Camphorsulphonic acid-derived

An alternate strategy for the synthesis of epoxides is by the reaction of sulfonium ylides with aldehydes. Aggarwal and coworkers have developed a catalytic asymmetric variant of this process using camphorsulphonic acid-derived sulfonium ylides such as (4.130) and (4.131). °... 

Le Bel s resolution of a quaternary ammonium compound l abcdX. was doubtful, but Pope, S. J. Peachey, and A. W. Harvey resolved a quaternary nitrogen compound by means of camphorsulphonic acid. S. Smiles and Pope and Peachey prepared optically active sulphur compounds. Pope and Neville a selenium compound, and Pope and Peachey tin compounds. A very simple compound, CHCl SOgH), was resolved by Pope and Read. Pope and C. S. Gibson prepared alkyl derivatives of gold, and Pope and Peachey of platinum. 

Despite numerous syntheses of Voriconazole (10) were documented, they all followed the same synthetic strategy, namely, addition of anion 221 to ketone 222, followed by isolation of necessary diastereomeric pair and its resolution with 10-camphorsulphonic acid (Schane 53). Three different approaches were used for the generation of anion 221 or the corresponding organometallic species. First of them relied on deprotonation of the pyrimidine derivative 222 (prepared from the fluorinated keto ester 223 or dichloro derivative 93) by strong bases such as LDA (Scheme 54) [183-189]. 

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