Depside derivatives

The partial synthesis of a depside derivative occasionally provides a convenient means of structure correlation but this procedure is more commonly used in depsidone chemistry than in structural elucidation of depsides. 

In enzymatic studies with cell-free extracts from higher plants, however, no evidence has been found to date for galloyl-CoA s involvement in the biosynthesis of / -glucogallin, or its higher galloylated derivatives an eventual role in the formation of the chemically different meta-depside bonds of gallotannins has not been investigated. 

Nielsen J, Nielsen PH, Frisvad JC (1999) Fungal Depside, Guisinol, from a Marine Derived Strain of Emericella unguis. Phytochemistry 50 263... 

Of the more than 20,000 known species of lichens, only a few have been analyzed and identified as containing biologically active secondary compounds. Most of the unique secondary metabolites that are present in lichens are derived from the polyketide pathway, with a few originating from the shikimic acid and mevalonic acid pathways (Table 1.1). Previous studies have suggested that the para-depsides are precursors to mefa-depsides, depsones, diphenyl ethers, depsidones and dibenzofurans.9,12... 

Hydroxycinnamic acids possess a C6-C3 skeleton and formally belong to the group of phenylpropanoids. The different compounds present in wine are mainly derived from the hydroxycinnamic acids caffeic acid, p-coumaric acid, ferulic acid, and sinapic acid (Fig. 9C.2). These derivatives can be present in cis- and trans-configured forms, while the trans forms are more stable and therefore more prevalent. In wine HCA are present in low amounts in their free form, while the depside forms, i.e. esters of l-(-i-)-tartaric acid, are predominant. The ubiquitous chlorogenic acids, esters of HCA and quinic acid, cannot be found in wine but are replaced by the tartaric acid esters instead (Ong and Nagel 1978 Singleton et al. 1978 Somers etal. 1987). 

Deoxyschizandrin, synthesis of 1278, 1280 Deprotonation 92-105 energy of 3, 97-100 Depsides 942-944 Derivative isotherm summation 944 Derivative spectrometry 929, 984 Derivatization, pre-analysis 985-991 DesMarteau sulfonimide, as electrophilic fluorinating agent 647 Desulfurization 1079 Detoxification, of phenoUc compounds 1361-1363... 

The two main types of hydrolysable tannins may be derived respectively from gallic acid and ellagic acid (the depside of gallic acid). These are known as gallo tannins and ellagitannins. 

In the third paper [53], a new structural class of noncatechol-containing integrase inhibitors, bisaroylhydrazines, was identified by modification of hits obtained in the previously presented studies. These compounds may provide valuable avenues for the development of HIV integrase inhibitors. Finally, also natural products, i.e., lichen acids containing depsides and depsidones, and their synthetic derivatives were identified from 3D database search as novel HIV-1 integrase inhibitors with IC50 values below 50 pM [54],... 

Several strains of the fungus Aspergillus can grow on flavonols like quercetin or rutin (a 3-0-glycosylated derivative of quercetin). It was demonstrated in the 1960s that whole-cell cultures of Aspergillusflavus convert quercetin into an insoluble depside according to Equation (14). " ... 

Depsides, in which esterification to links two polyketide-derived units [such as lecanoric acid (50)] (Fig. 5.24), are quite common among lichens (Weiss and Edwards, 1980). Many of these compounds are strongly allelopathic and are responsible for the death of trees inhabited by the dense growth of lichens (Cutler, 1992). 

Phenolic acids include the benzoic acids (Cg-Ci), e.g., gallic, vanillic, syringic, protocatechuic, p-hydroxy-benzoic acid, as well as cinnamic acids (C6-C3), e.g., caffeic, p-coumaric, ferulic, sinapic acids, and their depsides and derivates, e.g., rosmarinic acid and lithos-permic acid (Fig. 1). Phenolic acids and flavonoids in plants may occur in the free form, but they are often glycosylated with various sugars, especially glucose. Phenolic acids may also be present in the esterified as well as bound forms. Free phenolic acids are found especially in herbs and spices and, very often, in compounds responsible for antioxidant activity (benzoic and cinnamic acids and some of their derivatives). The bound forms are more common for the fruits, vegetables, and other plant materials. Therefore, in some cases, it is necessary to combine the analysis of their free and bound forms. 

This view was confirmed more directly when 5-methylorcylaldehyde (XXIV) but not orcylaldehyde was converted to substituted toluquinols and gliorosein (XXV) by Gliocladium roseum, implying that the C-methyltrans-ferase concerned could not accept the aromatic orcylaldehyde (Steward and Packter, 1968). In addition, whereas acetate (Yamazaki et al., 1%5) and or-sellinic acid (Yamazaki and Shibata, 1966) were both incorporated into the depside lecanoric acid (XXVI) (derived by esterification of two molecules of orsellinic acid) in the lichen Parmelia tinctorum, orsellinic acid was not converted to the related atranorin (XXVIl) (Yamazaki and Shibata, 1966) this... 

Comparatively little is yet known concerning the biosynthesis of the various derivatives of gallic acid, such as the esters and depsides which occur in plants. 

Mass spectrometry is another useful tool for the identification and structural elucidation of lichen substances. Tlje principles of the method are given in a review by Lehmann and Schulten (1976). The mass spectra (MS) of numerous depsides, depsidones, depsones, dibenzofuranes and diphenylbutadienes have been discussed by Huneck et al. (1968a). In the same year, Letcher (1968) published the MS of some pulvinic acid derivatives. Martinez and Mestres (1972) recorded the MS of depsidones derived from norstictic acid, and Holland and... 

Wilkins (1979) studied the MS of di- and tri-oxygenated stictane triterpenoids and their trimethylsUyl derivatives. A paper by Grigsby et al. (1974) deals with the MS of derivatives of polyporic acid, and Krause (1976) investigated the MS fragmentation of depsides, depsidones, usnic acid, terpenoids, fatty acids, di- and triglycerides and carbohydrates from lichens. Some papers deal with the MS of usnic acid and derivatives Kutney et al. (1974), Huneck and Schmidt (1980), and Schmidt et al. (1981). Ruef (1990) reported on the MS of numerous lichen xanthones. 

Secondary aliphatic acids, esters and related derivates Mononuclear phenolic compounds Depsides, tridepsides and benzyl esters Depsidones and diphenyl esters Depsones... 

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