Acyclic Terpenoids

This Report follows the pattern established in Volumes 1 and 2 of the series, surveying the main developments in the chemistry of acyclic terpenoids which appeared in print during 1980 and 1981. As usual, there has been a preponderance of papers dealing with the chemistry of geranyl and neryl compounds, but there has also been substantial new synthetic work on functionalised isoprenes and on isoprene telomers. Relevant reviews which were published during these years include articles on the stereochemistry of 

Reviews (in Japanese) on the synthesis of terpene derivatives from isoprene (1) and on isoprene-derived chemicals have been published. Picture grammars bounded by a finite set of rules have 

Calculated c.m.r. spectra have been obtained for some terpene 

Of the compounds formed when isoprene is reacted with diethylamine 

T/T coupling predominates, but suitable adjustment of the reaction conditions allows the H/T linalylamine (11) to become the major product. The useful selective ozonolysis of a single double bond of cyclic dimers and triraers of isoprene (1) has previously been 

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The number of nitrogen- and sulfur-containing derivatives of acyclic terpenoids that are known to be important fragrance and flavor substances is smaller than in the nonterpenoid aliphatic series discussed in Section 2.1.6. However, a few nitriles are used in rather large amounts in soap perfumes because of their relatively high stability toward alkali. 

Boron trifluoride etherate promotes the fWt/a-selcctivc oxacyclization of polyepoxides derived from various acyclic terpenoid polyalkenes, including geraniol, farnesol, and geranylgeraniol, providing an efficient and stereoselective synthesis of substituted oxepanes and fused polyoxepanes. The oxacyclization transformations may mimic ringforming steps in the biosynthesis of trans-syn-trans-fused polycyclic ether marine natural products <2002JOC2515>. 

Acyclic tritetpenes can be considered as aliphatic hydrocarbons and are a iydroxylated by a numbo of microorganisms. The microbial oxidation of a varied of acyclic terpenoid hydrocarbons has been investigated by Nakajima, and aldrough terminal alcohols can obtained, for example pristanol (39) from pristane (38 equation 11), further oxidation can also occur. 

In contrast to all of the terpenoids considered so far rubber is an all cis acyclic terpenoid. This difference is reflected in the incorporation of tritium from [2- " C,3R,4S- H]mevalonic acid but not from the (4R)-isomer. The polyprenols (118) contain both cis- and trans-double bonds. Because of their size, biosynthetic experiments are particularly suitable for determining the number of each. In most cases examined in this way, three double bonds have a trans origin [i.e. including the terminal double bond (118 n = 3)] and the remainder are cis. 

Miyazawa, M., H. Nakai, and H. Kameoka, 1996b. Biotransformation of acyclic terpenoid ( )-franj-nerolidol and geranylacetone by Glomerella cingulata.. 1. Aerie. Food Chem.. 44 1543-1547. 

Natural Acetylenic and Olefinic Compounds, excluding Marine Natural Products Acyclic Terpenoids Insect Pheromones and Related Behaviour-modifying Chemicals Olefinic Microbial Metabolites, including Macrocyclic Compounds Prostaglandins Fatty Acids and Glycerides Polar Lipids. 

The biotransformation of acyclic terpenoid hydrocarbons usually proceeds very slowly and often gives a variety of useless and difficult-to-separate metabolites. For example, when p-m3U cene 1 was oxidized by Aspergillus niger ITS 191 for 7 days, the total content of conversion products in the neutral fraction corresponded to less than 10% of the initially added substrate [1,2]. The three main conversion products were identified as diols 2-4, probably arising from the hydrolytic opening of the corresponding epoxides. 

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