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Total synthesis of both enantiomers of copalol via optical resolution of a general synthetic intermediate for drimane sesquiterpenes and labdane diterpenes



Total synthesis of both enantiomers of copalol via optical resolution of a general synthetic intermediate for drimane sesquiterpenes and labdane diterpenes



Tetrahedron 56(43): 8443-8450, 20 October



The total synthesis of both enantiomers of copalol (6) was accomplished via the optical resolution of a racemic diol ((+-)-4) which is a general synthetic intermediate for drimane sesquiterpenes and labdane diterpenes. Esterification between (+-)-4 and Boc-L-proline gave the diastereomeric pair of monoesters (5a and 5b) which could be readily separated by flash column chromatography. PDC-oxidation of the resolved 5a and 5b, and subsequent beta-elimination gave optically active enones (9 and ent-9). Both enones were respectively converted into (+)-6 in 36% yield and (-)-6 in 26% yield in five steps: (1) Sakurai reaction (TiCl4-promoted conjugate addition of allylsilane), (2) Wittig methylenation, (3) Wacker oxidation, (4) Horner-Emmons reaction, and (5) DIBAL-H reduction.

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Accession: 011576641

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DOI: 10.1016/s0040-4020(00)00791-2


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