Terpene derivatives

In several important cases, new synthetic strategies have been developed into new production schemes. An outstanding example of this is the production of an entire family of terpene derivatives from a-pinene (29), the major component of most turpentines, via linalool (3) (12). Many of these materials had been produced from P-pinene, a lesser component of turpentine, via pyrolysis to myrcene and further chemical processing. The newer method offers greater manufacturing dexibiUty and better economics, and is environmentally friendly in that catalytic air oxidation is used to introduce functionality. 

Rhodamine B vaseline [155] diphenyl, polyphenols [156] maleic and fu-maric acids [162] flavonoids [158] alcohols as 3,5-dinitrobenzoates [159, 160] gangliosides [161] 1-hydroxychlorden [162] carbamate pestiddes [163] para-thion and its metabolites [164] polyethylene and polypropylene glycols [165] terpene derivatives [166] menthol [167]... 

The most important group of derivatives for the amino function (Fig. 7-4) is the carbamate group, which can be formed by reactions with acids, acid chlorides or acid anhydrides. A series of chlorides as 2-chloroisovalerylchloride [1], chrysanthe-moylchloride [2] and especially chloride compounds of terpene derivatives (cam-phanic acid chloride [3], camphor-10-sulfonyl chloride [4]) are used. The a-methoxy-a-trifluoromethylphenylacetic acid or the corresponding acid chloride introduced by Mosher in the 1970s are very useful reagents for the derivatization of amines and alcohols [5]. 

Excellent diastereomeric ratios were achieved with terpene-derived auxiliaries. The pentacarbonyl[(-)-menthyloxycarbene]chromium complex 39 reacted with the sterically hindered 3,3-dimethylbut-l-yne to give tricarbonyl chromium naphthohydroquinone complex 40 in 81% de as the major diastereomer which was also characterised by X-ray analysis [41] (Scheme 25). Surprisingly, the application of other even more sterically demanding terpene auxiliaries or a variation of the alkyne did not improve the diastereomeric ratio [42]. 

Das aus (-)-Menthol hergestellte chirale Hydrid liefert in erster Linie mit zweizahnigen Substraten [fi-Amino- ketone, En-(2)-in-(4)-ole (s.S. 74)] gute optische Ausbeuten1. Als chirale vie. Diole werden Zucker-2,1 und Terpen-Derivate wie cis- und rrans-Pinandiol-(2,3)4 verwendet. Von den Zucker-Derivaten hat sich der Kom-plex mit 3-0-Benzyl-l,2-0-cyclohexyliden-a-D-glucofuranose am besten bewahrt2,5 (Vorschrift S. 74). 

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. 

Other observations on chemical variation within Zieria can be mentioned at this point. Zieria cytisoides form b occurs along the coast of New South Wales and in similar habitats in Tasmania. Five populations concern us here, two from the former area and three from the latter. Significant differences in the concentration of the mono-terpene derivative (-)-chrysanthenone [37] were observed by Southwell and Armstrong (1987). The populations on the mainland exhibited concentrations of the ketone of 15% and 18%, whereas those in Tasmania had higher amounts, that is, 42%, 49%, and 55%. The New Caledonian Z. chevalieri was shown to exhibit an unusual profile of compounds, relative to the Australian species, with 2,4,6-trimethoxystyrene [38],... 

Species of Bazzania have been shown to be a rich source of terpene derivatives. Bazzania trilobata is no exception as evidenced by the identification of no less than 44 compounds from European collections, and 29 from plants collected in North America (Warmers and Konig, 1999). The major differences between plants from the two sides... 

Fig. 5.8 Compounds 471-476, terpene derivatives from Cystoseira amentacea...

We focused our attention on Tall oil, a by-product of the paper industry, whenever this is prepared according to the KRAFT process. Said material consists of a mixture of highly unsaturated fatty acids (many of which with conjugated diene systems) and terpene derived rosin acids. The rosin acids have the molecular formula C20H30O2 and thus belong to the diterpenes (pimaric and abietic acids). Tall Oil has an iodine number equal to approximately 170 gl2/100 g. 

As oxidation also converts the original chiral terpene-derived group to an alcohol, it is not directly reusable as a chiral auxiliary. Although this is not a problem with inexpensive materials, the overall efficiency of generation of enantiomerically pure product is improved by procedures that can regenerate the original terpene. This can be done by heating the dialkylborane intermediate with acetaldehyde. The a-pinene is released and a diethoxyborane is produced.204... 

Various terpene-derived materials are important in the formulation of fragrances and flavors. One example is the tricyclic furan shown below, which is commercially used under the trademark Ambrox. The synthetic sequences below have been developed to prepare related structures. Suggest reagents for each step in these sequences. 

Juvabione is a terpene-derived ketoester that has been isolated from various plant sources. There are two stereoisomers, both of which occur naturally with R-configuration at C(4) of the cyclohexene ring and are referred to as erythro- and f/trao-juvabione. The 7(.S )-cnan(iomcr is sometimes called epijuvabione. Juvabione exhibits juvenile hormone activity in insects that is, it can modify the process of metamorphosis.18... 

Scheme 13.6 is a retrosynthetic outline of the syntheses in Schemes 13.7 to 13.9. The common feature of these syntheses is the use of terpene-derived starting materials. The use of such a starting material is suggested by the terpenoid structure of juvabione, which can be divided into isoprene units. ... 

Except for the syntheses using terpene-derived starting materials (Schemes 13.7, 13.8, and 13.9), the previous juvabione syntheses all gave racemic products. Some of the more recent juvabione syntheses are enantiospecific. The synthesis in Scheme 13.16 relied on a chiral sulfoxide that undergoes stereoselective addition to cyclohexenone to establish the correct relative and absolute configuration at C(4) and C(7). The origin of the stereoselectivity is a chelated TS that leads to the observed product.20... 

A quite detailed review of transannular cyclizations was published201 wherein their important role in biomimetic syntheses of sesquiterpenes as well as explanation of the biogenetic formation of the polycyclic natural compounds from their monocyclic precursors is discussed. The great significance of these transformations for the synthesis of natural products is also emphasized in a series of reviews which describe the cyclizations to form terpene derivatives, e.g., of the germacrane and humulene systems202-206. 

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