Acyclic diterpene

Acyclic diterpene-a-lactones Salix matsudan SiOj Hx + McjCO Hx + CHCI3 + UV Isolation 57 fD 0... 

Phytol, a diterpene alcohol (3,7,11,15-tetramethyl-2-hexadecen-l-ol), occurs in two isomeric forms fraus-phytol 110 and czs-phytol 111 (Structure 4.33). Phytol was first isolated at the beginning of the nineteenth century during esterification of the chlorophyll molecule. It is a constituent of nettle and many essential oils. Another acyclic diterpene, geranylcitronellol 112, also occurs in essential oils. 

While there are a number of acyclic diterpenes such as phytol, cyclization of these acyclic diterpenes, driven by various enzymes, leads to the formation of cyclic diterpenes. A number of other biogenetic reactions, e.g. oxidation, also bring in variation among these cyclic diterpenes. 

Lycium chinense Miller Di Gu Pi (Matrimony vine) (root bark) Cinnamic acid, betaine, peptides, acyclic diterpene glycosides, polysaccharide, kukoamines.33 Lower blood sugar and blood pressure, antipyretic, stimulate uterine contraction, antibacterial. 

Acyclic diterpene glycosides Acyl flavonol di-gycoside Adenine... 

Two acyclic diterpene tetraene isothiocyanates have been isolated from sponges so far. Famesyl isothiocyanate (220) was obtained from Pseudaxinyssa pitys [184] while compound (+)-221 was isolated from Halichondria sp. [185]. Their structures were elucidated by interpretation of their spectral data. 

Plaunotol, (2, E, El-2-(4,8-Dimerhyl-3,7-nonadte-nyl)-6-methyi-2,6-octadiene-l,8-diol (E.Z.EJ-7-hydroxymethyl-3, 11,15-trimethyl-2,6,10.14-hexadecatetraen-l -ol CS-684 Kelnac. Cj H O,. mol wt 306 49. C 78.38%, H 11.18%, O 10.44%. Acyclic diterpene alcohol isolated from a Thai medicinal plant identified as Croton sublyratus Kurz, Euphorbiaceae. Isoln, synthesis and anti-ulcer activity H. Mishima et at., Japan. Kokai 77 62,213 eidem, U.S, pat. 4,059,641 (both 1977 to Senkyo) A. Ogiso et aL, Chent... 

Crinitol, an Acyclic Diterpene Diol from Marine Algae... 

In addition to crinitol, two structurally related minor acyclic diterpene alcohols, geranylgeraniol (3) and phytol, were also isolated from the active fraction in S. tortile, although neither of them exhibited any activity up to 800 / g/ml as listed in Table 1. In addition, several derivatives of crinitol as well as its two common natural congeners, famesol... 

I. Kubo, T. Matsumoto and N. Ichikawa, Absolute configuration of crinitol, an acyclic diterpene insect growth inhibitor from the brown algae Sargassum tortile, Chem Lett., (1985) 249-252. 

R. Vails, B. Banaigs, C. Francisco, L. Codomier and A. Cave, An acyclic diterpene from the brown alga Biiiircaria bifurcata. Phytochemistry, 25 (1986), 751-752. 

G. Combaut and L. Piovetti, A novel acyclic diterpene from the brown alga BiSircaria bilurcata. Phytochemistry, 22 (1983), 1787-1789. 

L. Semmak, A. rzouf, R. Vails, B. Banaigs, G. Jeanty and C. Francisco, Acyclic diterpenes from BiAircaria biiurcata. Phytochemistry, 27 (1988), 2347-2349. 

Isoprene (2-methylbnta-l,3-diene), a branched diunsaturated Cj hydrocarbon, is the bnilding block of a large family of open-chain and cyclic isoprenoids and terpenoids (Fig. 4.8). Essential oils of higher plants are enriched in monoterpenes (Cj ) with two isoprene nnits. Farnesol, an unsaturated alcohol, is an example of a sesquiterpene with three isoprene units. The acyclic diterpene phytol is probably the most abnndant isoprenoid on Earth. It occnrs esterified to chlorophyll a and some bacteriochlorophylls and is. 

As mentioned previously, the acyclic diterpenoids and cembranoids from Eremophila species are unique in containing internal c -double bonds. The derivation of the two classes of compounds from a common precursor seems reasonable. Thus, the acyclic hydroxy diacid (95) and the all-c -cembratriene (108) must branch from the same intermediate. Nevertheless, at least one acyclic diterpene (96) contains a rroni-double bond and cyclization of its precursor would lead to cembrenes displaying a 3,4-tra/u double bond. No such examples have yet been found but a clue to their formation might be obtained from a comparison of the two cembrenoids, 107 and 109, which differ in configuration at C3 and C4. Their possible origins from acyclic precursors which differ in the geometry of the 2,3-double bond are shown in Scheme 47. 

