- Lipase-Catalyzed Kinetic Resolution on Solid-Phase via a "Capture and Release" Strategy
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The lipase-catalyzed kinetic resolution of (R/S)-3-phenylbutyric acid 2 using solid-supported cyclohexane-1,3-dione (CHD) 6 is described. In each case the predominant enantiomer observed, after cleavage from the resin, was (R)-(?)-3-phenylbutyric acid (R)-2 (ee > 99%) rather than the expected (S)-enantiomer of 2. This observation is in contrast to the fact that Chromobacterium viscosum lipase shows high enantiospecificity for the (S)-enantiomer in the corresponding solution-phase hydrolysis reactions. The (R)-acyl group was subsequently released from the resin by NaOH hydrolysis, and the yield of the reaction could be improved by triple acylation of the resin. Copyright
- Humphrey, Cara E.,Turner, Nicholas J.,Easson, Morag A. M.,Flitsch, Sabine L.,Ulijn, Rein V.
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Read Online
- Synthesis of chiloglottones - Semiochemicals from sexually deceptive orchids and their pollinators
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A five-step synthesis of monoalkyl- and 2,5-dialkyl-1,3-cyclohexanediones (1) is described via a sequence involving sequential Birch reductions and alkylations from the readily accessible and inexpensive starting material, 3,5-dimethoxybenzoic acid. Two approaches were considered in which alkylation at C-2 occurs either prior or subsequent to the proposed reduction. The successful route, in which Birch reduction of a 3-alkyl resorcinol derivative (3) precedes alkylation was applied in the synthesis of chiloglottone 1 (1dc), in 58% overall yield. Chiloglottone 1 is a member of a new class of natural products, representing a known sex pheromone of the thynnine wasp Neozeleboria cryptoides and pollinator attractant in the Australian sexually deceptive orchid genus Chiloglottis. The synthetic homologues were assessed for their biological activity via electroantennographic detection.
- Poldy, Jacqueline,Peakall, Rod,Barrow, Russell Allan
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supporting information; experimental part
p. 4296 - 4300
(2009/12/06)
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- Solid-supported cyclohexane-1,3-dione (CHD): A "capture and release" reagent for the synthesis of amides and novel scavenger resin
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A three-step synthesis of cyclohexane-1,3-dione (CHD) resin 6 on polystyrene resin is described. Resin 6 was used to prepare an amide library of high purity by microwave-assisted serial "capture and release" and can be recycled for this purpose. High-loading CHD resin 10 was also shown to scavenge allyl cations in solution.
- Humphrey, Cara E.,Easson, Morag A. M.,Tierney, Jason P.,Turner, Nicholas J.
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p. 849 - 852
(2007/10/03)
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- The Birch reduction - Dialkylation reaction of aromatic carboxylic acids. Identification of NaNH2 as the base responsible for the second alkylation
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The Birch reduction-alkylation of 3,5-dimethoxybenzoic acid with excesses Na and EDtBr gives 1,4-diethyl-3,5-dimethoxy-2,5-cyclohexadiene carboxylic acid, 3. The base responsible for the alkylation at C-4 has been identified as NaNH2, generated
- Guzman,Castanedo,Maldonado
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p. 1001 - 1012
(2007/10/02)
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- Preparation of Some 1-Alkyl-4-3-hydroxy-5-oxocyclohex-3-ene-1-carboxylic Acid Ester and Amide Herbicides by Reductive Alkylation of 3,5-Dimethioxybenzoic Acid
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Reductive alkylation of 3,5-dimethoxybenzoic acid with haloalkanes afforded the 1-alkyl-3,5-dimethoxycyclohexa-2,5-diene-1-carboxylic acid derivatives (3a-e) which, upon esterification and hydrolysis furnished methyl 1-alkyl-3-hydroxy-5-oxocyclohex-3-ene-1-carboxylate derivatives (4f-j).Reaction of (4f-j) with butyric anhydride gave methyl 1-alkyl-4-butyryl-3-hydroxy-5-oxocyclohex-3-ene-1-carboxylate derivatives (6a-e) which were converted into methyl 1-alkyl-4--3-hydroxy-5-oxocyclohex-3-ene-1-carboxylate derivatives (2a-e).Similarly, the oximeO-ether derivative (2f) was prepared from the amide (4l), obtained from reaction of (3b) with N,N'-carbonyldiimidazole and dimethylamine followed by hydrolysis.
- Liepa, Andris J.,Wilkie, John S.,Winzenberg, Kevin N.
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p. 1217 - 1225
(2007/10/02)
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