Iridoids simple

Icacinaceae are a moderate-sized, primarily tropical family consisting of 52 genera, many of which are monotypic, and 300 species. Additional background on taxonomic problems surrounding the family can be found in the 1991 paper by Kaplan et al. Chemical data have been used by Dahlgren (1980) to assess these relationships with related families, but the application involved simple presence or absence data (iridoids) and did not touch upon the dynamic nature of the pathways involved. 

The family Hamamelidaceae consists of 26 genera and about 100 species of shrubs or tress known to contain tannins and iridoids. The leaves are alternate, simple, and often palmately lobed. The flowers are small and appear in spikes. The fruits are woody, capsular, and scepticidal. In Western medicine, the dried leaves of Hamamelis virginiana (hamamelis, British Pharmaceutical Codex, 1963), yielding not less that 20% of alcohol (45%)-soluble extractive, have been used as astringents for the treatment of hemorrhoids. Hamamelis water (British Pharmaceutical Codex, 1969) made from the stems has been used as a cooling application to sprains and bruises and as a styptic remedy. It is also used in cosmetics and as active ingredient of eye lotions. 

Simple iridoids are volatile iridoids of which the best known is the cat-exciting nepetalactone (C5 C50L) from Nepeta cataria (catnip) (Lamiaceae). The lactone nepetalactone, the hemiacetal neomatatabiol (G51G50H), iridodiol (in the ring opened bi-aldehyde... 

The great advantage of the type of approach used by Vandewalle is that a variety of stereochemistries of different substituents around a bicyclo[2.2. l]hep-tane skeleton is accessible using different Diels-Alder reactions, making a stereospecific approach to many iridoids possible by relatively simple manipulations of the functional groups. 

Numerous synthetic applications of the inteimolecular Pauson-Khand reaction have been reported. Pauson has reported a number of very direct tqrplications of cycloadditions of ethylene in the synthesis of prostanoids and jasmone analogs (e.g. equations 15 and 16). - This is a reliable entry to 2-sub-stituted cyclopentenones. The suitability of cyclopentene and dihydrofuran as substrates has permitted the extension of this work to the preparation of still further varieties of prostaglandin analogs (e.g. equations 27 and 51). Simple 4,5-disubstituted 2-cyclopentenones are not as directly accessible, but may be prepared from the cycloaddition products of norbomadiene (equation 45). A sequence of conjugate addition followed by retro-Diels-Alder reaction affords the product (Scheme 5). Dihydrofuran cycloadditions have been used by Billington in the syntheses of the antibiotic methylenomycin B (Scheme 6), as well as cyclomethylenomycin A (synthetic precursor to the antibiotic methylenomycin A), cyclosarko-mycin (precursor to the antitumor agent sarkomycin) ° and the iridoid Jq>anese hop ether. ... 

Biosynthesis In plants the quinoline system can be formed by several different biogenetic routes (biochemical convergence). In the Cinchona alkaloids tryptophan acts as the precursor while simple quinolines, furoquinolines, and acridines originate from an-thranilic acid. The second biosynthetic parmer is often a hemiterpene (for furoquinolines) or an iridoid monoterpene (secologanin, see secoiridoids) for Cinchona alkaloids. 

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