- Asymmetric Synthesis of a Key Dextromethorphan Intermediate and Its Analogues Enabled by a New Cyclohexylamine Oxidase: Enzyme Discovery, Reaction Development, and Mechanistic Insight
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(S)-1-(4-Methoxybenzyl)-1,2,3,4,5,6,7,8-octahydroisoquinoline [(S)-1-(4-methoxybenzyl)-OHIQ, (S)-1a] is a key synthetic intermediate in the industrial production of dextromethorphan, one of the most widely used over-the-counter antitussives. We report here that a new cyclohexylamine oxidase discovered by genome mining, named CHAOCCH12-C2, was able to completely deracemize 100 mM 1a under Turner's deracemization conditions to afford (S)-1a in 80% isolated yield and 99% ee at a semipreparative scale (0.4 mmol). When this biocatalytic reaction was scaled up to a gram scale (5.8 mmol), without reaction optimization (S)-1a was still isolated in 67% yield and 96% ee. The relatively higher kcat determined for CHAOCCH12-C2 was rationalized as one major factor rendering this enzyme capable of oxidizing 1a effectively at elevated substrate concentrations. Protein sequence alignment, analysis of our co-crystal structure of CHAOCCH12-C2 complexed with the product 1-(4-methoxybenzyl)-3,4,5,6,7,8-hexahydroisoquinoline [1-(4-methoxybenzyl)-HHIQ, 2a], and the structure-guided mutagenesis study together indicated L295 is one of the critical residues for this efficient enzymatic oxidation process and supported the presence of two cavities as well as a catalytically important "aromatic cage" formed by F342, Y433, and FAD. The synthetic applicability of CHAOCCH12-C2 was further underscored by the stereoselective synthesis of various enantioenriched 1-benzyl-OHIQ derivatives of potential pharmaceutical importance at a semipreparative scale.
- Chen, Fener,Huang, Zedu,Li, Zhining,Lin, Juan,Wang, Jiaqi,Wang, Zexu,Wu, Xiaofan
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supporting information
p. 5598 - 5614
(2020/05/19)
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- Method for preparing levallorphan tartrate
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The invention provides a method for preparing levallorphan tartrate and belongs to the technical field of drug and chemical synthesis. The method takes methoxyphenylacetic acid and 2-(cyclohexenyl)ethylamine as initial raw materials, and comprises nine reaction steps such as acylation condensation, Bischler-Napieralski ring formation reaction, imine reduction, ether bond hydrolysis, resolution, N-alkylation, Grewe cyclization reaction, and salifying. According to the method, the levallorphan tartrate and each intermediate can be obtained at high yield and high purity, and the method can serve as an industrial method for performing large-scale production.
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Paragraph 0015
(2017/08/29)
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- A process for preparing dextromethorphan method
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The invention relates to a novel method for preparing dextromethorphan. When the method is used for preparing an intermediate (+)-1-(4-methoxy) benzyl-1,2,3,4,5,6,7,8-hexahydroisoquinoline (VI), a catalytic reducing method is adopted to carry out chiral reduction on 1-(4-methoxy) benzyl-3,4,5,6,7,8-hexahydroisoquinoline (VI), so that the intermediate is prepared with high selectivity. The novel method disclosed by the invention can cancel complex operations such as chiral resolution, is simple to operate, gentle in reaction condition, short in total time, wide in material source, and very suitable for industrially producing dextromethorphan.
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Paragraph 0177-0179
(2018/02/04)
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- A facile microwave assisted synthesis of spiro-1,3-oxazines from N-(2-(cyclohex-1-en-1-yl)ethyl)amides
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A mild and efficient methodology has been developed for the synthesis of spiro-1,3-oxazine derivatives by the microwave assisted cyclization of N-2-(1′-cyclohexenyl)ethyl-acetamides/benzamides. The reaction was catalyzed by in situ generated trimethylsilyl iodide and featured by its very short reaction time. The starting materials were easily obtained by the condensation of substituted acetic/benzoic acids with 2-(1′-cyclohexenyl) ethyl amine.
- Saikia, Ujwal Pratim,Baruah, Diganta,Pahari, Pallab,Borah, Manash Jyoti,Goswami, Amrit,Konwar, Dilip
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supporting information
p. 4328 - 4330
(2014/07/22)
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- GENERAL ASYMMETRIC SYNTHESIS OF BENZOMORPHANS AND MORPHINANS VIA ENANTIOSELECTIVE HYDROGENATION
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A variety of optically active benzomorphans including metazocine and pentazocine as well as dextromethorphan, a morphinan, are obtainable by using the BINAP-ruthenium(II) catalyzed enantioselective hydrogenation as key operation.
- Kitamura, M.,Hsiao, Yi,Noyori, R.,Takaya, H.
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p. 4829 - 4832
(2007/10/02)
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- Process for the preparation of N-(2-(cyclo-hexen-1-yl)ethyl)-4-methoxybenzeneacetamide
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An improved method for preparing a compound having the formula STR1 which is an intermediate in the preparation of dextromethorphan, the improved method comprises the steps of (A) hydrogenating a compound having the formula STR2 in the presence of a hydrogenation catalyst to obtain a compound having the formula STR3 (B) hydrogenating the product of Step (A) in the presence of a hydrogen treated rhodium catalyst to obtain a compound having the formula STR4 (C) reacting the product of Step (B) with 4-methoxyphenylacetic acid to obtain a mixture of compounds comprising STR5 (D) dehydrating the product mixture of Step (C).
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