| Abstract: | A chiral economic synthesis of (R)- and (S)-muscone using the cyclofragmentation of epoxysulfones Starting with isobutyric acid (2) and using a microbiological oxidation with pseudomonas putida (S)-β-hydroxy-iso-butyric acid (3) has been prepared. From this /pseudosymmetrical: (see text) intermediate the two enantiomeric bromo derivatives 8 (R) and 20 (S) have been synthesized (cf. scheme 4) by altering the sequence of the reactions (cf. scheme 3). A Grignard reaction starting from the two bromo compounds 8 and 20 and from cyclododecanone 1 produced after hydrogenolysis the two enantiomeric dialcohols 9 and 21 (1 + 8 → 9, 1 + 20 → 21 , cf. scheme 5). The subsequent transformations led to the two enantiomeric olefin derivatives 12 and 24 . Oxidation of 12 with peracid produced a mixture of the two epoxy-sulfones 13 and 14 (cf. scheme 6). The olefin-derivative 24 was oxidized to the corresponding mixture of 25 and 26 . A one pot cyclofragmentation (cf. 4] and scheme 6) produced a mixture of (E)- and (Z)-3-methylcyclopentadec-4-en-1-one (13 + 14 → 15 + 16, 25 + 26 → 27 + 28) . The final hydrogenation led to natural (R)- and unnatural (S-muscone (3-methylcyclopentadecanone). The achiral starting material has been transformed to the desired optically active target products without loss of material with undesired absolute configuration. The authors used the notion of chiral economic synthesis to characterize synthetic sequences with the above mentioned features. |
