Protection of Alcohols Using 2‐Benzyloxy‐1‐Methylpyridinium Trifluoromethanesulfonate: Methyl (
            <scp>R</scp>
            )‐(−)‐3‐Benzyloxy‐2‐Methyl Propanote

Poon, Kevin W. C.; Albiniak, Philip A.; Dudley, Gregory B.

doi:10.1002/0471264229.os084.29

Cited by 18 publications

(13 citation statements)

References 6 publications

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“…The absolute configuration of 3b was determined by comparison with a published chiral HPLC analysis (Chiralcel OD-H 0.46 25 cm, 98:2 heptane:2-propanol mobile phase at 1.5 mL min À1 flow): the (R)-enantiomer eluted at 3.88 min, the (S)-enantiomer eluted at 4.17 min. [32] Supporting Information…”

Section: Determination Of Absolute Configurationsmentioning

confidence: 99%

Asymmetric Synthesis of (R)‐3‐Hydroxy‐2‐methylpropanoate (‘Roche Ester’) and Derivatives via Biocatalytic CC‐Bond Reduction

et al. 2010

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Enoate reductases from the old yellow enzyme family were employed for the asymmetric bioreduction of methyl 2-hydroxymethylacrylate and its O-allyl, O-benzyl and O-TBDMS derivatives to furnish (R)-configurated methyl 3-hydroxy-2-methylpropionate products in up to > 99% ee Variation of the O-protective group had little influence on the stereoselectivity, but a major impact on the reaction rate.Keywords: biocatalysis; C=C-bioreduction; enoate reductase; old yellow enzyme; substrate engineeringThe asymmetric reduction of C=C bonds creates (up to) two chiral carbon centres and is thus one of the most widely employed strategies for the production of chiral materials. The biocatalytic variant, which is applicable to activated alkenes bearing an electron-withdrawing substituent is catalysed by enoate reductases [EC 1.3.1.X], [1,2] which are members of the old yellow enzyme (OYE) family.[3] Over the past few years, increasing attention has been devoted to these flavoproteins [4] in view of their substrate scope, [5] encompassing a,b-unsaturated carbonyl compounds (such as enals and enones), as well as carboxylic acids and derivatives thereof (such as esters, cyclic imides, nitriles, lactones) and nitroalkenes. As a rule of thumb, the degree of activation of the C=C-bond exerted by the electron-withdrawing effect of the activating substituent goes hand in hand with the substrate acceptance, which ensures generally fast reaction rates for enals, enones and nitroalkenes, whereas (di)carboxylic acids and esters are transformed more slowly.To illustrate the importance of this enzyme class for asymmetric synthesis, we aimed at their applicability for an industrially relevant product, that is, (R)-3-hydroxy-2-methylpropanoate, which is commonly denoted as the Roche ester. The latter is a popular chiral building block for the synthesis of vitamins (e.g., a-tocopherol [6] ), fragrance components (e.g., muscone [7] ), and antibiotics (e.g., calcimycin, [8] palinurin, [9] rapamycin, [10] 13-deoxytedanolide, [11] dictyostatin [12] ) and natural products (e.g., spiculoic acid A [13] ). Classical methods for its preparation include the diastereoselective addition of non-racemic alcohols as chiral auxiliaries, [14] the transformation of a chiral homoallylic acetate [15] or involve aldol condensation [16] and -most prominent -the transition metal-catalysed asymmetric hydrogenation of acrylate esters using Rh [17] (ee up to 99%) or Ru [18] (ee up to 94%). For the biocatalytic synthesis of the Roche ester only few examples are reported: the stereoselective oxidation of 2-methyl-1,3-propanediol by Gluconobacter and Acetobacter spp. [19] (ee up to 97%), the asymmetric reduction of ethyl 4,4-dimethoxy-3-methylcrotonate using bakers yeast [20] and the stereoseletive (formal) b-hydroxylation of isobutyric acid using Pseudomonas putida (ATCC 21244).[21] All of these biotransformations were performed using whole (fermenting) microbial cells with several enzymes being involved. Only recently, was it shown that a non-flavin NADH-dependen...

