Chemoenzymatic Synthesis of Homochiral (R)- and (S)-Karahanaenol from (R)-Limonene

Abstract

Terpinolene oxide, a monoterpene belonging to the p-menthane group, is easily derived from naturally abundant (R)-limonene. It was isomerized with montmorillonite clay catalyst to karahanaenone (2,2, 5-trimethylcyclohept-4-en-1-one) by ring enlargement. The enantiomers of the corresponding alcohol, karahanaenol (2,2, 5-trimethylcyclohept-4-en-1- ol), known for their individual organoleptic properties, were resolved through Pseudomonas cepacia lipase mediated enantiospecific alcoholysis of its acetate derivative.

Pyrococcus furiosus glyceraldehyde 3‐phosphate oxidoreductase has comparable W6+/5+ and W5+/4+ reduction potentials and unusual [4Fe‐4S] EPR properties

“…No reduction to W 4 2 was found. W 5 1 was not found in the dye-mediated redox titration. The S = 3/2 and S = 1/2 signals attributed to [4Fe-4S] 1 have the same midpoint potential.…”

“…This signal has not been reported previously. The latter signal will be designated W 5 1 , and the other, with the lower quantity, W 5 2 . The designations used in the literature for FOR and AOR (i.e.…”

“…The E m values of the W 5 1 species can be seen in Table 2 and are consistent with two subsequent one-electron reductions from W 6 to W 4 . The maximum quantity of W 5 1 is 0.30 spins/ molecule while the quantity of the W 5 2 species is unchanged during the titration and amounts to only 0.09 spins/mol (cf. Fig.…”

“…Contrarily, FOR and AOR have a broader in vitro speci¢city for short chain and longer chain aldehydes [5,6]. The sequence homology with AOR (15% identity) [7] and FOR (23% identity) [5] is relatively low compared to the homology between AOR and FOR (40% identity) [5]. GAPOR has not been characterized in detail spectroscopically.…”

Biotechnological Flavour Generation

“…Many subsequent papers and patents confirm the competitiveness and industrial usefulness of this mature bioprocess. This classical approach was followed to resolve (R)-and (S)-karahanaenol produced from ring enlargement of limonene epoxide (Roy, 1999). The racemic monoterpenol acetate was resolved using a Pseudomonas cepacia lipase, and the 4R-isomer alcohol was preferentially obtained through alcoholysis (Fig.…”