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Enzyme‐Mediated Preparation of (+)‐ and (–)‐ cis ‐ α ‐Irone and (+)‐ and (–)‐ trans ‐ α ‐Irone
Author(s) -
Brenna Elisabetta,
Fuganti Claudio,
Fronza Giovanni,
Malpezzi Luciana,
Righetti Annalisa,
Serra Stefano
Publication year - 1999
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(19991215)82:12<2246::aid-hlca2246>3.0.co;2-3
Subject(s) - chemistry , enzyme , stereochemistry , biochemistry , combinatorial chemistry
The preparation of (−)‐ and (+)‐ trans ‐ α ‐irone ( 1a and 1b , resp.) and of (+)‐ and (−)‐ cis ‐ α ‐irone ( 1c and 1d , resp.) from commercially available Irone alpha ® is reported. The relevant step in the synthetic sequence is the initial chromatographic separation of crystalline (±)‐4,5‐epoxy‐4,5‐dihydro‐ cis ‐ α ‐irone ((±)‐ 5 ) from oily (±)‐4,5‐epoxy‐4,5‐dihydro‐ trans‐ α ‐irone ((±)‐ 4 ). The latter was subsequently converted, after NaBH 4 reduction, into the crystalline 3,5‐dinitrobenzoate ester (±)‐ 8 , thus allowing a complete separation of the two corresponding diastereoisomeric alcohol derivatives. Suitable enantiomerically pure precursors of the desired products 1a – d were obtained by kinetic resolution of the racemic allylic alcohols derived from (±)‐ 5 and (±)‐ 8 , mediated by lipase PS ( Amano ). The last steps consisted of MnO 2 oxidation and removal of the epoxy moiety with Me 3 SiCl/NaI in MeCN. External panel olfactory evaluation showed that (−)‐ cis ‐ α ‐irone ( 1d ) has the finest and most distinct `orris butter' character.