Cinnamate cinnamic side chain molecules

Linear photo-polymerization (LPP) leads to a preferred depletion of the cinnamic side-chain molecules along due to the (2 -i- 2) cycloaddition reaction. 

Simple phenolic compounds include (1) the phenylpropanoids, trans-cinnamic acid, p-coumaric acid and their derivatives (2) the phenylpropanoid lactones called coumarins (Fig. 3.4) and (3) benzoic acid derivatives in which two carbons have been cleaved from the three carbon side chain (Fig. 3.2). More complex molecules are elaborated by additions to these basic carbon skeletons. For example, the addition of quinic acid to caffeic acid produces chlorogenic acid, which accumulates in cut lettuce and contributes to tissue browning (Fig. 3.5). 

Higher still up the series are amyl cinnamic alcohol and aldehyde. These are comparatively large molecules containing 14 carbon atoms, and their odors are therefore relatively similar in type, although there is still a very considerable difference in strength. Here the characteristic aldehydic note is almost missing from the aldehyde, though this may be due partly to the protective influence of the side chain. 

In hexyl cinnamic aldehyde, which has one more carbon atom in the side chain, the aldehydic note is virtually missing altogether. (The molecule is also chemically more stable.)... 

In the cinnamic molecule there is an additional conjugational effect between the double bond in the side chain and the unsaturated benzene ring. The saturated form, phenylpropyl alcohol is again the harsher of the two in character. 

Flavonoids serve as flower pigments, UV protectants, phytoalexins and signal molecules (1,2). Unlike BPS, CHS exhibits a broad substrate specificity (Table I). H. androsaemum CHS and the enzymes from other sources (27) accepted CoA-linked benzoic acids as minor subshates and formed the respective benzophenones. An efficient but unphysiological starter unit is benzoyl-CoA for 2-pyrone synthase (2-PS) that performs only two decarboxylative condensations with malonyl-CoA to produce 6-phenyl-4-hydroxy-2-pyrone (28). In cell cultures of H. androsaemum, benzoic acid originates from cinnamic acid by side-chain degradation (29). The underlying mechanism is CoA-dependent and non-) -oxidative. The complete sequence of enzymes involved was detected. 

Lignans are C-18 natural compounds formed essentially by the union of two molecules of phenylpropene (C-6, C-3) formed from cinnamate derivatives. Lignans are optically active compounds and the union takes place between the middle carbons of the monomers side chains. Important pharmaceutical examples are the lignans of Podophyllum... 

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