Derived from Cinnamic Acids

The enzyme phenylalanine ammonia-lyase (PAL) catalyses non-oxi-dative deamination of L-phenylalanine to form /ra 5-cinnamic acid 

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Simple phenols, phenolic acids derived from benzoic acid, and phenolic acids derived from cinnamic acid have been the most commonly identified... 

The lignans comprise a class of natural products, derived from cinnamic acid derivatives, which are related biochemically to phenylalanine metabolism. 

Stilbenoids are derived from cinnamic acid and three acetate units from mal-onyl coenzym A. The first part of the biosynthesis is in common to flavonoids. The two biosynthetic routes are diverging at the point of cyclization of a styryl-3,5,7-triketoheptanoic acid. A C-acylation produces a chalcone and subsequent modifications lead to the flavonoids. An aldol condensation of the same intermediate polyketide produces a stilbene-2-carboxylic acid that is unstable and constitutes a range of structures known as stilbenoids. Figure 9C.5 shows an overview of the biosynthetic pathway (Gorham 1995). 

Nucleophilic addition of thiophenol to chiral tiglic acid-derived imides proceeds in excellent yields and diastereoselectivities (eq 59). Complete turnover of both the a- and p-centers results from the use of the (Z) rather than (E) isomer. Poor p-induction was found with the imides derived from cinnamic acid. 

Synthesis of New Photocrosslinkable Polymers Derived from Cinnamic Acid... 

Photosensitized crosslinking of polymers has been the subject of numerous publications [l - 30], concerned mainly with poly(ethylene), poly(vinyl alcohol), various vinyl copolymers, copolymers of maleic anhydride and/or phtalic anhydride with styrene and some polymers derivated from cinnamic acid. The following compounds were used as sensitizers benzophenone, 4-chloro- and 4,4-dimethylbenzophenone [l, 3-6, 8, 9l, oC -and -derivatives of anthraquinone [3, 23] acetophenone, hydroquinone, triphenylmethane and pyridine li.] chlorobenzene and no less than trichlorinated n-paraffins [6], a complex of zink chloride with o-dia-nizidine fill potassium bichromate [l2j, anthracene fl3, 14] 2,5-methoxy-4-amino-trans-stilbene [l5], benzyl ideneacetophenone fl6-l8] -thiophenylacetophenone,... 

All phenylpropanoids are derived from cinnamic acid, which is formed from phenylalanine through the action of phenylalanine ammonia-lyase (PAL), which is considered the branch point enzyme between primary (shikimate pathway) and secondary metabolism [15]. 

Products of the phenylpropanoid pathway. These compounds, commonly referred to as polyphenols, are derived from cinnamic acid and include the xanthones and flavonoids. The basic structural unit of the flavonoid family (Fig. 1) comprises two benzene rings linked through a heterocyclic pyran or pyrone ring (C ring) variations in the C ring and the extent of hydroxylation define the major classes [4]. 

The intact cell assay of PAL gave us a tool to assess the possible interference of intermediates of phenyl-propanoid metabolism with PAL-activities in the tissue. It should be emphasized that in the experiments the inhibition of an enzyme already present is measured as opposed to an effect on the enzyme-content of the tissue. As Table 4 shows, derivatives of cinnamic acid, which are known to inhibit PAL in vitro (Eef. 4) also inhibit the intracellular PAL-activity. 7/hether feedback inhibition of PAL by cinnamic acid derivatives has a physiological significance in buckwheat is, however, questionable, as free derivatives from cinnamic acid do not accumulate in the tissue and may thus not be available in sufficiently high concentrations to cause inhibition of PAL. 

Inhibition of PAL-activity in vivo should result in the reduced accumulation of metabolites derived from cinnamic acid. Light-induced anthocyanin formation was used as an indicator of the in vivo production of cinnamic acid, as the anthocyanin content of a tissue can be determined by rapid and simple procedures. All compounds tested reduced the production of anthooyanins in isolated hypocotyls incubated in the light, but in these experiments a-NAA showed a nearly tenfold higher inhibitory activity as compared with B-KAA. This result clearly indicates that the action of auxins on anthocyanins exists, but is not very specific. 

This points to a regulatory function of PAL in the flow of carbon from phenylalanine to phenolics derived from cinnamic acid. However, in a recent review article Margna (2) has advanced arguments that phenol accumulation in plant cells is controlled at the level of substrate (phenylalanine) supply. 

A family of hydroxybenzoic acids (Ce-Ci) and structurally related compounds in plants is derived from cinnamic acid and p-coumaric acid. These are sometimes similar in struc-... 

Although many different compounds have been suggested as MALDI matrices, the analysis of lipids with their low molecular weights requires certain special properties of the matrix. For example, it is important that the yields of matrix (or matrix cluster) ions generated by laser irradiation are as low as possible. This is the reason why compounds that undergo photoreactions (especially matrices derived from cinnamic acid such as sinapinic add) should not be used, in order to avoid saturation of the detector by matrix-derived ions. 

Benzoic acids and benzyl alcohols (D 22.2.5) Diketides derived from cinnamic acids (D 22.3.1) Triketides derived from cinnamic acids (D 22.3.2) Stilbenes and flavonoids (D 22.3.3)... 

D 22.3 Secondary Products Derived from Cinnamic Acids and Malonate... 

Phenylpropenes are derived from cinnamic acid and share the first steps of lignin/lignan biosynthesis. Shortening of the cinnamic acid side chain by two carbons leads to compounds with a C -C skeleton called benzenoids. Other volatile... 

Typical polyketides related to lignans and flavonoids are styrylpyrones derived from cinnamic acids (the corresponding acyl-CoAs). An example of styrylpyrones is (2R,T )-4-methoxy-2-(2 -phenyleth-l -en-T-yl)-2,3-dihydropyran-6-one, better known... 

Hexacatenar compounds derived from cinnamic acid exist as dimeric molecules (Table 41) [213]. The compounds represent the seldom occurring biaxial nematic phase. Some compounds with four rings in the core are also nematic however, their biaxiality has not been proven [213],... 

Phenol carboxylic acids can also be supplied by the acetate-malonate pathway, at least in microorganisms. In higher plants, however, they are more likely to be derived from cinnamic acids. Let us consider as an example the conversion of /7-coumaric acid into /7-hydroxybenzoic acid and, subsequently, hydroquinone, a sequence of reactions discovered by Zenk. 

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