1. The synthesis takes place at low temperatures, so that any
intramolecular rearrangements are improbable.

2. The composition of the substances is controlled by the intermediary
compounds, the carboalkyloxy derivatives.

3. The synthesis permits of more definite evidence as regards the
structure of the resulting compounds.

4. The substances obtained are easily purified.

Depsides produced in this manner are by no means new, and were obtained
by Klepl by simply heating _p_-hydroxy-benzoic acid (_cf._ Introduction,
p. 4). This simple procedure, however, is not applicable to most other
hydroxybenzoic acids which are decomposed at the high temperature
necessary to induce reaction. Lowe and Schiff (_loc. cit._) have
obtained products similar to tannins, the latter investigator by
removing the elements of water from gallic acid, protocatechuic acid,
salicylic acid, _m_-hydroxybenzoic acid, cresotinic acid, phloretinic
acid, and pyrogallolcarboxylic acid. These depsides, however, are
amorphous substances, and it is hence difficult to substantiate their
homogeneity.


Carbomethoxylation of Hydroxybenzoic Acids

Amongst other compounds chlorphydroxybenzoic acid is used in the
preparation of the materials employed in the synthesis of depsides; the
free phenolic group, however, exerts a disturbing influence when