Classification Acyclic diterpene alcohol Empirical C20H40O... 

Acyclic diterpenes are not common. Most known acyclic diterpenes are derived from hydrolysis of GGPP and relatively simple modifications (Figs. 22.3 and 22.4). The fragrant compound geranylgeraniol (3) is accumulated in the wood of Cedrela toona (Meliaceae) (Croteau and Johnson, 1985). The monounsaturated diterpene, phytol (4), is a com-... 

Fig. 22.3. Naturally occurring acyclic diterpenes (modified from West, 1981 used with permission of the copyright owner, Wiley, New York).

Several acyclic diterpenes such as geranylgeranial and geranylcitronellol (89), Fig. 22.3) have been isolated from... 

Ahlquist, L., G. Bergstrom, and C. Liuenberg, Acyclic diterpene alcohols Occurrence and synthesis of geranylcitronellol, phytol and geranylgeraniol. Prog. Chem. Fats Other Lipids, 16, 231-255 (1978). 

Baker, R., Parton, A. H. and Howse, P. E. (1982) Identification of an acyclic diterpene alcohol in the defense secretion of soldiers of Reticulitermes lucifugus. Experientia, 38, 297. 

Amico V, Oriente G, Piattelli M, Ruberto G, Tringali C (1980) A geranylacetone derivative from brown alga Cystoseria crinita. Phytochemistry 19 2759-2760 Kubo I, Smith LR (1997) Crinitol, an acyclic diterpene diol from marine algae. Stud Nat Prod Chem 20 25-39... 

Izimitani Y, Yahara S, Nohara T (1990) Novel acyclic diterpene glycosides, capsianosides A - F and I - V from Capsicum plants. Chem Pharm Bull 38 1299-1307 Jackson DM, Severson RF, Johnson AW, Herzog GA (1986) Effect of cuticular duvane diterpenes from green tobacco leaves on tobacco budwotm (Lepidoptera Noctuidae) oviposition. J Chem Ecol 12 1349-1359... 

Yahaia S, Izumitani Y, Nohara T (1988) A novel acyclic diterpene glycoside, capsianside A, from Capsicum annuum ai. fasciculatum. Tetrahedron Lett 29 1943-1946 Yahaia S, Kobayashi N, Izumitani Y, Nohara T (1991) New acyclic diterpene glycosides, capsian-osides VI, G and H from the leaves and stems of Capsicum annuum L. Chem Pharm Bull 39 3258-3260... 

The diterpenes represent a large group of terpenoids with a wide range of biological activities, and are isolated from a variety of organisms. One of the simplest and most important acyclic diterpenes is phy-tol. It is a reduced form of geranylgeraniol. This terpenoid may be the... 

Ghisalberti E L, Jefferies P R, Proudfoot G M 1981 The chemistry of Eremophila spp. XV. New acyclic diterpenes from Eremophila spp. Aust J Chem 34 1491-1499... 

Jassbi AR, Zamanizadehnajari S, Kessler D, Baldwin IT (2006) A new acyclic diterpene glycoside from Nicotiana attenuata with a mild deterrent effect on feeding Manduca sexta larvae. Z Naturforsch 61b 1138 1142... 

An important representative of diterpenoid alcohols is phytol (2 ,3,7ff,llff,15)-3,7,ll,15-tetramethylhexadec-2-en-l-ol, a constituent of chlorophylls, tocopherols and K group vitamins. Free phytol arises during chlorophyll hydrolysis by chlorophyUase as an integral part of plant catabolism in fruit ripening and yellowing of leaves. Microbial decomposition of phytol creates some unusual branched fatty acids, such as pristanic and phytanic acids (see Section 3.2.3.3.2). Acyclic diterpenic alcohol is also retinol (vitamin Aj) (see Section 5.2.1). 

GGPP is a key branch point metabolite of polyisoprenoid metabolism. Apart from the cyclic diterpenes, it is the precursor of the tetraterpenes (carotenes, xanthophylls), and acyclic diterpenes (phytol). Cyclic diterpenes compete with compounds of established importance for either GGPP or its precursors (e.g., famesyl pyrophosphate). The spotty nature of resin diterpene distribution may in part be explained by the obvious demand for carotenoids and phytyls and the relatively unestablished requirement for these nongibberellin diterpenes. 

---