Enzyme-Mediated Syntheses of the Enantiomers ofγ-Irones

Abstract

An enzymatic approach to the synthesis of all the possible stereoisomers of (E) and (Z), cis and trans-girones in enantiomerically pure form from commercial Irone Alpha ¾ is described. A very efficient resolution of racemic trans-g-irone, affording both the enantiomers in high ee and chemical purity, is also presented. Olfactory evaluation of ()-and (À)-3b and full configuration assignment of the irone isomers contained in samples of Italian iris oil are reported.

Electrophilic Cyclization of 1,6‐Dienes Containing an Allylsilane Moiety − Enantioselective Synthesis of cis‐ and trans‐γ‐Irone

“…Most Iris oils contain the three α‐, β‐, and γ‐double‐bond isomers 1 − 3 in different proportions 2. In the natural oils cis ‐α‐irone and cis ‐γ‐irone are the major components, but trans ‐α‐irone is also found and, on one occasion, traces of (−)‐ trans ‐γ‐irone have been detected 2b, 2f. In addition, enantiomeric irones can be isolated from Iris plants of different geographical origin.…”

“…In the γ‐series, (−)‐(2 S ,6 R )‐ cis ‐irone ( 4 ) is considered to have the strongest and finest aroma of the four isomers,3,4l whereas the threshold value of (−)‐(2 S ,6 S )‐ trans ‐irone ( 5 ) is four times higher than that of the (+)‐enantiomer 2f…”

Two easy photochemical methods for the conversion of commercial ionone alpha into regioisomerically enriched γ‐ionone and γ‐dihydroionone

“…This double bond is only involved in an E/Z isomerization process. 14,15 On the other hand, when α-ionone or α-dihydroionone are treated with oxygen and irradiated with visible light in the presence of methylene blue (singlet oxygen), the 4-hydroperoxyγ-ionone derivatives are formed regioselectively. 16,17 As shown in Scheme 2, we exploited the latter acquired methodologies in the regioselective synthesis of 3 and 6.…”

Stereoselective Enzymatic Acylations (Transesterifications)

“…Brenna et al reported an enzymatic approach to the synthesis of all the possible stereoisomers of (E) and (Z), cis and trans-γ-irones in enantiomerically pure form [82]. A very efficient resolution of γ-irol 8, Fig.…”