Lipase catalysed reactions of terpenoids : formation of hemiacetal esters : resolution of cryptone and its transformation to cadinenes
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
During attempted enzyme-catalysed resolution of sterically hindered secondary alcohols, hemiacetals and their esters were unexpectedly detected. Hemiacetal esters are reactive compounds that decompose to alcohol, aldehyde and acid under ordinary work-up conditions i.e. in contact with water, acid, or silica gel. Thus, the presence of these side products might decrease the enantiomeric excess of the residual alcohol after workup of a lipase-catalysed resolution. The formation of these hemiacetal esters were further studied using both terpenoid and non-terpenoid substrate alcohols, various acyl donors, and lipases. The prerequisite for their formation is the presence of a sterically hindered substrate alcohol, an aldehyde or an aldehyde releasing acyl donor, and a lipase (PCL-L6, PCL-PS and CAL-B).
Enantioselective synthesis of (S)- and (R)-cryptone was performed via a ring closing metathesis (RCM) of (S)- and (R)-6-isopropyl-1,7-octadien-3-one. The stereochemistry was induced by using pseudoephedrine as chiral auxiliary in an alkylation reaction which provided a chiral octadienone. Problems with removal of the RCM-catalyst resulted in low yields and low enantiomeric purity. In an alternative approach, racemic cryptone was subjected to conjugate addition with thiophenol followed by reduction to the corresponding alcohol. Lipase-catalysed resolution of this alcohol yielded, after oxidation and elimination, (R)- and (S)- cryptone with 76% and 98% ee, respectively.
Marine fouling of immersed objects is a serious problem. Many coatings contain effective antifouling compounds having the drawback of being toxic to the marine environment. The marine natural product 10-isocyano-4-cadinene is a potentially non-toxic antifouling agent against the barnacle Balanus amphitrite and therefore an interesting target for organic synthesis. Cryptone was used as a starting material in attempted syntheses of this compound and other similar model compounds.
Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , 41 p.
Trita-IOK, ISSN 1100-7974 ; 05:99
terpenoid, lipase, resolution, hemiacetal, hemiacetal ester, enantioselective, synthesis, cryptone, cadinene
IdentifiersURN: urn:nbn:se:kth:diva-588ISBN: 91-7178-225-7OAI: oai:DiVA.org:kth-588DiVA: diva2:14519
2006-01-27, Sal 0102, Mittuniversitetet, 10:00
Almqvist, Fredrik, Doc
QC 201009012006-01-162006-01-162010-09-01Bibliographically approved
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