- Active site mapping of porcine liver esterase (PLE) and porcine pancreatic lipase (PPL): Stereo and regiochemical outcome of hydrolysis of conformationally constrained esters
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The regio and stereoselectivity of PLE and PPL-catalyzed hydrolysis of a number of conformationally constrained substrates have been studied. The results are discussed based on the existing active site models for the two enzymes.
- Basak,Rudra,Ghosh,Bhattacharya
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p. 974 - 980
(2007/10/03)
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- Copper-Catalyzed Reaction of Terminal Alkynes with Nitrones. Selective Synthesis of 1-Aza-1-buten-3-yne and 2-Azetidinone Derivatives
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Reaction of arylacetylenes with C,N-diarylnitrones using a catalyst system of CuI-dppe (dppe = 1,2-bis(diphenylphosphino)ethane) in the presence of potassium carbonate in DMF predominantly affords the corresponding 1,2,4-triaryl-1-aza-1-buten-3-ynes in good yields.In contrast, the catalytic reaction using CuI in the presence of an excess amount of pyridine as the ligand gives 1,3,4-triaryl-2-azetidinones as the major products.The reaction with aliphatic terminal alkynes in place of arylacetylenes produces the latter products irrespective of the catalyst system used.Asymmetric induction is also observed in the reaction of phenylacetylene with α,N-diphenylnitrone to give 1,2,4-triphenyl-2-azetidinone in the presence of chiral bisoxazoline-type ligands.
- Miura, Masahiro,Enna, Masahiro,Okuro, Kazumi,Nomura, Masakatsu
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p. 4999 - 5004
(2007/10/03)
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- A STEREOCONTROLLED SYNTHESIS OF 3-(1'-HYDROXYETHYL)-2-AZETIDINONES THROUGH TRIMETHYLSILYL TRIFLUOROMETHANESULPHONATE CATALYZED CONDENSATION OF SILYL KETENE ACETAL DERIVED FROM ETHYL 3-HYDROXYBUTYRATE AND IMINE
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The silyl ketene acetal 2, prepared from ethyl 3-hydroxybutyrate, reacted with benzylidene aniline in the presence of trimethylsilyl trifluoromethanesulphonate to furnish in satisfactory yield the β-amino ester 3 as a single diastereomer, which was subseq
- Guanti, Giuseppe,Narisano, Enrica,Banfi, Luca
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p. 4335 - 4338
(2007/10/02)
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- 3-(1'-hydroxyethyl)-2-azetidinones from 3-hydroxybutyrates and N-arylaldimines
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Dianion imine addition, cyclisation reaction between ethyl-3-hydroxybutyrate and the aldimines generates β-lactams with the hydroxyethyl side chain of thienamycin and related β-lactam antibiotics in place. The effects of the N-arylaldimine and the reactio
- Georg,Gill,Gerhardt
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p. 3903 - 3906
(2007/10/02)
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- Stereoselective Synthesis of 3-(1-Hydroxyethyl)-2-azetidinones from 3-Hydroxybutyrates
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Addition of dianions of 3-hydroxybutyrates to benzylideneaniline result in direct formation of trans S*-3-(1-hydroxyethyl)-1,4-diphenyl-2-azetidinone with 95percent diastereoselectivity.Inversion of the configuration at Cα gives the
- Georg, Gunda I.
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p. 3779 - 3782
(2007/10/02)
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