The dithiophenes and trithiophenes reviewed in this article are part of
a large group of biogenetically related molecules found in plants of the
family Compo sitae (Asteraceae). They include compounds having a
variable number of unsaturations, particularly double bonds and triple
bonds, which occur singly or in combinations. The first report of a
naturally occurring trithiophene, ex-terthienyl in the flowers of
Tagetes erecta, appeared in 1947 (270); the first naturally occurring
dithiophene was isolated from Bidens radiata and described in 1961
(142). The book Naturally Occurring Acetylenes, by BOHLMANN et al. (29),
is a superb review of the field up to 1972. Interestingly, out of its
more than 500 pages, only two were devoted to physiological and
pharmacological aspects. BOHLMANN and ZDERO later contributed one
chapter, "Naturally Occurring Thiophenes", to a volume Thiophenes and
its Derivatives which appeared in 1985 (57). This chapter presents a
survey of such thiophenes based on biogenetic considerations, includes
an extensive analysis of the distribution of these compounds, and
discusses methods of analysis based on UV, lH-NMR, 13C-NMR, and mass
spectra. The most recent references in the chapter came from
publications appearing in 1981. In view of the information on naturally
occurring dithiophenes and trithiophenes already available from these
sources, this survey emphas- izes the occurrence, the biosynthesis, the
synthesis, the photophysical and photochemical properties, and
especially the biological properties of these molecules. II.