Lipase–triethylamine-mediated dynamic transesterification of a tricyclic acyloin having a latent meso-structure: a new route to optically pure oxodicyclopentadiene

Taniguchi, Takahiko; Ogasawara, Kunio

doi:10.1039/a702910a

Cited by 20 publications

(4 citation statements)

References 12 publications

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“…This indicates that the lipase is activated by trioctylamine although the effect is not so profound. A similar behavior for the lipase-catalyzed enantioselective transesterification of diols by using an organic solvent containing triethylamine as the reaction medium has been reported (Taniguchi and Ogasawara, 1997;Theil et al, 1991a,b). A simple and practical way to consider this effect is to add an empirical term of [9.76 + 3.15(B)]/[9.76 + (B)] to the first term on the right-hand side of equations (6) and (7).…”

Section: Effects Of Substrate and Trioctylamine Concentration On The supporting

confidence: 53%

Lipase-catalyzed dynamic resolution of naproxen 2,2,2-trifluoroethyl thioester by hydrolysis in isooctane

Chang

Tsai

Kuo

1999

Biotechnol. Bioeng.

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Section: Effects Of Substrate and Trioctylamine Concentration On The supporting

confidence: 53%

Lipase-catalyzed dynamic resolution of naproxen 2,2,2-trifluoroethyl thioester by hydrolysis in isooctane

Chang

Tsai

Kuo

1999

Biotechnol. Bioeng.

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“…Thus, a (in situ) racemization of the remnant substrate under KR conditions would theoretically lead to a 100% yield (Scheme ). In some (few) cases, the in situ base-mediated racemization of the substrate can be applied, as reported by Taniguchi and Ogasawara for the resolution of different tricyclic acyloins, by using a Burkholderia cepacia lipase . In other cases, efficient two-compartment DKR processes have been developed, involving Candida antarctica lipase B (CALB) as biocatalyst for the enantioselective substrate transesterification in a first compartment, and the simultaneous racemization of the remnant alcohol mediated by Amberlyst 15 in a spatial-separated compartment (Scheme ).…”

Section: Hydrolase-catalyzed (In Situ) Dynamic Kinetic Resolutions (D...mentioning

confidence: 99%

Biocatalytic Strategies for the Asymmetric Synthesis of α-Hydroxy Ketones

et al. 2009

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T he development of efficient syntheses for enantiomerically enriched R-hydroxy ketones is an important research focus in the pharmaceutical industry. For example, R-hydroxy ketones are found in antidepressants, in selective inhibitors of amyloid-β protein production (used in the treatment of Alzheimer's), in farnesyl transferase inhibitors (Kurasoin A and B), and in antitumor antibiotics (Olivomycin A and Chromomycin A3). Moreover, R-hydroxy ketones are of particular value as fine chemicals because of their utility as building blocks for the production of larger molecules. They can also be used in preparing many other important structures, such as amino alcohols, diols, and so forth. Several purely chemical synthetic approaches have been proposed to afford these compounds, together with some organocatalytic strategies (thiazolium-based carboligations, proline R-hydroxylations, and so forth). However, many of these chemical approaches are not straightforward, lack selectivity, or are economically unattractive because of the large number of chemical steps required (usually combined with low enantioselectivities).In this Account, we describe three different biocatalytic approaches that have been developed to efficiently produce R-hydroxy ketones:(i) The use of thiamine diphosphate-dependent lyases (ThDP-lyases) to catalyze the umpolung carboligation of aldehydes. Enantiopure R-hydroxy ketones are formed from inexpensive aldehydes with this method. Some lyases with a broad substrate spectrum have been successfully characterized. Furthermore, the use of biphasic media with recombinant whole cells overexpressing lyases leads to productivities of ∼80-100 g/L with high enantiomeric excesses (up to >99%).(ii) The use of hydrolases to produce R-hydroxy ketones by means of (in situ) dynamic kinetic resolutions (DKRs). Lipases are able to successfully resolve racemates, and many outstanding examples have been reported. However, this approach leads to a maximum theoretical yield of 50%. As a means of overcoming this problem, these traditional lipase-catalyzed kinetic resolutions are combined with racemization of remnant substrate, which can be done in situ or in separate compartments. Examples showing high conversions (>90%) and enantiomeric excesses (>99%) are described.(iii) Whole-cell redox processes, catalyzed by several microorganisms, either by means of free enzymes (applying a cofactor regeneration system) or by whole cells. Through the use of redox machineries, different strategies can lead to high yields and enantiomeric excesses. Some enantiopure R-hydroxy ketones can be formed by reductions of diketones and by selective oxidations of vicinal diols. Likewise, some redox processes involving sugar chemistry (involving R-hydroxy ketones) have been developed on the industrial scale. Finally, the redox whole-cell concept allows racemizations (and deracemizations) as well.These three strategies provide a useful and environmentally friendly synthetic toolbox. Likewise, the field represents an illustrative example of how b...

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“…As can be seen, oxidation of 467 with Pb(OAc) 4 in toluene afforded the desired lactone 468 in 92% yield 197 Taniguchi and Ogasawara synthesized the versatile chiral oxodicyclopentadiene 470. The treatment of diol 469 with NaIO 4 and NaOH yielded the optically active (−)-oxodicyclopentadiene (470) 198 .…”

Section: A Oxidative Cleavagementioning

confidence: 99%