Artemisyl skeleton

Important variants of procedure have been tested, providing wider possibilities for thio-Claisen rearrangements in synthesis like any other method for forming carbon-carbon bonds whose scope exceeds its limitations, there is the likelihood of studies of the type described in this Section being taken up in many more laboratories. Lithiation of allyl sulphides is followed by rearrangement, providing a very efficient method for the synthesis of thiols, alkyl sulphides, and hydrocarbons of the squalene type, or based upon the artemisyl skeleton. Typically, benzyl yy-dimethylallyl sulphide (65) gives (66) with four equivalents of... 

Thomas, A. F., and W. Pawlak The Synthesis and Reactions of Yomogi Alcohol. Conversion of the Artemisyl Skeleton to the Santolinyl Skeleton by a 1,2-Shift of a Vinyl Group. Synthesis of Santolinatriene. Helv. Chim. Acta 54, 1822 (1971). 

The suggestion of an alternative non-mevalonoid route in monoterpenoid biosynthesis77 has received some support in the efficient incorporation of L-[l/- 4C]valine into the DMAPP moiety of linalool 78 a pathway via deamination to dimethylacrylic acid is proposed. L-Leucine and l-valine are also incorporated, at least in part, into the DMAPP moiety of geraniol (8) and citronellol.79 (lf ,3/ )-Chrysanthemic acid (25) is biosynthesized80 in Chrysanthemum cinerariaefolium from ( R,3R) chrysanthemyl alcohol (26) but not from precursors with the lavandulyl (27) or artemisyl (28) skeletons (Scheme 4) (li ,3R)-chrysanthemyl alcohol (26) has been... 

Thermal [2,3] sigmatropic rearrangement of the sulphonium ylide (114) gives a 54% yield of a mixture of four isomeric products, the major (70%) of which is the allenic thioether (115), a species which contains the entire artemisyl carbon skeleton hydrolysis with mercuric chloride then leads to artemisia ketone in 80% yield. The second route involves methallylation of the methyl thioacetal monoxide (116), the unstable intermediate (117) on distillation being transformed into the trienic sulphide (118). The latter species on hydrolysis gives artemisia ketone in 57% yield. 

A number of monoterpenes do not fit the isoprene mle and are called irregular monoterpenes. There are three major stmctural types of irregular monoterpenes the chrysan-themyl (89), artemisyl (90), and santolinyl (91) skeletons (Charlwood and Banthorpe, 1978 Charlwood and Chari-wood, 1991a). These compounds are found primarily in the Asteraceae (they are especially well known from the genus Artemisia), although a few are found in the Apiaceae and Lamiaceae (Poulter, 1990). As two skeletal types often occur in the same plant, it is reasonable to suspect that a common biosynthetic pathway exists and it is possible that the three types arise from a common cationic species (Fig. 19.21). 

Naturally occurring monoterpenes having a carbon skeleton other than head-to-tail, e. g. derivatives of the santolinyl, artemisyl and lavandulyl type, have formally been considered to be fission products of natural /m -chrysanthemic acid 28, 143). Compounds of the first two... 

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