285130-47-4Relevant academic research and scientific papers
Mitsunobu approach to the synthesis of optically active α,α-disubstituted amino acids
Green, Jonathan E.,Bender, David M.,Jackson, Stona,O'donnell, Martin J.,Mccarthy, James R.
supporting information; experimental part, p. 807 - 810 (2009/08/08)
Chiral tertiary α-hydroxy esters of known stereochemical configuration were transformed to α-azido esters by Mitsunobu reaction with HN3. Optimization of this reaction was shown to proceed at room temperature with high chemical yield using 1,1-(azodicarbonyl)dipiperidine (ADDP) and trimethylphosphine (PMe3). Complete inversion of configuration was observed at the α-carbon. Several α,α- disubstituted amino acids were synthesized in high overall chemical yield and optical purity.
Enzyme-catalyzed Reactions, Part 39. A Convenient Synthesis of Optically Active 5,5-Disubstituted 4-Amino- and 4-Hydroxy-2(5H)-furanones from (S)-Ketone Cyanohydrins
Buehler, Holger,Bayer, Andreas,Effenberger, Franz
, p. 2564 - 2571 (2007/10/03)
(S)-Ketone cyanohydrins (S)-2 are accessible by enantioselective HCN addition to ketones 1 by using hydroxynitrile lyase from Manihot esculenta ((S)-MeHNL) as a biocatalyst. Acylation of (S)-2 gave the corresponding (S)-acyloxynitriles (S)-3, which can be cyclized by LHMDS to give 5,5-disubstituted (S)-4-amino-2(5 H)-furanones (S)-4 and (S)-5. Different substituents (H, Me, OBn, OH) in the 3-position of the furanones were introduced by selecting the appropriate acylating agent, which in the case of benzyloxyacetyl chloride led to the novel structure type of 4-amino-3-hydroxyfuranones (S)-5. For the synthesis of 5,5-disubstituted (S)-tetronic acids (S)-8, ketone cyanohydrins (S)-2 were first transformed into the corresponding 2-hydroxy esters (S)-6. Acylation of (S)-6 gave 2-acyloxy esters (S)-7, which, by treatment with LHMDS or LDA, afforded tetronic acids (S)-8 in high yields and enantiomeric excesses. By debenzylation of benzyloxy acetoxy derivatives (S)-8 e,f, the new vitamin C analogues (S)-9a,b were generated. All the described tetronic acid and aminofuranone derivatives were obtained in good chemical yields and without racemization with respect to the starting cyanohydrins (S)-2. ln many cases the enantiomeric purity could be enriched by simple recrystallization (e.g. (S)-4a from 69% ee to >99% ee).
Hippuryl-α-methylphenylalanine and hippuryl-α-methylphenyllactic acid as substrates for carboxypeptidase A. Syntheses, kinetic evaluation and mechanistic implication
Lee, Mijoon,Kim, Dong H.
, p. 815 - 823 (2007/10/03)
(R)- and (S)-Hippuryl-α-methylphenylalanine [(R)- and (S)-Hipp-α- MePhe] and (S)-hippuryl-α-methylphenyllactic acid [(S)-Hipp-α-MeOPhe] were synthesized and evaluated as substrates for carboxypeptidase A (CPA) in an effort to shed further light on the catalytic mechanism of the enzyme. The rate of CPA-catalyzed hydrolysis of (S)-Hipp-α-MePhe was reduced by 105-fold compared with that of (S)-Hipp-Phe, but the hydrolysis rate of (S)-Hipp-OPhe was lowered by only 6.8-fold by the introduction of a methyl group at the α- position. (R)-Hipp-α-MePhe failed to be hydrolyzed initially, then started to undergo hydrolysis in about 2 h at a much reduced rate. The results of present study may be envisioned on the basis of the proposition that while peptide substrate is hydrolyzed via a tetrahedral transition state formed by the attack of the zinc-bound water molecule at the peptide carbonyl carbon, ester hydrolysis takes the path that involves an anhydride intermediate generated by the attack of the carboxylate of Glu-270 at the ester carbonyl carbon. (C) 2000 Elsevier Science Ltd.
