Terpenes, chemistry

The catalytic oxidation of isophorone (259—261) or P-isophorone (262,263) to ketoisophorone [1125-21 -9] (2,6,6-trimethyl-2-cyclohexen-l,4-dione) has been reported. Ketoisophorone is a building block for synthesis in terpene chemistry and for producing compounds of the vitamin A and E series. 

In contrast to the wide application that nitrosyi chloride has found in terpene chemistry, nitrosyi fluoride has only recently been discovered. Its first use in steroid chemistry was reported by Boswell who treated cholesterol acetate with nitrosyi fluoride at 0° in methylene dichloride and obtained the 5a-fluoro-6-nitrimine (31) already mentioned in section VI (page 461) in connection with the synthesis of 6,6-difluoro steroids. This... 

Except for terpene chemistry, the Wagner-Meerwein rearrangement is of limited synthetic importance. It is rather found as an undesired side-reaction with other reactions, for example in the synthesis of alkenes by elimination reactions. 

Another very common phytochemical isolated was phytol (3,7,11, 15-tetramethyl-2-hexadecen-l-ol), the diterpenoid alcohol which forms the "tail" of chlorophyll. This compound is nearly insoluble in water, but when applied as a 0.1 mM (0.003 wt. %) solution in 0.1% DMS0 it increased onion germination while decreasing germination in sorghum, wheat, and carrot. The germination effects are significant at only the 95% level, but pretreatment studies are planned as part of other terpene chemistry studies at SRRC and LSI). 

The three main platform molecules employed in terpene chemistry are a-pinene and / -pinene, which are extracted from turpentine oil (350000 t a-1) a co-product of paper pulp industry, and limonene extracted from citrus oil (30000 t a-1). 

WaUach, O. Justus Liebigs Ann. Chem. 1892, 272, 99. Otto Wallach (1847—1931), bom in Konigsberg, Prussia, studied under Wohler and Hofmann. He was the director of the Chemical Institute at Gottingen from 1889 to 1915. His book Terpene und Kampfer served as the foundation for future work in terpene chemistry. Wallach was awarded the Nobel Prize in Chemistry in 1910 for his work on alicyclic compounds. Moore, M. L. Org. React. 1948, 5, 301. (Review). 

New Applications for Bismuth(III) Salts in Organic Synthesis From Bulk Chemicals to Steroid and Terpene Chemistry... 

Wagner-Meerwein type rearrangements have also been widely reported in terpene chemistry [127, 128]. One well-known transformations involves the... 

A high variety of isoprenoids is also observed for fossil molecules (Fig. 11.1, pink ribbon, first to the left). This suggests that the first cnidarians at Cambrian times have extensively exploited what the terpene chemistry allows (Pietra 1995). Although overshadowed by diagenetic transformations, and not comprising volatiles for obvious reasons, Chart 16.1 is suggestive of the structure of these early isoprenoids. 

Interestingly, considerable geographic variation Is known to exist In the terpene chemistry of Douglas-flr (10,11). Our... 

Stepwise discriminant analysis was used to determine how tree chemical, phenologlcal, and physical parameters differed between sites (Table VII). Only seven of the 18 variables used were needed to completely differentiate the trees at the 2 sites (F/y ] 93) = 210.36 p < 0.001). The magnitudes of the standardized discriminant function coefficients for the Included variables Indicated that the differences between sites were largely due to terpene chemistry (Table VIII). The discriminant function contrasts primarily the relative concentration of alpha-plnene versus the concentration of several terpenes, particularly bornyl acetate and beta-plnene. Examination of the discriminant scores showed that the stressed trees loaded negatively on the function (x discriminant score = -2.23), while the non-stressed trees loaded positively (x discriminant score = 3.38). In other wards, trees from the stressed site were higher In alpha-plnene vdille the non-stressed trees contained more bornyl acetate, beta-plnene, and other terpenes In their young needles. 

Data from all three studies show that. In all cases, the terpene chemistry of young foliage, or qualitative defenses, was the most important factor In reducing budworm success. The protein complexlng capacity, or quantitative defenses, of this tissue was not Important In reducing budworm success In any of the studies. 

Vcrghese, J. Terpene Chemistry, Tata McGraw-Hill New Delhi, 1982 pp 137-148. 

The scope and depth of his work is reflected by the numerous awards he received, among them the Eugene H. Houdry Award in Applied Catalysis, the Chemical Pioneer Award, and the following American Chemical Society awards The Fritzsche Award for his contributions to terpene chemistry, the Petroleum Chemistry Award, and the E. V. Murphree Award in Industrial and Engineering Chemistry. 

The sesquiterpenes, diterpenes, and poly terpenes can be considered most simply from a structural point of view as products composed of multiple units of isoprene. Structures currently assigned to some of the sesquiterpenes may have to be revised as the study of terpene chemistry advances, since many of these have been based on the validity of the isoprene rule for terpene structures and exceptions to this rule are becoming known (37). 

The nomenclature system outlined in this report follows many customary terpene practices but also conforms to established nomenclature rules and practices. The resulting terpene-like names are much simpler than the strict systematic names formed according to IUPAC rules. Replacement of the currently used common terpene names by the recommended ter-pene-like pseudosystematic names will facilitate ready recognition of the terpene hydrocarbon structures and will aid in integrating terpene chemistry with the entire field of organic chemistry. Extension of the hydrocarbon rules to the naming of functional derivatives will simplify and unify nomenclature within the terpene field. 

Using methylene-triphenylphosphorane 205, in many cases carbonyl functions have been converted into exomethylene groups in cyclic terpene chemistry. This technique was used, among others in the preparation of (+)-steviol methyl ether 244), dihydro-5,6-norcaryophyllene 245), ( )-nootkatone 246 (-)-phyllodadene 247), and (+)-e-cadinene 248). In the synthesis of the latter the trans-decalin derivative 462 was formed from the cis-decalone 461 the epimerization of which proceeded via the enol form during the methylenation 248 (Scheme 80). 

The PO-activated olefmation was also used in industrial practice, outside the area of terpene chemistry. The bisolefine product 2,2 -(p-phenylenedivinylene)-dibenzo-nitrile (25) is obtained, in a smooth reaction, from o-cyanobenzyl phosphonate (23) and terephthalaldehyde (24). It is used as an optical brightener for polyester and polyamide fibers 30 under the name PalanilbrillantweiB R . 

Proposal of isoprene rule in terpene chemistry O. Wallach... 

A large number of tertiary alkyl chlorides has been methylated. Equations 77-79 are typical41,74). The simple synthesis of (i)-cuparene 252 is an application in terpene chemistry 35). 

Several years ago, we developed a contrathermodynamic isomerization of a- to 3-pinene via diethylmyrtenylborane obtained from a-pinene by metalation-transmetalation.11 Later, (+)-p-pinene of > 99 % ee was prepared by this method.22 Extending this work to other bicyclic monoterpenes, the isomerization of (+)-2-, (+)-3-carene, and (-)-a-thujene, was studied.13 Among bicyclic monoterpene olefins with an exocyclic double bond, 3(10)-carene is a rare compound reported only a few times in the long history of terpene chemistry, and its rotation is still controversial.23,24 Sabinene is isolated from the oil of savin, and no convenient synthesis of an optically active sabinene is known. 

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