Acyclic diterpenes

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... 

The ability to synthesize diterpenes is universal to plants, since phytol, the acyclic parent compound of the series, is present in ester attachment in the chlorophyll molecule and hence occurs in all green plants. Gibberellic acid is also widespread in the plant kingdom as a growth hormone. Besides phytol and gibberellic acid, the remaining diterpenoids are very restricted in occurrence and usually occur within one or only a few plant... 

Diterpene isothiocyanates fall into three distinct structural categories regarding their carbon skeletons the acyclic tetraenes (220 and 221), the biflorane framework (including the kalihinol family) (222-238), and the amphilectane framework (including the cyclo- and isocycloamphilectanes) (239-241). Like the sesquiterpene isothiocyanates, most of these compounds were isolated along with the corresponding isocyanate and formamide compounds. 

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. 

Several additional examples of the intramolecular cycloaddition of unactivated acetylenes with isomiinchnones were reported by Maier [30]. This cycloaddition approach represents an efficient method for providing rapid access to annulated furans present in several sesqui- and diterpenes, such as the panicu-lides [51],furanonaphthoquinones [52],furodysin,andfurodysinin [53,54].The decomposition of acyclic acetylenic diazoimides 102 and 103 with Rh2(OAc)4 resulted in cycloaddition and retro-Diels-Alder extrusion of methyl isocyanate to give annulated furans 104 and 105 in good yield. The overall transformation is closely related to the intramolecular Diels-Alder reactions of acetylenic oxa-zoles extensively studied by Jacobi and coworkers [55]. 

Thus, for example, the cyclic propargylic allylic ether (242 equation 49) rearranges completely within 30 min upon treatment with Bu"Li in THF-hexane at -20 C, whereas the acyclic analog (244 equation SO) requires 12 h under comparable conditions. Alcohol (243) serves as a useful intermediate for the synthesis of cembranoid diterpenes. ... 

The synthesis of tricyclic compounds based on the cyclisation of methyl geranyl-geranoate was described eighteen years ago. However, the discovery of expoxy-squalene as an intermediate in steroid biosynthesis, and the corresponding in vitro cyclisation experiments, have re-awoken interest in this area of diterpene synthesis. The structural and stereochemical course of the in vitro cyclisation of the epoxy-trans-olefin (138) has been studied. Two A/B-trans-fused tricyclic compounds (139) and (140) have been isolated. The levantenolides (142) and (143) have been obtained by two closely related routes. In the first, the butenolide (141), derived from monocyclofamesyl bromide, afforded the a- and P levantenolides (142) and (143) on cyclisation with stannic chloride. In the second, the corresponding acyclic butenolide derived from famesyl bromide was cyclised. 

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. 

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