2
/. Isoprenoids
origin, but also from such varied natural sources as microorganisms, insects,
and marine plants and animals.
The standard division of the terpenes according to carbon content into
mono-(Cio), sesqui-(Ci 5 ), di-(C 20 ), etc., terpenes is logical and convenient
and will be followed in this chapter. Because of our fragmentary exploration
of the marine environment to date, it is impossible to tell whether the distribution of various isoprenoids in marine organisms parallels that found on
land. A few ubiquitous monoterpenes, e.g., geraniol, α-pinene, have been
reported from algal sources. The bulk of that work was done in the 1950's
by Katayama, who later (1962) summarized it. The largest, yet still very modest,
number of terpenoids from marine sources have been sesquiterpenoids; there
have been a few diterpenoids, including some C 19 and C 21 offshoots; and a
number of rather closely related triterpenoids of unique structure have been
reported in the literature. Surprisingly, only two widely distributed triterpenoids, friedelin and taraxerol, have so far been isolated from marine
sources (Tsuda and Sakai, 1960; Santos and Doty, 1971). And last, we have
some unique representatives of the tetraterpenoid carotenoid pigments. Once
the extent of our knowledge of marine terpenoid compounds approaches that
of terrestrially derived substances it will be fruitful to compare distribution
and oxidation patterns, and to relate these findings to other aspects of evolutionary theory. In this connection, the fascinating observation {vide infra)
may be mentioned that a number of marine sesquiterpenes are optical antipodes of the corresponding terrestrial compounds.
A. Sesquiterpenoids
In a recent comprehensive review of sesquiterpenoid chemistry by Bryant
(1969) the author states that through 1964 more than 200 sesquiterpenoids,
divisible into 40 types, had been characterized. These figures—an average of
five compounds per structural type—are a good indicator of the great versatility of these compounds, which are made up of only fifteen carbon atoms.
Since the number of marine sesquiterpenoids that have been characterized
through 1971 totals fewer than 40 compounds, a division of this section by
individual structural type would be an exercise in overorganization.
Instead the presentation will be a pragmatic one. A brief discussion of
previously known compounds will be followed by an account of structures
which so far appear to be and perhaps are characteristic of the marine
environment. So far, sesquiterpenoids have been isolated from only four
marine phyla, the coelenterates (Cnidaria), the mollusks (Mollusca), the brown
algae (Phaeophyta), and the red algae (Rhodophyta). Clearly, therefore, an
attempt to assess phylogenetic significance is premature.
/. Isoprenoids
origin, but also from such varied natural sources as microorganisms, insects,
and marine plants and animals.
The standard division of the terpenes according to carbon content into
mono-(Cio), sesqui-(Ci 5 ), di-(C 20 ), etc., terpenes is logical and convenient
and will be followed in this chapter. Because of our fragmentary exploration
of the marine environment to date, it is impossible to tell whether the distribution of various isoprenoids in marine organisms parallels that found on
land. A few ubiquitous monoterpenes, e.g., geraniol, α-pinene, have been
reported from algal sources. The bulk of that work was done in the 1950's
by Katayama, who later (1962) summarized it. The largest, yet still very modest,
number of terpenoids from marine sources have been sesquiterpenoids; there
have been a few diterpenoids, including some C 19 and C 21 offshoots; and a
number of rather closely related triterpenoids of unique structure have been
reported in the literature. Surprisingly, only two widely distributed triterpenoids, friedelin and taraxerol, have so far been isolated from marine
sources (Tsuda and Sakai, 1960; Santos and Doty, 1971). And last, we have
some unique representatives of the tetraterpenoid carotenoid pigments. Once
the extent of our knowledge of marine terpenoid compounds approaches that
of terrestrially derived substances it will be fruitful to compare distribution
and oxidation patterns, and to relate these findings to other aspects of evolutionary theory. In this connection, the fascinating observation {vide infra)
may be mentioned that a number of marine sesquiterpenes are optical antipodes of the corresponding terrestrial compounds.
A. Sesquiterpenoids
In a recent comprehensive review of sesquiterpenoid chemistry by Bryant
(1969) the author states that through 1964 more than 200 sesquiterpenoids,
divisible into 40 types, had been characterized. These figures—an average of
five compounds per structural type—are a good indicator of the great versatility of these compounds, which are made up of only fifteen carbon atoms.
Since the number of marine sesquiterpenoids that have been characterized
through 1971 totals fewer than 40 compounds, a division of this section by
individual structural type would be an exercise in overorganization.
Instead the presentation will be a pragmatic one. A brief discussion of
previously known compounds will be followed by an account of structures
which so far appear to be and perhaps are characteristic of the marine
environment. So far, sesquiterpenoids have been isolated from only four
marine phyla, the coelenterates (Cnidaria), the mollusks (Mollusca), the brown
algae (Phaeophyta), and the red algae (Rhodophyta). Clearly, therefore, an
attempt to assess phylogenetic significance is premature.