Chiral compounds 2,3 -Wittig rearrangement

In order to establish the correct absolute stereochemistry in cyclopentanoid 123 (Scheme 10.11), a chirality transfer strategy was employed with aldehyde 117, obtained from (S)-(-)-limonene (Scheme 10.11). A modified procedure for the conversion of (S)-(-)-limonene to cyclopentene 117 (58 % from limonene) was used [58], and aldehyde 117 was reduced with diisobutylaluminium hydride (DIBAL) (quant.) and alkylated to provide tributylstannane ether 118. This compound underwent a Still-Wittig rearrangement upon treatment with n-butyl lithium (n-BuLi) to yield 119 (75 %, two steps) [59]. The extent to which the chirality transfer was successful was deemed quantitative on the basis of conversion of alcohol 119 to its (+)-(9-methyI mande I ic acid ester and subsequent analysis of optical purity. The ozonolysis (70 %) of 119, protection of the free alcohol as the silyl ether (85 %), and reduction of the ketone with DIBAL (quant.) gave alcohol 120. Elimination of the alcohol in 120 with phosphorus oxychloride-pyridine... 

An asymmetric total synthesis of eupomatilones has been reported with the two chiral centres constructed enantioselectively by the asymmetric [2,3]-Wittig rearrangement of highly oxygenated biaryl compounds, using a bis(oxazoline) chiral ligand... 

This approach has been applied to the synthesis of peptide isosteres, compounds that have the same shape as peptides but lack the amide link. In this case 99 it is replaced by an E-alkene. The starting material 97 is made from the natural amino acid leucine and the Wittig-Still [2,3] shift on 98 rearranges this into an E-alkene flanked by two chiral centres 99. 

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