Natural products limonene

In all of these approaches to juvabione, a precursor of the cyclohexene ring is the key intermediate. In Schemes 10.4 and 10.5, an aromatic ring is the precursor of the cyclohexene system, and the reduction of the aromatic system is carried out fairly late in the synthesis. Schemes 10.6 and 10.9 use an optically active natural product, limonene, as the starting material. This provides a useful simplification of stereochemistry, particularly if the product is required in optically active form. The syntheses in Schemes 10.4,10.6, and 10.10 proceed to build up the side chain, step-by-step, from the key cyclic intermediate. In the syntheses in Schemes 10.7, 10.8, and 10.9, the side chain is almost in final form when it is attached to the cyclic intermediate. 

Loss of a proton from the tertiary carbocation formed m this step gives limonene an abundant natural product found m many citrus fruits Capture of the carbocation by water gives a terpmeol also a known natural product... 

Terpene-based hydrocarbon resins are typically based on natural products such as a-pinene, P-pinene, and ti-limonene [5989-27-5] which are obtained from the wood and citms industries, respectively. These resins, which were originally the preferred tackifiers for natural mbber appHcations, possess similar properties to aHphatic petroleum resins, which were developed later. Terpene-based resins have been available since the mid-1930s and are primarily used in the adhesives industry. 

Other natural product-based resins also became widely used, such as the light colored Lewis acid oligomerized products of terpenes such as a-pinene, p-pinene, and limonene. These natural product resins are relatively expensive, however, and formulators now often use the newer, less expensive synthetic resins in present day natural rubber PSAs. These are termed the aliphatic or C-5 resins and are Lewis acid oligomerized streams of predominately C-5 unsaturated monomers like cis- and /rawi-piperylene and 2-methyl-2-butenc [37]. These resins are generally low color products with compatibility and softening points similar to the natural product resins. Representative products in the marketplace would be Escorez 1304 and Wingtack 95. In most natural rubber PSA formulations, rubber constitutes about 100 parts and the tackifier about 75-150 parts. 

Besides the synthesis of racemic dehydroiridodiol [37], some ex-chiral-pool syntheses using (S)-limonene have been described [38]. Dehydroiridodial was synthesized in the same manner [39]. Since the increasing number of cyclopentanoid natural products and their interesting biological activity has stimulated considerable interest in the synthesis of such compounds, we have used our methodology to provide a new asymmetric synthesis of dehydroiridodial, dehydroiridodiol, as well as analogues [40]. 

This collection includes data both on recently discovered and long known natural products. Although their values, properties etc can be found described in the literature, they are most widely scattered. Thus it is theoretically possible for a terpene expert to be uncertain as to where to find the NMR data for such a common substance as limonene. Consequently it appeared to be a good idea to compile the data on such common natural products as limonene, camphene or apigenine. This was a most work-intensive process, especially because many spectra had to be remeasured in order to achieve a certain standardization. 

Organic synthesis is the construction of complex organic compounds from simple starting compounds by a series of chemical reactions. The compounds synthesized in nature are called natural products. Nature provides a plethora of organic compounds and many of these possess interesting chemical and pharmaceutical properties. Examples of natural products include cholesterol (1.1), a steroid found in most body tissues limonene (1.2), a terpene found in lemon and orange oils caffeine (1.3), a purine found in tea leaves and coffee beans and morphine (1.4), an alkaloid found in opium. 

See the discussion above about International Eragrance Association (IFRA) guidelines that D-limonene is a recommended quencher in that it can decrease the sensitizing effect of cinnamic aldehyde when used at a 1 1 ratio with cinnamic aldehyde. IFRA guidelines also state that limonene and natural products containing substantial amounts of it should only be used when the level of peroxides is kept to the lowest practical level, for instance by adding antioxidants at the time of production. Such... 

Acute exposure to unleaded gasoline and a variety of light hydrocarbons present in gasoline produces a nephropathy in male rats characterized by (1) an excessive accumulation of protein (hyaline droplets) in epithelial cells of proximal tubule, (2) accumulation of casts at the corticomedullary junction, and (3) evidence of mild tubular regeneration. This nephropathy only occurs in male rats female rats and mice do not show any renal pathology. A number of chemicals present in unleaded petrol when tested alone have been shown to produce nephropathy and, in particular 2,2,4-trimethylpentane and decalin have been used as model compounds. Certain other industrial chemicals (1,4-dichlorobenzene and isophorone), natural products (o-limonene), and pharmaceuticals (levamisole) also produce this male-rat-specific nephropathy. Chronic exposure of male rats to unleaded petrol, 1,4-dichlorobenzene, isophorone, or o-limonene ultimately leads to the induction of a low incidence of renal adenomas and carcinomas. 

Thomas, A.F. and Bessiere, Y. 1989. Limonene. Natural Products Rep. 6(3) 291—309. Verzera, A., Trozzi, A., Stagno D Alcontres, I., Mondello, L., Dugo, G. and Sebastiani, E. 1998. The composition of the volatile fraction of calabrian Bergamot essential oil. Rivista Italiana Eppos. 20 17-38. 

Another new aldehyde was recently isolated from the oil of Rosa damascena (Bulgarian rose oil), and shown to be menth-l-en-9-al, a mixture of both diastereo-isomers (152) and (153) being present in the natural product. By oxidation of the hydroboration products of (+)-limonene (111) (see also ref. 109), both... 

Another application of stereoselective intramolecular hydroacylation to natural product synthesis, starting from (-t-)-limonen-lO-ol, leads to the bicyclo[3.3.0]octane skeleton and a synthesis of the key intermediate for carbacyclin71. 

A further application of stereoselective intramolecular hydroacylation in natural product synthesis starting from (—)-limonene leads to nepetalactonc, an iridoid-type pheromone72. 

Monocyclic monoterpenes, such as (+)-limonene, are abundant natural products and are a major product of the oils of citrus fruit peels. (+)-Limonene (Figure 45) is reported to be chemopreventive in rodents against spontaneous and chemically induced tumors [154,155]. 

Use Technically important M. are geraniol, a- pi-nenes, limonene, cymenoles, 3- carenes, and cam-phor. M. alcohols usually occur in esterified form, these esters are used as fragrances, flavor, and spice substances in the perfume, cosmetic, and food industries. Some enantiomerically pure M. are used in stereospecific syntheses of certain natural products. 

Often mixtures of terpene products or so-called natural products show allergic effects, e.g. fragrant mixtures containing d-limonene, tea tree oil, oilseed rape. Consumer products such as deodorants or perfumes also contain terpenes with allergic potential. ... 

Examples of allergic solvents are terpene products with high sensitivity potential, which can cause positive test reactions (patch-test) or even allergic diseases (contact sensitization and dermatitis). Allergic dermatitis can even be provoked by d-limonene in the air. Terpenes and terpenoid substances are found especially in natural products , e.g., cosmetic products, foods, and plants (oilseed rape). ... 

---