Cyclic terpenes

Aliphatic/aromatic. Copolymerization of aliphatic monomers (terpenes, cyclic C5, and acyclic C5) with the aromatic C9 petroleum stream is used to produce... 

Oil- and resin-based paints require a solvent to disperse the paint, reduce the viscosity, and allow for easy application. The essential requirement of the paint thinner is that it not be highly volatile, that is, have a boiling point within the range of 120-175 °C. The earliest paint thinners were the terpenes, cyclic hydrocarbons (CioHig) which come from wood and can range in boiling points of 150-180 °C. 

Hydrocarbons (aliphatic, acyclic terpenes, cyclic terpenes, benzenoids),... 

Spongiidae Spongia 230 Terpenes, cyclic polyethers, macrolides, secosterols... 

The enzyme catalyzed reactions that lead to geraniol and farnesol (as their pyrophosphate esters) are mechanistically related to the acid catalyzed dimerization of alkenes discussed m Section 6 21 The reaction of an allylic pyrophosphate or a carbo cation with a source of rr electrons is a recurring theme m terpene biosynthesis and is invoked to explain the origin of more complicated structural types Consider for exam pie the formation of cyclic monoterpenes Neryl pyrophosphate formed by an enzyme catalyzed isomerization of the E double bond m geranyl pyrophosphate has the proper geometry to form a six membered ring via intramolecular attack of the double bond on the allylic pyrophosphate unit... 

Polyterpenes. Polyterpenes is one of the first classes of non-polar tack-ifiers to be developed. Terpene monomers are a by-product in the extraction of rosin from wood stumps or tree sap, and from the extraction of oils from citrus fruits. The latter is the dominant source. As such, polyterpene prices generally mirror those of citrus fruits, which fluctuate substantially from one growing season to the next. Terpenes like rosin are cyclic, see Fig. 6, which is partly responsible for their excellent solvent properties. 

The reaction of a cyclic ketone—e.g. cyclohexanone 1—with methyl vinyl ketone 2 resulting in a ring closure to yield a bicyclic a ,/3-unsaturated ketone 4, is called the Robinson annulation This reaction has found wide application in the synthesis of terpenes, and especially of steroids. Mechanistically the Robinson annulation consists of two consecutive reactions, a Michael addition followed by an Aldol reaction. Initially, upon treatment with a base, the cyclic ketone 1 is deprotonated to give an enolate, which undergoes a conjugate addition to the methyl vinyl ketone, i.e. a Michael addition, to give a 1,5-diketone 3 ... 

A considerable number of mycotoxins that show high toxicity to vertebrates and/ or invertebrates are produced by organisms associated with crop plants (Flannigan 1991). There are many known cases of human poisoning caused by such compounds. There are three broad categories of mycotoxins represented here, based on the structures of the intermediates from which these secondary metabolites are derived. They are (1) compounds derived from polyketides, (2) terpenes derived from mevalonic acid, and (3) cyclic peptides and derivatives thereof. 

Collection site Terpene class Acyclic Cyclic Reference... 

The only other functional group is the conjugated unsaturated ester. This functionality is remote from the stereocenters and the ketone functionality, and does not play a key role in most of the reported syntheses. Most of the syntheses use cyclic starting materials. Those in Schemes 13.4 and 13.5 lead back to a para-substituted aromatic ether. The syntheses in Schemes 13.7 and 13.8 begin with an accessible terpene intermediate. The syntheses in Schemes 13.10 and 13.11 start with cyclohexenone. Scheme 13.3 presents a retrosynthetic analysis leading to the key intermediates used for the syntheses in... 

Cyclic dienes of the terpene family are also very interesting. The MS of the C10H16 compounds are discussed extensively in Budzikiewicz and coworkers.7. All of them transform... 

Comparative catalytic activities (turnover numbers and selectivity (in parentheses)) of ordered Ti-MCM-41 (A) and amorphous titania-silica (B-E) catalysts in the epoxidation of unsaturated cyclic terpenes (1-6) using anhydrous TBHP... 

Several unsaturated cyclic hydrocarbons, having the general formula C]qHj5, occur in certain fragrant natural oils that are distilled from plant materials. These hydrocarbons are called terpenes and include pinene (in turpentine) and limonene (in lemon and orange oils). 

When the diene used is cydopentadiene, endo-cyclic ring systems result such as are also produced by vegetable cells in camphor and other terpenes. 

As noted with the reactions between terpenes and dihalocarbenes, mono-insertion adducts at the more electron-rich sites can be isolated from the reaction of non-conju-gated acyclic and cyclic dienes although, depending on the reaction conditions, the bis-adducts may also be formed. Norbomadiene produces both 1,2-endo and 1,2-exo mono-insertion adducts with dichlorocarbene, as well as a 1,4-addition product (Scheme 7.4) [67]. The mono adduct produced from the reaction with dimethylvinylidene carbene rearranges thermally to yield the ring-expanded product (Scheme 7.4) [157] a similar ring-expanded product is produced with cyclo-hexylidene carbene [149]. 

Cyclic olefins and diolefins form much more aerosol than 1-alkenes that have the same number of carbon atoms (for example, cyclohexene 1-hexene, and 1,7-octadiene 1-octene). The same effect of chain length and double-bond position is observed for diolefins (1,7-octadiene > 1,6-heptadiene > 1,5-hexadiene, and 1,7-octadiene 2,6-octadiene). Heavier unsaturated cyclic compounds, such as indene and terpenes, form even more aerosol. 

Soluble in ethanol, ether (Weast, 1986), benzene, chloroform, acetone, petroleum ether, fixed oils, terpenes, and aqueous alkaline solutions (Windholz et al., 1983). Also soluble in cyclic ethers such as tetrahydrofuran. 

The cyclization of epoxyolefins has been the subject of intense study ever since the discovery that these reactions are involved in the biosynthesis of many terpenes, including cholesterol. An early example is the cyclization of geraniolene oxide 25 using BF3Et20 to give a mixture of acyclic and cyclic products (Scheme 6) [57,58]. 

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