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Concise Chemoenzymatic Three Step Total Synthesis of Isosolenopsin Through Medium Engineering.

Simon RC, Fuchs CS, Lechner H, Zepeck F, Kroutil W - European J Org Chem (2013)

Bottom Line: A short and efficient total synthesis of the alkaloid isosolenopsin and its enantiomer has been achieved.Diastereostelective chemical reduction (H2/Pd/C) of the biocatalytic product gave the target compound.The linear three step synthesis provided the natural product isosolenopsin in diastereomerically pure form (ee > 99%, d.r. = 99:1) with an overall yield of 64%.

View Article: PubMed Central - PubMed

Affiliation: ACIB GmbH, Heinrichstraße 28, 8010-Graz, Austria.

ABSTRACT
A short and efficient total synthesis of the alkaloid isosolenopsin and its enantiomer has been achieved. In the key step, a ω-transaminase catalyzed the regioselective mono-amination of the diketone pentadecane-2,6-dione which was obtained in a single step via Grignard reaction. Initial low conversions in the biotransformation could be overcome by optimisation of the reaction conditions employing suitable cosolvents. In the presence of 20 vol% DMF or n-heptane best results were obtained employing two enantio-complementary ω-transaminases originating from Arthrobacter between 30-40 °C; under these conditions conversions of >99% and perfect stereocontrol (ee > 99%) were achieved. Diastereostelective chemical reduction (H2/Pd/C) of the biocatalytic product gave the target compound. The linear three step synthesis provided the natural product isosolenopsin in diastereomerically pure form (ee > 99%, d.r. = 99:1) with an overall yield of 64%.

No MeSH data available.


Related in: MedlinePlus

Conversions for the monoamination of diketone 3a in the presence of various organic cosolvents employing (R)- and (S)-selective ω-TAs. Reagents and conditions: diketone 3a (6 mg/mL, 25 mm), lyophilised E. coli cells containing overexpressed ω-TA (20 mg), PLP (1 mm), NAD+ (1 mm), ammonium formate (150 mm), D- or L-alanine (500 mm), AlaDH (12 U), FDH (11 U), organic cosolvent, K-phosphate buffer (100 mm, pH 7.0), 30 °C, 24 h in an Eppendorf orbital shaker (700 rpm).
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fig04: Conversions for the monoamination of diketone 3a in the presence of various organic cosolvents employing (R)- and (S)-selective ω-TAs. Reagents and conditions: diketone 3a (6 mg/mL, 25 mm), lyophilised E. coli cells containing overexpressed ω-TA (20 mg), PLP (1 mm), NAD+ (1 mm), ammonium formate (150 mm), D- or L-alanine (500 mm), AlaDH (12 U), FDH (11 U), organic cosolvent, K-phosphate buffer (100 mm, pH 7.0), 30 °C, 24 h in an Eppendorf orbital shaker (700 rpm).

Mentions: Optimisation of Reaction Conditions (Analytical Scale): Lyophilised cells of E. coli containing the corresponding overexpressed ω-TA (20 mg) were rehydrated in potassium phosphate buffer (100 mm at varying pH as indicated in Figures2, 3, 4, and 5) containing PLP (1.0 mm), NAD+ (1.0 mm), ammonium formate (150 mm), FDH (11 U), Ala-DH (12 U) and D- or L-alanine (500 mm) at room temperature for 30 min. Substrate 3a (6 mg, 25 mm, dissolved in the corresponding organic solvent as indicated in Figures2, 3, 4, and 5) was then added and the reductive amination was performed at defined temperature as indicated (Figures2, 3, 4, and 5) in an Eppendorf orbital shaker (700 rpm, vertical position) for 24 h. After the period of time, the reaction was stopped by addition of saturated Na2CO3 (200 μL) and vigorous shaking. The mixture was extracted with EtOAc (3 × 500 μL) and the combined organic layers were dried with MgSO4 and an aliquot was withdrawn for further analysis. Conversions were determined by GC analysis on an achiral phase [column HP-5 (Agilent); carrier gas: hydrogen; temperature program: 100 to 250 °C at 10 °C min–1]: Rt = 8.7 (6a), 10.6 (3a) min. Determination of enantiomeric excess by GC analysis on a chiral phase [column DEX-CB (Agilent; CP-Chirasil); carrier gas: helium; temperature program: 60 °C (1 min), then 6090 °C at 5.0 °C min–1 then 90180 °C at 2 °C min–1]: Rt = 37.23 [(2R)-6a], 37.41 [(2S)-6a] min.


