this group of compounds The nomenclature used by various Essay

this group of compounds. The nomenclature used by various investigators in discussing the structures of phenylpropanoids

is unwieldy.

Phenylpropanoids can conveniently be treated as a large class of natural compounds consisting of the following

groups:

1. Simple phenylpropanoids:

a) cinnamyl alcohols and their derivatives (ethers, glycosides);

b) cinnamic acids and their derivatives (esters, glycosides, other derivatives);

c) cinnamamides;

d) cinnamaldehydes;

e) phenylpropanes.

2. Complex phenylpropanoids:

a) phenylpropanoid glycosides based on phenylethanes;

b) oxidative coupling products (lignoids): flavolignans; xanthonolignans; coumarinolignans; alkaloidolignans;

neolignans; lignans (dimers and oligomers of phenylpropanoids).

3. Biogenetically related phenylpropanoids (flavonoids, coumarins, etc.).

The classification of phenylpropanoids proposed by us is based on current impressions of the biosynthesis of phenolic

compounds, in which cinnamyl alcohols 1-4 and cinnamic acids 5-10 play key roles. The literature on the distribution in plants

of the most important phenylpropanoids (groups 1 and 2) is presented according to this classification. Flavonoids and

coumarins, the biogenetic precursors of which are phenylpropanoids, can be usefully reviewed according to an overall

classification only from the viewpoint of biosynthesis.

These compounds have been described in detail as independent classes

of natural compounds in monographs and reviews [38].

Compounds 1, 5, 8, 33, and 42 provide an example of the usefulness of using a conventional numbering for the

phenylpropanoid carbon atoms that enables the propane fragment in the molecule (C-7, C-8, and C-9) to be clearly identified.

For example, these correspond to the frequently used notation (C-a, C-?, and C-?). This reveals structural features of the various

groups in phenylpropanoids. In our opinion, this approach is especially critical for interpreting and comparing spectral data

during structural analyses using 1

H and 13C NMR spectroscopy and other methods.

2. DISTRIBUTION OF PHENYLPROPANOIDS IN PLANTS

The literature on the distribution in plants of the most important phenylpropanoids indicates that plants of the families

composites or asters (Asteraceae), orpines (Crassulaceae), aralias (Araliaceae), figworts (Scrophulariaceae), willows

(Salicaceae), plantains (Plantaginaceae), mezereums (Thymelaeaceae), mints (Lamiaceae), and olives (Oleaceae) are rich sources

of BAC.

This section examines in detail phenylpropanoids of original structure that are of greatest interest for structural stud