Enzymatic desymmetrisation of a cyclopentane-triol deriviative; enantiomerically pure cyclopentane-triol derivatives SyntheticPage 27 (2001)
Submitted 4th Jul 2001, published 5th Jul 2001
zac etheridge
([email protected]),
A contribution from the Caddick
Chemicals Used
trans,trans-3-Acetoxy-5-hydroxy-4-t-butyldimethylsiloxy-cyclopentene (92mg)
Lipase AK (65mg, generously provided by Amano Enzyme Co.)
pH 7 phosphate buffer (made up from buffer tablets available from Fisher)
Procedure
To the cyclopentene derivative is added the buffer followed by Lipase AK. The suspension is stirred at 30C for 70-80 hours until completion (TLC), then extracted 3 times with ethyl acetate, washed with water, dried over magnesium sulphate, filtered and concentrated. Purification is by column chromatography eluting with 15-20% EtOAc/PE
Author's Comments
Enzymatic desymmetrisations are a very useful way of producing optically pure products; the advantage over a kinetic resolution is the potential for 100% yield, as compared with a theoretical maximum of 50% for a kinetic resolution. The downside is the substrate must have an axis of symmetry. In this instance, the desired enantiomer is obtained by selective hydrolysis of one of the acetates, but the opposite enantiomer can be obtained by making the substrate as its meso diol (ie removing the acetates) and then reacting it with vinyl acetate in the presence opf the same enzyme. Lipase AK seems to be quite specific to this reaction, but Lipase PS, also obtainable form Amano Enzyme Co. works with a wider range of substrates and is suitable for kinetic resolutions of a number of secondary alcohols, an example of which will appear in synthetic pages in due course.
Data
1HNMR (300MHz, CDCl3) 0.00 (3H, s), 0.03 (3H, s), 0.81 (9H, s), 1.75 (1H, d), 1.98 (3H, s), 4.04 (1H, t), 4.39 (1H, s), 5.23 (1H, s), 5.72 (1H, d, J=6.0), 5.83 (1H, d, J=6.0)
[a]30D +61.5°
Lead Reference
Toyama, K.; Iguchi, S.; Oishi, T.; Hirama, M.; Synlett, 1995, 1243.
Other References
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