Solanesol synthesis

Solanesol and other prenyl alcohols are important as metabolites in mulberry and tobacco leaves and in the synthesis of isoprenoid quinones. Hence, Sato and collaborators107 have developed a stereoselective synthesis of all-trans-polyprenol alcohols up to C50. Construction of the requisite skeletons was accomplished by the alkylation of a p-toluenesulphonyl-stabilized carbanion, followed by reductive desulphonylation of the resulting allylic sulphonyl group. This was achieved most efficiently by the use of a large excess of lithium metal in ethylamine (equation (43)), although all reaction conditions led to mixtures. The minor product results from double bond rearrangement. 

A method has been described for the functionalization of the isopropylidene terminus of isoprenoids. For example, geranyl benzyl ether (208) was converted into the phenyl thioether (210) by treatment with PhSCl and elimination of HCl. Oxidation and reaction with trimethyl phosphite gave the primary alcohol (209) stereospecifically in 75% overall yield. Use has been made of this procedure in the synthesis of solanesol (C45) from three C15 units.The tosyl derivative of the hydroxylated farnesol (211) reacts with the bromide (212) prepared from (213) to give the C30 product (215), the bromide (216) of which, after further reaction with (214), affords the solanesol derivative (217) and thence solanesol (205). 

Undecaprenol (bactoprenol) from Salmonella contains eleven isoprene units, and two irons and nine cis double bonds In the form of undecaprenyl phosphate, it acts as a carrier of carbohydrate residues in the biosynthesis of bacterial antigenic polysaccharides synthesis of Murein (see) also depends on undecaprenyl phosphate. In eukaryotes the Dolichol phosphates (see) function in the transfer of carbohydrate residues in the synthesis of glycoproteins and glycoli-pids. Probably the long lipid chains of these P serve to anchor them in membranes, while the phosphate group acts as a carrier by protruding into the cytoplasm. It is not known whether all P. function as carbohydrate carriers. The structural relationship between solanesol and plastoquinone-9 and ubiquinone-9, and the joint occurrence of these compounds suggest a precursor role for P. Biosynthesis of P. proceeds from mevalonic acid and the conformation of all double bonds is predetermined in early precursors. 

Yu X, Wang S, Chen F. Solid-phase synthesis of solanesol. 

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