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A ring-closing metathesis-based approach to (+)- and (-)-cryptone
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
(English)Manuscript (Other academic)
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-8991OAI: oai:DiVA.org:kth-8991DiVA: diva2:14516
Note
QC 20100901Available from: 2006-01-16 Created: 2006-01-16 Last updated: 2010-09-01Bibliographically approved
In thesis
1. Lipase catalysed reactions of terpenoids : formation of hemiacetal esters : resolution of cryptone and its transformation to cadinenes
Open this publication in new window or tab >>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)
Abstract [en]

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.
Series
Trita-IOK, ISSN 1100-7974 ; 05:99
Keyword
terpenoid, lipase, resolution, hemiacetal, hemiacetal ester, enantioselective, synthesis, cryptone, cadinene
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-588 (URN)91-7178-225-7 (ISBN)
Public defence
2006-01-27, Sal 0102, Mittuniversitetet, 10:00
Opponent
Note
QC 20100901Available from: 2006-01-16 Created: 2006-01-16 Last updated: 2010-09-01Bibliographically approved

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