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Phytol, an oxygenated acyclic diterpene, is an important building block of the chlorophyll molecule, from which it is obtained on treatment with alkali solution. The arrangement of isoprene units in phytol is identical with that in vitamin A, a monocyclic diterpene derivative, and is typical of the head-to-tail arrangement of isoprene units found in most terpenes.
...4,000 isoprene units. The following classes are recognized: monoterpenes, C 1 0H 1 6; sesquiterpenes, C 1 5H 2 4; diterpenes, C 2 0H 3 2; triterpenes, C 3 0H 4 8; tetraterpenes, C 4 0H 6 4; and...