B-ol-15-te; enf-labdan-8g,l5dial; ent-labd-lZen-8~-ol-l5-oic acid; eperua-7,13-dien-15-oic acid; methyl eperua-8(9)-en-15-oate. Ab@raet-The 13C NMR spectra of some eperuane diterpeaes have been recorded and the signals assigned. The sabstituent shielding effects in these compounds, in comparison with those observed in other series of diterpenes, are also presented.
13C nmr spectroscopy of tetracarbocyclic diterpenes and related substances
Tetrahedron, 1981
Ab&act-A carbon shift analysis of hibent, phyllocladene, isophyllocladene, cafestol. cafamarine. mascaroside and h~bane-like substances is presented. Structure analysesz2 and partial syntheses" of tetracarbocyclic diterpenes of the hibaene,' phyllocladene and kaurene' types have led to the accumulation of a number of structurally similar substances, whose close relationship made them good substrates for "C NMR analysis and hence for the acquisition of physical data of importance for future research in diterpene chemistry. Compounds l-5 represent materials of mainly hibaene
13C NMR spectroscopy of oleanane triterpenoids
Progress in Nuclear Magnetic Resonance Spectroscopy, 1992
13(18) 13(18) 12 12 12 12 12 12 12 Methyl serjanate Methylacetyl serjanate Methyl-3-keto-serjanate Asterogenic acid methyl ester Acutangulic acid diacetate Arjunic acid Polyalaeic acid Arijunolic acid Methylarijunolate Methyl arijunolate triacetate Medicagenic acid Bayogenin triacetate See structure (Appendix A) COOMe 12 CHzOH COOMe CH2OH CHO CH2OH CH2OH 12 CH2OH 12 CH2OH 12 CH2OAc 12 COOH CH2OH 12 CH2OH COOMe COOMe 12 COOMe COOH COOH COOMe COOMe 9(11),13(18) COOH 12 CH2OH CH2OH 12 COOMe 9(11),13(18) CH2OH COOH 12 COOMe 12 COOH 12 COOH 12 COOMe 12 12 COOMe COOH 12 COOH 12 CH2OH CH2OAc CH2OH CH2OH