- Ketoreductase/Transaminase, One-Pot, Multikilogram Biocatalytic Cascade Reaction
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A biocatalytic cascade to produce tert-butyl ((2R,4R)-2-methyltetrahydro-2H-pyran-4-yl)carbamate 6 has been demonstrated at the multikilogram scale. In this reaction, a racemic ketone is resolved by reducing the undesired ketone using a ketone reductase (KRED). The reduction is stereospecific for the 2-position of substrate (2S)-ketone leaving the (2R)-ketone unreacted. After the (2S)-ketone has been depleted, a transaminase is added to catalyze the enantioselective transamination of the ketone, resulting in formation of the (2R, 4R)-amine 6. The product is recovered from the aqueous reaction after Boc protection.
- Burns, Michael,Bi, Wenying,Kim, Hui,Lall, Manjinder S.,Li, Chao,O'Neill, Brian T.
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- Routes for the synthesis of (2S)-2-methyltetrahydropyran-4-one from simple optically pure building blocks
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Routes to (2S)-2-methyltetrahydropyran-4-one of high optical purity starting from readily available chiral pool precursors and suitable for large-scale manufacture are described. In one approach, the key step is cyclisation of (S)-5-hydroxyhex-1-en-3-one, derived either from an alkyl (S)-3-hydroxybutyrate or (S)-propylene oxide. Formation of the tetrahydropyran ring directly via an intramolecular oxy-Michael reaction under acid-catalysed conditions resulted in loss of optical purity, whereas proceeding through the intermediate (2S)-2-methyl-2,3-dihydropyran-4-one, via an oxidative Pd-catalysed ring closure, followed by hydrogenation of the alkenyl bond, preserved the optical purity. An alternative approach to (2S)-2-methyl-2,3-dihydropyran-4-one is also reported, again starting from an alkyl (S)-3-hydroxybutyrate by elaboration to a carbonyl-protected (6S)-6-methyl-5,6-dihydropyran-2,4-dione derivative, followed by partial reduction and dehydration. Alternatively, the carbonyl group can be reduced out completely in one step to furnish (2S)-2-methyltetrahydropyran-4-one directly after deprotection.
- Anderson, Kevin R.,Atkinson, Stephanie L. G.,Fujiwara, Takahiro,Giles, Melvyn E.,Matsumoto, Takaji,Merifield, Eric,Singleton, John T.,Saito, Takao,Sotoguchi, Tsukasa,Tornos, James A.,Way, Edward L.
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