Asymmetric organocatalytic formation of protected and unprotected tetroses under potentially prebiotic conditions
Esters of proteinogenic amino acids efficiently catalyse the formation of erythrose and threose under potentially prebiotic conditions in the highest yields and enantioselectivities yet reported. Remarkably while esters of (l)-proline yield (l)-tetroses, esters of (l)-leucine, (l)-alanine and (l)-valine generate (d)-tetroses, offering the potential to account for the link between natural (l)-amino acids and natural (d)-sugars. The effect of pH and NaCl on the yields and enantioselectivities was also investigated and was shown to be significant, with the optimal enantioselectivities occurring at pH 7.
Burroughs, Laurence,Clarke, Paul A.,Forintos, Henrietta,Gilks, James A. R.,Hayes, Christopher J.,Vale, Matthew E.,Wade, William,Zbytniewski, Myriam
experimental part
p. 1565 - 1570
(2012/04/05)
Efficient asymmetric organocatalytic formation of erythrose and threose under aqueous conditions
Esters of proteinogenic amino acids efficiently catalyse the formation of erythrose and threose under aqueous conditions in the highest yields and enantioselectivities yet reported. Remarkably while esters of (l)-proline yield (l)-carbohydrates, esters of (l)-leucine and (l)-alanine generate (d)-carbohydrates, offering the potential to account for the prebiotic link between natural (l)-amino acids and natural (d)-sugars.
Burroughs, Laurence,Vale, Matthew E.,Gilks, James A. R.,Forintos, Henrietta,Hayes, Christopher J.,Clarke, Paul A.
supporting information; experimental part
p. 4776 - 4778
(2010/09/05)
Prebiotic carbohydrate synthesis: Zinc-proline catalyzes direct aqueous aldol reactions of α-hydroxy aldehydes and ketones
Zn-proline catalyzed aldolisation of glycoladehyde gave mainly tetroses whereas in the cross-aldolisation of glycoladehyde and rac-glyceraldehyde, pentoses accounted for 60% of the sugars formed with 20% of ribose. The Royal Society of Chemistry 2005.
Kofoed, Jacob,Reymond, Jean-Louis,Darbre, Tamis
p. 1850 - 1855
(2007/10/03)
Regioselective benzylation of pentitols, tetritols, and some hexitols via their stannyl ether derivatives: Versatile synthesis of monobenzylalditols
The xylitol, ribitol and D-arabinitol were transformed into their tributylstannyl ether derivatives by reaction with bis-tributyltin oxide [(nBu3Sn)2O I] and azeotropic removal of water. Subsequent benzyl etherification, using BnBr with solvent or under free solvent conditions, led regioselectively to primary mono-O-benzylalditol derivatives in satisfactory yields for a direct regioselective synthesis (~ 52%). This etherification when applied to tetritols and some hexitols exhibits similar behaviour. With pentitols, an analogous study carried out with the n-dibutyltin oxide [nBu2SnO (II)] as the activating reagent showed contrasting results as regards regioselectivity.
Halila, Sami,Benazza, Mohammed,Demailly, Gilles
p. 467 - 483
(2007/10/03)
EQUILIBRATION OF ALDITOL ANHYDRIDES IN ACETIC ACID
Dehydration of pentitols in acetic acid containing an acidic catalyst parallels that in aqueous sulfuric acid; 1,4(2,5)-dehydration occurs with inversion of configuration at C-2 or C-4.Acetylated alditols undergo similar processes via intermediates having free hydroxyl groups.Configurational inversion of 1,4- or 1,5-anhydroalditols is attributed to intermediate acyloxonium ions that are also proposed as intermediates in the structural isomerisation.Drastic treatment of each alditol gives equilibrium mixtures.The equilibrium concentrations are used to calculate free-energy differences.
Wisniewski, Andrzej,Gajdus, Jerzy,Sokolowski, Janusz,Szafranek, Janusz
p. 11 - 20
(2007/10/02)
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