Concise Chemoenzymatic Three Step Total Synthesis of Isosolenopsin Through Medium Engineering.

Simon RC, Fuchs CS, Lechner H, Zepeck F, Kroutil W - European J Org Chem (2013)

Conversions for the monoamination of diketone 3a in the presence of various organic cosolvents employing (R)- and (S)-selective ω-TAs. Reagents and conditions: diketone 3a (6 mg/mL, 25 mm), lyophilised E. coli cells containing overexpressed ω-TA (20 mg), PLP (1 mm), NAD+ (1 mm), ammonium formate (150 mm), D- or L-alanine (500 mm), AlaDH (12 U), FDH (11 U), organic cosolvent, K-phosphate buffer (100 mm, pH 7.0), 30 °C, 24 h in an Eppendorf orbital shaker (700 rpm).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4151137&req=5

fig04: Conversions for the monoamination of diketone 3a in the presence of various organic cosolvents employing (R)- and (S)-selective ω-TAs. Reagents and conditions: diketone 3a (6 mg/mL, 25 mm), lyophilised E. coli cells containing overexpressed ω-TA (20 mg), PLP (1 mm), NAD+ (1 mm), ammonium formate (150 mm), D- or L-alanine (500 mm), AlaDH (12 U), FDH (11 U), organic cosolvent, K-phosphate buffer (100 mm, pH 7.0), 30 °C, 24 h in an Eppendorf orbital shaker (700 rpm).
Mentions: Optimisation of Reaction Conditions (Analytical Scale): Lyophilised cells of E. coli containing the corresponding overexpressed ω-TA (20 mg) were rehydrated in potassium phosphate buffer (100 mm at varying pH as indicated in Figures2, 3, 4, and 5) containing PLP (1.0 mm), NAD+ (1.0 mm), ammonium formate (150 mm), FDH (11 U), Ala-DH (12 U) and D- or L-alanine (500 mm) at room temperature for 30 min. Substrate 3a (6 mg, 25 mm, dissolved in the corresponding organic solvent as indicated in Figures2, 3, 4, and 5) was then added and the reductive amination was performed at defined temperature as indicated (Figures2, 3, 4, and 5) in an Eppendorf orbital shaker (700 rpm, vertical position) for 24 h. After the period of time, the reaction was stopped by addition of saturated Na2CO3 (200 μL) and vigorous shaking. The mixture was extracted with EtOAc (3 × 500 μL) and the combined organic layers were dried with MgSO4 and an aliquot was withdrawn for further analysis. Conversions were determined by GC analysis on an achiral phase [column HP-5 (Agilent); carrier gas: hydrogen; temperature program: 100 to 250 °C at 10 °C min–1]: Rt = 8.7 (6a), 10.6 (3a) min. Determination of enantiomeric excess by GC analysis on a chiral phase [column DEX-CB (Agilent; CP-Chirasil); carrier gas: helium; temperature program: 60 °C (1 min), then 6090 °C at 5.0 °C min–1 then 90180 °C at 2 °C min–1]: Rt = 37.23 [(2R)-6a], 37.41 [(2S)-6a] min.

Bottom Line: A short and efficient total synthesis of the alkaloid isosolenopsin and its enantiomer has been achieved.Diastereostelective chemical reduction (H2/Pd/C) of the biocatalytic product gave the target compound.The linear three step synthesis provided the natural product isosolenopsin in diastereomerically pure form (ee > 99%, d.r. = 99:1) with an overall yield of 64%.

View Article: PubMed Central - PubMed

Affiliation: ACIB GmbH, Heinrichstraße 28, 8010-Graz, Austria.

ABSTRACT
A short and efficient total synthesis of the alkaloid isosolenopsin and its enantiomer has been achieved. In the key step, a ω-transaminase catalyzed the regioselective mono-amination of the diketone pentadecane-2,6-dione which was obtained in a single step via Grignard reaction. Initial low conversions in the biotransformation could be overcome by optimisation of the reaction conditions employing suitable cosolvents. In the presence of 20 vol% DMF or n-heptane best results were obtained employing two enantio-complementary ω-transaminases originating from Arthrobacter between 30-40 °C; under these conditions conversions of >99% and perfect stereocontrol (ee > 99%) were achieved. Diastereostelective chemical reduction (H2/Pd/C) of the biocatalytic product gave the target compound. The linear three step synthesis provided the natural product isosolenopsin in diastereomerically pure form (ee > 99%, d.r. = 99:1) with an overall yield of 64%.

No MeSH data available.


Related in: MedlinePlus