174292-11-6Relevant articles and documents
Application of Threonine Aldolases for the Asymmetric Synthesis of α-Quaternary α-Amino Acids
Blesl, Julia,Trobe, Melanie,Anderl, Felix,Breinbauer, Rolf,Strohmeier, Gernot A.,Fesko, Kateryna
, p. 3453 - 3458 (2018/07/30)
We report the synthesis of diverse β-hydroxy-α,α-dialkyl-α-amino acids with perfect stereoselectivity for the α-quaternary center through the action of l- and d-specific threonine aldolases. A wide variety of aliphatic and aromatic aldehydes were accepted by the enzymes and conversions up to >80 % were obtained. In the case of d-selective threonine aldolase from Pseudomonas sp., generally higher diastereoselectivities were observed. The applicability of the protocol was demonstrated by performing enzymatic reactions on preparative scale. Using the d-threonine aldolase from Pseudomonas sp., (2R,3S)-2-amino-3-(2-fluorophenyl)-3-hydroxy-2-methylpropanoic acid was generated in preparative amounts in one step with a diastereomeric ratio >100 favoring the syn-product. A Birch-type reduction enabled the reductive removal of the β-hydroxy group from (2S)-2-amino-3-hydroxy-2-methyl-3-phenylpropanoic acid to generate enantiopure l-α-methyl-phenylalanine via a two-step chemo-enzymatic transformation.
Stereoselectivity in reactions of amino acids catalyzed by pyridoxal derivatives carrying rigidly-attached chirally-mounted basic groups - Transamination, racemization, decarboxylation, retro-aldol reaction, and aldol condensation
Liu, Lei,Rozenman, Mary,Breslow, Ronald
, p. 3973 - 3979 (2007/10/03)
A tetrahydroquinoline ring was used to mount the critical functional groups of pyridoxal, and also two examples of rigidly held chirally mounted basic groups. They were able to selectively catalyze decarboxylation, aldol reaction, and retro-aldol reaction of amino acids rather than transamination, and with stereoselectivity. In the aldol reaction of glycine with acetaldehyde to synthesize threonine and allo-threonine, one of the catalysts reversed its stereoselectivity when the basic group was protonated. The observed stereoselectivities were all consistent with prediction.
