title: Amino acid catalyzed neogenesis of carbohydrates: a plausible ancient transformation.
abstract: Hexose sugars play a fundamental role in vital biochemical processes and their biosynthesis is achieved through enzyme-catalyzed pathways. Herein we disclose the ability of amino acids to catalyze the asymmetric neogenesis of carbohydrates by sequential cross-aldol reactions. The amino acids mediate the asymmetric de novo synthesis of natural L- and D-hexoses and their analogues with excellent stereoselectivity in organic solvents. In some cases, the four new stereocenters are assembled with almost absolute stereocontrol. The unique feature of these results is that, when an amino acid is employed as the catalyst, a single reaction sequence can convert a protected glycol aldehyde into a hexose in one step. For example, proline and its derivatives catalyze the asymmetric neogenesis of allose with >99 % ee in one chemical manipulation. Furthermore, all amino acids tested catalyzed the asymmetric formation of natural sugars under prebiotic conditions, with alanine being the smallest catalyst. The inherent simplicity of this catalytic process suggests that a catalytic prebiotic "gluconeogenesis" may occur, in which amino acids transfer their stereochemical information to sugars. In addition, the amino acid catalyzed stereoselective sequential cross-aldol reactions were performed as a two-step procedure with different aldehydes as acceptors and nucleophiles. The employment of two different amino acids as catalysts for the iterative direct aldol reactions enabled the asymmetric synthesis of deoxysugars with >99 % ee. In addition, the direct amino acid catalyzed C(2)+C(2)+C(2) methodology is a new entry for the short, highly enantioselective de novo synthesis of carbohydrate derivatives, isotope-labeled sugars, and polyketide natural products. The one-pot asymmetric de novo syntheses of deoxy and polyketide carbohydrates involved a novel dynamic kinetic asymmetric transformation (DYKAT) mediated by an amino acid.
authors.affiliation: Department of Organic Chemistry, The Arrhenius Laboratory, Stockholm University, Sweden. accordova@organ.su.se
authors.forename: Armando
authors.initials: A
authors.lastname: Córdova
authors.forename: Ismail
authors.initials: I
authors.lastname: Ibrahem
authors.forename: Jesús
authors.initials: J
authors.lastname: Casas
authors.forename: Henrik
authors.initials: H
authors.lastname: Sundén
authors.forename: Magnus
authors.initials: M
authors.lastname: Engqvist
authors.forename: Efraim
authors.initials: E
authors.lastname: Reyes
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D019143:Evolution, Molecular; D008968:Molecular Conformation; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D000596:Amino Acids; D009844:Oligosaccharides; D012997:Solvents; D014867:Water