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Section: Determination Of Absolute Configurationsmentioning

confidence: 99%

Asymmetric Synthesis of (R)‐3‐Hydroxy‐2‐methylpropanoate (‘Roche Ester’) and Derivatives via Biocatalytic CC‐Bond Reduction

et al. 2010

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“…The reaction preceded very well for primary benzyl alcohols as shown in entries 2–4 (Table 2). Interestingly cinnamyl alcohol (entry 5), which is a challenging substrate for some etherification reagents, 18d gave an 88% yield of the corresponding ether 14 . Propargyl alcohol also proved an excellent substrate, and gave the corresponding ether 15 in 97% yield.…”

Section: Resultsmentioning

confidence: 99%

“…Exemplifying these reagents, Dudley has reported the benzylation of alcohols using benzyloxy pyridinium triflates in refluxing α,α,α-trifluorotoluene. 13, 18 Similar systems have also been developed for the formation of PMB ethers utilizing a lepidine derivative as the benzyl transfer reagent. 19 The quaternary pyridinium salts may also be generated in situ by the addition of methyl triflate to an appropriately functionalized pyridine or quinoline system.…”

Section: Introductionmentioning

confidence: 99%

Formation of DPM ethers using O-diphenylmethyl trichloroacetimidate under thermal conditions

et al. 2016

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Alcohols are effectively converted to their corresponding diphenylmethyl (DPM) ethers by reaction with O-diphenylmethyl trichloroacetimidate in refluxing toluene without the requirement of a catalyst or other additive. A number of acid and base sensitive substrates were protected in excellent yield using this new method without disturbing pre-existing functionality present in these molecules. This reaction is the first example of the formation of an ether from stoichiometric amounts of a trichloroacetimidate and an alcohol without the addition of a Brønsted or Lewis acid catalyst.

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“…Into a solution of 3c (103 μL, 0.5 mmol) in benzotrifluoride (2 mL) was added 2-benzyloxy-1-methylpyridinium triflate xxi (349 mg, 1 mmol) and MgO (40 mg, 1 mmol). The reaction mixture was stirred at 83 °C.…”

Section: Methodsmentioning

confidence: 99%

DIBAL-Mediated Reductive Transformation of trans-Dimethyl Tartrate Acetonide into ε-Hydroxy α,β-Unsaturated Ester and Its Derivatives

et al. 2011

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Protection of Alcohols Using 2‐Benzyloxy‐1‐Methylpyridinium Trifluoromethanesulfonate: Methyl ( R )‐(−)‐3‐Benzyloxy‐2‐Methyl Propanote

Abstract: Benzyl alcohol 2‐Chloropyridine 2‐Benzyloxypyridine 2‐Benzyloxy‐1‐methylpyridinium trifluoromethanesulfonate Methyl (R)‐(−)‐3‐benzyloxy‐2‐methyl propanoate Magnesium oxide Methyl (R)‐(−)‐3‐hydroxy‐2‐methyl propionate

Cited by 18 publications

References 6 publications

Asymmetric Synthesis of (R)‐3‐Hydroxy‐2‐methylpropanoate (‘Roche Ester’) and Derivatives via Biocatalytic CC‐Bond Reduction

Asymmetric Synthesis of (R)‐3‐Hydroxy‐2‐methylpropanoate (‘Roche Ester’) and Derivatives via Biocatalytic CC‐Bond Reduction

Formation of DPM ethers using O-diphenylmethyl trichloroacetimidate under thermal conditions

DIBAL-Mediated Reductive Transformation of trans-Dimethyl Tartrate Acetonide into ε-Hydroxy α,β-Unsaturated Ester and Its Derivatives

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